# An-Najah National University

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An-Najah National University
Faculty of Engineering Electrical Engineering Department electrical Loads the first step in the electrical designing for any construction is to estimate the electrical loads This enables the electrical engineering (designer) to know exactly who should the electrical power feed this construction

An-Najah National University
Faculty of Engineering Electrical Engineering Department Electrical Loads Electrical loads in the buildings can be divided into three types:- Electrical loads used in lighting ( illumination system) , different types of lamps) Electrical loads feed the normal sockets and outlets ( used for small electrical devices , TV, radio , washing machine, etc….) Electrical loads that feed the mechanical devices used in the buildings ( elevators , heating system ,cooling system , pumps ,etc)

estimation of the electrical loads used in lighting
An-Najah National University Faculty of Engineering Electrical Engineering Department estimation of the electrical loads used in lighting the estimation of the electrical loads used in lighting is achieved by calculating the sum of the lamps used in the illumination system there are different types of lamps :- Incandescent Lamp Gas-discharge lamps

Old method for Electrical Load estimation in lightings
An-Najah National University Faculty of Engineering Electrical Engineering Department Old method for Electrical Load estimation in lightings this methods assumes that all the lighting system consists of either Incandescent Lamp or florescent lamps or a mixed of them . in the case of using incandescent lamps :- Power(watt/m2) = illuminances (Lux)/2.78 Power(watt/m2) = illuminances (Lux)/11.148 form the above equations it is quite clear that the using of florescent lamps can save power so it is quite important to use them as much as possible. This method is no longer used as it depends on approximations in addition to the fact that there a lot of different types of lamps used these days

An-Najah National University
Faculty of Engineering Electrical Engineering Department example An office with an area of 60 m2, and the illuminance equals 500 lux, calculate the power needed in the cases of using the incandescent lamp and florescent lamps. Answer :- in the case of using candescent lamps :- P= 60* 500 / = watt in the case of using florescent lamps : P= 60* 500 / = 2691 watt power saving using the florescent lamps= = 8072 watt

Unit or Specific Load per Square meter
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit or Specific Load per Square meter To over come the disadvantage of the previous method the “Unit or specific load per square meter” which depends on the natural using of the space in the building. This method give more accurate results than the previous one. Room Type Unit or specific load(watt/m2) Living room (not dark colours for walls) 20-30 Living room (dark colours for walls) 40-50 children room (not dark colours for walls) 30-40 children room (dark colours for walls) 60-70 Sleeping room kitchen 50-60 Working areas Stairs , corridors,

Unit or specific load(watt/m2) theatres 10 banks 21
An-Najah National University Faculty of Engineering Electrical Engineering Department Room Type Unit or specific load(watt/m2) theatres 10 banks 21 Hair dressing shops 32 Worship areas clubs hospitals hotels offices 53 schools Restaurants

ways for energy consumption saving in lights systems
An-Najah National University Faculty of Engineering Electrical Engineering Department ways for energy consumption saving in lights systems using lamps unites with high efficiency which is called “energy saving lamps” which have a high efficiency per watt in addition to the fact that they lasting for long times compared to the normal lamps using lamps unites with low electrical losses on the form of heat which reduce the need of using the cooling systems for the construction. reducing the light losses by using lamp units with low light losses coefficient using lamp units with higher coefficient utilization

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure this method differs than the previous methods in:- 1- it takes into account the shape of the rooms or the space(square,rectangle, etc) 2- it assumes that the lighting system in that room or space is based on the maximum using of the electrical power. This method depends on dividing the building into rooms depending on the nature of using. And for every room or space there is a tables shows base power unit density(UPD) for that space in watt/m2

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure the power needed for lighting a room or a space according to this method is:- Power= Area* Power unit density(UPD)*room factor* space utilization factor(SUF). Power= A* a1* a2 Power: watt Area (A):m2 Power Unit density(UPD): (F):watt/ m2 Room factor : (a1) Space utilization factor :(a2)

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure Power Unit density(UPD): obtained from tables(1.2) Room Type Power unity density Bank 50.59 hospitals 15.07 offices 34.44 buildings 23.68 hotels Libraries 9.69 Schools Shops 40.9

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure Room factor : (a1) Room factor (a1) is a number between 1.0 and 2.0 and its important comes from that it shows the effect of the room or space shape on the lighting system . From table (2.2) Eg 1 :- length of the room is Width is 3.7 and the length is 2.7. the room factor from the table will be 1.8 Eg 2 :- length of the room is Width is 2.4 and the length is 3.4. the room factor from the table will be 1.9 If the shape of the room is not regular we choose a nearest regular shape such that the area of the regular shape is equal to the irregular shape of the room or space

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure Space utilization factor :(a2) The value of the space utilization factor (S.U.F) is between 0.4 and 1.0 . it is depends on the ration between the area of the room or space that is used and the total area of the space or the room. Ratio between the used area and the total area space utilization factor (S.U.F) 1 0.85 0.77 0.55 Up to 0.19 0.4

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure Unlisted areas After calculating the electrical power needed for lighting the rooms it means that we calculate the electrical power needed for lighting all the listed areas. For the unlisted spaces . First : the area of these spaces are calculated and it equals the area of each flat in the building –the area of the listed spaces. The electrical power for the unlisted spaces is then calculated by multiplying its area by 2.15 watt/m2 the total electrical power for lighting the inner area will be sum of the powers needed for listed and unlisted area.

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure The maximum electrical power for the whole building it consists of 1- the electrical power calculated for the inner space of the project(listed and un listed) 2- the electrical power needed for lighting the outside of the project a- the electrical power needed for lighting the outside walls of the project (5% of the electrical power needed for the inner lighting ) b- the entrance of the building and the exit (table 1.2) Unit power density for the inner lighting of the project= power for inner light/ total area of the flats Unit power density for the lighting of the project= power for inner light/ total area of the project

Unit Power density procedure
An-Najah National University Faculty of Engineering Electrical Engineering Department Unit Power density procedure The maximum electrical power for the whole building after calculating the total power for the whole building we multiply this power by factor called demand factor which equals 0.85 in the case of lighting. Unit power density for the inner lighting of the project= power for inner light/ total area of the flats Unit power density for the lighting of the project= power for inner light/ total area of the project

Electrical loads needed for feeding the sockets and outlets
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical loads needed for feeding the sockets and outlets used to feed electrical devices with small power if the devices that connected with socket is already known, then the rated power for that device is considered. if not , then for each socket , we assume that the power for the devices that connected to that socket is between 200 to 250 watt if it is single If it is double socket then we assume the power for that socket is about 350 watt.

Electrical loads needed for feeding the sockets and outlets
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical loads needed for feeding the sockets and outlets Table 5.1 shows the number of sockets needed in each room in the building Form the table the number of sockets needed in kitchen is 4 in addition to a special socket for the cooker unit. The total power needed for feeding the sockets will be then multiply by 0.7 as a demand factor.

Electrical loads needed for feeding the mechanical devices
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical loads needed for feeding the mechanical devices Conditiong unit :- each ton refrigeration needs 1500 watt electrical power. Table 6.1 shows the number of ton refrigerating needed in different types of buildings For the pumps :- the electrical engineering obtained the mechanical Horsepower (HP) needed for each pumps The electrical power =for that pump will be: mechanical Horsepower *746 watt For the Escalator and Electrical Stair the power will be given from the catalogue

An-Najah National University
Faculty of Engineering Electrical Engineering Department Electrical lamps Electrical lamps that used in lighting is divided into two main type:- 1- Incandescent lamps 2- Discharge lamps For the incandescent lamps :- the light is emitted as a result of electrical current passing through a filament , which makes it heated to a high temperature then glowing and luminating . For the discharge lamps:- the light is emitted due to the glowing of the gas atoms between the poles of the lamp.

Electrical lamps Specification of electrical lamps:-
An-Najah National University Faculty of Engineering Electrical Engineering Department The luminous efficacy of a lamp Electrical lamps Specification of electrical lamps:- 1- Luminous flux (lumen) 2- Luminous efficiency ( Lumen/watt) 3- Life time 4- Illumination (Lux) or (Lumen/m2) 5- power , voltage (watt ,V) 6- size of the lamp

Electrical lamps Incandescent lamps 1 – Filament (Tungstun) 2- Bulb
An-Najah National University Faculty of Engineering Electrical Engineering Department The luminous efficacy of a lamp Electrical lamps Incandescent lamps 1 – Filament (Tungstun) 2- Bulb 3- Base 4- inert gas or empty volume

Electrical lamps Incandescent lamp
The luminous efficacy of a lamp An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Incandescent lamp the current is fed from the electrical source to the filament using the base when the current pass through a filament, its temperature is increased and after a short time it is becomes glowing and emitting the light. carbon used to be used in the filament , but now a days , Tungstun is used in filament and sometimes some elements such as AL, K, SI are added to Tunstun to improve the hardness of the filament luminous efficiency of the incandescent lamps increases as power of that lamps increase . For example, a lamp with power 150 watt give more illumination in a percentage of 34% than using three 50 watt lamps.

Electrical lamps Incandescent lamp
The luminous efficacy of a lamp An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Incandescent lamp the tungstun incandescent lamps are used a lot because of:- 1- it is found in a lot of shapes (table 2.3) 2- the quality of light (suitable for the eye) 3- is very cheap The lifetime for the incandescent is about 1000 hour, The luminous flux of the incandescent lamps is directly related to the applied voltage on the lamp. Table 3.3 shows the relation between the luminous flux , voltage, and the lifetime .

Electrical lamps Incandescent lamp The end life of the Tungstun lamps
The luminous efficacy of a lamp An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Incandescent lamp The end life of the Tungstun lamps The melting of the filament is the indication of the end life of the Tungstun incandescent lamps Due to a defect in a position on the filament , a hot-spot is formed on it, and the temperature of the on that position at beginning will be higher than other position on the filament. the high temperature makes the Tungstun to evaporate. All these process happened at the beginning of the lighting . The evaporated Tungstun is stuck on the inner surface of the bulb making a black colour to appears on the bulb surface.(blackening).

Electrical lamps Incandescent lamp The end life of the Tungstun lamps
The luminous efficacy of a lamp An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Incandescent lamp The end life of the Tungstun lamps The blackening phenomena appears only in the Tungstun lamps where the bulb is evacuated from the air To overcome the blackening phenomena , a Halogen Lamps are used where one of the following halogen is used (Cl, Br, I, F) in addition to the inert gas. This halogen helps to return back the evaporated Tungstun. they are more efficient than incandescent bulbs using only half the energy to produce the same light output and last twice as long The halogen lamps are used for specific applications where a low voltage and clear light is needed like , cinema , projectors, theaters, cars lamps , in TVs

Electrical lamps Discharge lamps
The luminous efficacy of a lamp An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Discharge lamps the principal operation of the discharge lamps is based on an electrical discharge in the atoms of the inert gas or the vapour of metals or a mixed of them. this results on some visible lights It is divided into two types:- 1- low pressure discharge lamps (Neon , Florescent) 2- high pressure discharge lamps (Soduim and mercury )

Electrical lamps Florescent lamps
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Florescent lamps The current passes through the circuit heating up the filament in each electrode, which are located at both ends of the tube. The heated electrodes in addition to the high voltage applied to two ends of the lamps cauasing electrical discharge (ionizing the gas(argon)). The mercury vapor becomes "excited" and it generates radiant energy, mainly in the ultraviolet range. This energy causes the phosphor coating on the inside of the tube to fluorescent, converting the ultraviolet into visible light.

Electrical lamps Florescent lamps
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Florescent lamps in order to obtain a light from florescent lamps, the following things should be happened 1- electrical discharge 2- tranforming the ultraviolet radiated energy to a visible light

Electrical lamps Power of the lamps(watt) Incandescent lamps
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Power of the lamps(watt) Incandescent lamps 1- general service lamps (15 to 250 watt) 2- projectors ( ) watt 3- halogen Lamps ( ) watt 4- table lamps for specific use (15- 50)watt (positional use) Florescent lamps 1- general (15-80) watt 2- special types ( ) watt 3- table lamps (4-31) watt (positional use)

Electrical lamps Mercury Lamps 1- general (80-1000) watt Soduim Lamps
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Mercury Lamps 1- general ( ) watt Soduim Lamps 1- low pressure (35-180) watt 2- high pressure ( ) watt

Electrical lamps Lifetime Incandescent Lamps :- 1- Genral (1000 ) hour
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Lifetime Incandescent Lamps :- 1- Genral (1000 ) hour 2- projector ( ) hour 3- Halogen (2000) hour Florescent :- 1- (15-80 ) watt : hour 2- ( ) watt: hour 3- (4-13) watt: hour Mercurry :-7500 hour Soduim : hour CFL :- ( )

Electrical lamps Luminous efficiency ( Lumen/watt) Lamp type
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Luminous efficiency ( Lumen/watt) Lamp type Luminous efficiency Incandescent 25 Florescent 80 Mercury 60 Soduim (Low pressure) 185 Soduim (high pressure) 140 CFL (sl, pl) (compact florescent lamps) (energy saving lamps) 75-95

Electrical lamps Energy saving Lamps (CFL)
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Energy saving Lamps (CFL) It is new lamps and comes to replace the traditional lamps (florescent and incandescent) It has the following characteristics:- 1- Low consumption of energy 2- long life time (5000 hour) 3- high luminous efficiency (50 lumen/watt) 4- have a small size.

Electrical lamps Comparison between incandescent lamps and CFL lamps
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Comparison between incandescent lamps and CFL lamps 1- Life time Size * incandescent 1000 hour * bigger * CFL 5000 hour * smaller 2- power weight * incandescent :75 watt * bigger * CFL : 18 watt * smaller 3- luminous flux : cost * incandescent : 900 lumen * less * CFL : 90 lumen * more 4- luminous efficiency * incandescent : 12 lumen/watt * CFL 50 lumen/watt

Electrical lamps Comparison between incandescent lamps and CFL lamps
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical lamps Comparison between incandescent lamps and CFL lamps Eg:- compare between incandescent lamps (75 watt) and CFL lamp with power (18 ) watt . If The price of incandescent is JD and the price of the florescent is 4.5 JD and the price of the kwh is 0.04 JD assuming that both kamps will work 5000 hour No of incandescent lamps =5000/1000=5 No if CFL lamps =1 The price of the incandescent lamps =5*0.2 = 1 JD The price of the CFL lamps = 4.5 JD The power consumed by incandescent in 5000 hour in Kwh= 5000 *75/1000 = 375 kwh The price of the kwh = 375 * 0.04 = 15 JD Total for incandescent = 15+1= 16 JD Kwh for CFL = 5000*18/1000= 90 Price of kwh = 90 *0.04= 3.6 JD Total price for CFL = = 8.1 JD Saving = = 7.9 JD

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations The objective of performing the lighting calculations is to determine the type, power and Distribution the lamps unites This needs the to know the illumination needed in the sapce depinding on the natural use of the space the method that we want to use here is called Lumen method

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method This method depends on using the utilization factor assuming that the illumination is distributed Regularly in all directions in the space. N= Em.A/n*Fl*ku*kn N= no of lamp unites needed to obtain the desired illumination Em= illumination (obtained from tables A = area n= no of lamps in the unite Fl= luminous flux for the lamp (lumen) Ku= utilization factor Kn= maintenance factor

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method Kn= maintenance factor The maintenance factor depends on the situation of space :- It is value obtained from the table below:- Room situation Maintenance factor Normal 0.8 Dirty 0.7 Very dirty 0.6

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method Ku= utilization factor The utilization factor depends on the dimensions of the room . Kr Utilization factor % 0.6 35 0.8 44 1 51 1.25 58 1.5 64 2 72 2.5 77 3 81 4 85 5 89 >5 90

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method Ku= utilization factor Where kr is the room index and it is calculated as follows:- Kr= L*w/Hm(L+w) Where Kr:- room index L :- length of the room w:- width of the room Hm:- the high of the lamp unit from the surface of works in m

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method kr If the height of the room is H , and the height of the woorking surface from the ground of the room is Hp, and the lamp unit is hanged a distance HL from the ceiling then Hm=H-HL-Hp Usually Hp = 75 cm except it is given a value different than that.

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method eg an office wit dimensions = 8m length , 5 m width and 3 m height . Calculate the number of unit lamps needed for illumination. Solution:- we use lumilux flourescent lamps from table 16.3 page 111 where luminous flux = Fl=L=3450 lumen . Ilumination =500 lux. Page 275. Maintenance factor=kn= 0.8 Utilization factpr kr= L*w/Hm(L+w). HL=0 Hp=0.75 m Hm= =2.25 m Kr=8*5/(8+5)*2.25=1.37 We choose kr= /2=0.61 N=500*8*5/2*3450*0.61*0.8=5.59 = 6 units

Lighting calculations
An-Najah National University Faculty of Engineering Electrical Engineering Department Lighting calculations Lumen Method eg an office wit dimensions = 8m length , 5 m width and 3 m height . Calculate the number of unit lamps needed for illumination. Solution:- we use lumilux flourescent lamps from table 16.3 page 111 where luminous flux = Fl=L=3450 lumen . Ilumination =500 lux. Page 275. Maintenance factor=kn= 0.8 Utilization factpr kr= L*w/Hm(L+w). HL=0 Hp=0.75 m Hm= =2.25 m Kr=8*5/(8+5)*2.25=1.37 We choose kr= /2=0.61 N=500*8*5/2*3450*0.61*0.8=5.59 = 6 units

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors the electrical conductors that are used in electrical installation are usually made from AL or CU or a mixed of them. The difference between the AL and CU is that the specific resistance for the Cu is less than that in AL This means that a cable with bigger radius is needed in the case of AL compared to Cu to conduct the same current.

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors Conductor resistances and the factors that affect it Conductors have a high conductivity due to the existence of a high no of free electrons or in other meanings its electrical resistance is very low :- ρ=1/σ Where ρ is the resistivity and σ is the conductivity of the conductors. The resisivity is an indication of the quality of the materials as the resistivity is wanted to be as small as possible .

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors The resistivity of the conductors is affected by the temperature according to the following formulas:- ρt=ρ0(1+ℓ (T-T0) Where ρt is the resistivity at temperature T ρ0 is the resistivity at 250 ℓ is the thermal expansion coefficient for the conductors at 250

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors thermal expansion coefficient for the conductors Material Thermal expansion coefficient silver 0.0038 Copper Aluminium Nickel 0.006 Iron Platinum 0.0025 NI mixture 0.0001

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors The resistance of any cable is given as:- R= ρL/A Where R is the resistance ρ resistivity L length of the cable A area of the cable From the above equations the resistance depends on:- 1-the conductor type (AL ,Cu) 2- length of the cable 3- area of the cable 4- temperature It is meant by temperature :- 1- the temperature of the space around the conductors 2- the temperature of the cable itself which is produced by the current passing in the cable

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors Ampacity of cables Ampacity is defined as the maximum amount of electrical current which a cable can carry before sustaining immediate or progressive deterioration 1- its insulation temperature rating; 2- the electrical resistance of the cable material; 3-frequency of the current, in the case of alternating current; 4 - ability to dissipate heat, which depends on cable geometry and its surroundings; 5- ambient temperature.

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors How to calculate the cross section area of the cable 1- calculate the designing current in the circuit ore part of the circuit 2- according to that , the protection for the circuit is selected 3- the choosing of the cross sectional area of the cable will be according to I cable > I protection > I design

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors Coloures for electrical conductors Current IEC Protective earth (PE) Green/yellow bi-colour Neutral (N) Blue Single phase: Live (L) Three phase: L1 Brown Three phase: L2 Black Three phase: L3 Grey

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors Area of Conductor Resistance at 20°C Max. ohm/km Current Rating (Amp.) 0.05 39.00 4 0.75 26.00 7 1.0 18.10 11 1.5 12.10 14 2.5 7.41 19 4.0 4.95 26 6.0 3.30 33 10.0 1.910 45 16.0 1.210 60 25.0 0.780 75 35.0 0.554 95 50.0 0.386 125

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors Drop voltage calculations Voltage drop = V1 – V2 =2(I1*r1 +I2*r2+I3*r3+I4*r4) I1,2,3,4 are the currents r1,2,3,4 are the branches resistances Let us assume I1=i1+i2+i3+i4 I2=i2+i3+i4 I3=i3+i4 I4= i4

Electrical Conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical Conductors Drop voltage calculations Let us assume R1=r1+r2+r3+r4 R2=r2+r3+r4 R3=r3+r4 R4= r4 Voltage drop = 2(i1*R1+i2*R2+i3*R3+i4*R4) =2∑iαR α As R=ρL/A Voltage drop = 2 ρ/A ∑IL A= (2 ρ/voltage drop) ∑IL

Sockets connections 220 V -50 Hz N P An-Najah National University
Faculty of Engineering Electrical Engineering Department Sockets connections 220 V -50 Hz N P

Switch connections (2 lamps in series with single switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Switch connections (2 lamps in series with single switch 220 V -50 Hz N P

Switch connections (2 lamps in parallel with single switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Switch connections (2 lamps in parallel with single switch 220 V -50 Hz N P

Switch connections (2 lamps with double switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Switch connections (2 lamps with double switch 220 V -50 Hz N P

Switch connections (2 lamps with double switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Switch connections (2 lamps with double switch 220 V -50 Hz N P

Switch connections (2 lamps with double switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Switch connections (2 lamps with double switch 220 V -50 Hz chandelier N E P

Switch connections (2 lamps with double switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Switch connections (2 lamps with double switch 220 V -50 Hz E N L

Sockets connections 220 V -50 Hz N E P An-Najah National University
Faculty of Engineering Electrical Engineering Department Sockets connections 220 V -50 Hz N E P

Sockets connections N E P An-Najah National University
Faculty of Engineering Electrical Engineering Department Sockets connections N E P

lighting 2 lamps from 3 different places
An-Najah National University Faculty of Engineering Electrical Engineering Department lighting 2 lamps from 3 different places 220 V -50 Hz E N L

Bell with push button switch
An-Najah National University Faculty of Engineering Electrical Engineering Department Bell with push button switch N E P

Meausring devices A V Kwh N E P V A An-Najah National University
Faculty of Engineering Electrical Engineering Department Meausring devices A V Kwh N E P V A

Circuit breakers Protect from :- 1- short circuit 2- over load
An-Najah National University Faculty of Engineering Electrical Engineering Department Circuit breakers Protect from :- 1- short circuit 2- over load 3- short circuit and over load Current ratings of circuit breakers : 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A and 100 A instantaneous tripping current, that is the minimum value of current that causes the circuit-breaker to trip without intentional time delay (i.e., in less than 100 ms), expressed in terms of In Type Instantaneous tripping current B above 3 In up to and including 5 In C above 5 In up to and including 10 In D above 10 In up to and including 20 In K above 8 In up to and including 12 In

Circuit breakers Types of circuit breaker 1- thermal circuit breaker
An-Najah National University Faculty of Engineering Electrical Engineering Department Circuit breakers Types of circuit breaker 1- thermal circuit breaker 2- magnetic circuit breaker 3- thermal and magnetic circuit breaker In choosing circuit breakers we should consider the following 1- ICB>= maximum load current 2- VCB> = V supply 3- Ibreaking capacity > 1.2 Isc MCB :- miniature circuit breaker MCCB :- moulded case circuit breaker (63AMP (min.))

An-Najah National University
Faculty of Engineering Electrical Engineering Department Circuit breakers No of units lamps in each feeder should be less than 9 No of sockets in each feeder should be less than 5 if it is 2 A and less than 3 if it is 5 A socket the circuit breaker for the lamp units feeder is 10 A and the cross section of wire is 1.5 mm2 The circuit breaker for the socket feeder is 16 A and the cross section of the wire is 2.5 mm2 There should be feeder for the kitchen and at least spare feeder

RCD single phase (residual-current device)
An-Najah National University Faculty of Engineering Electrical Engineering Department RCD single phase (residual-current device) 2* 40 A, 0.03 A

RCD 3 phases (residual-current device)
An-Najah National University Faculty of Engineering Electrical Engineering Department RCD 3 phases (residual-current device) 4* 40 A, 0.03 A

Many flats in building (main distribution board
An-Najah National University Faculty of Engineering Electrical Engineering Department Many flats in building (main distribution board KwH KwH KwH 3 phase supply

Many flats in building (main distribution board
An-Najah National University Faculty of Engineering Electrical Engineering Department Many flats in building (main distribution board 5*16mm2 xlpe fourth floor DB-F4 5*16mm2 xlpe Third floor DB-F3 5*16mm2 xlpe second floor DB-F2 5*16mm2 xlpe first floor DB-F1 5*16mm2 xlpe Ground floor DB-GF Basement 1 5*16mm2 xlpe DB-B1 Basement 2 KwH DB-B2 5*16mm2 xlpe 3 phase supply

Main DSB From mains 3 * 160 A RCD 160 A 30 mA DB-B2 5*16mm2 DB-B1
An-Najah National University Faculty of Engineering Electrical Engineering Department Main DSB From mains KwH 3 * 160 A RCD 160 A 30 mA DB-B2 5*16mm2 DB-B1 5*16mm2 3 * 63 A DB-GF 5*16mm2 3 * 63 A DB-F1 5*16mm2 3 * 63 A DB-F2 5*16mm2 3 * 63 A DB-F3 5*16mm2 3 * 63 A DB-F4 5*16mm2 3 * 63 A 3 * 63 A

Basement 2 from DB-B2 3 * 63 A RCD 63 A 30 mA light 3*1.5mm2 10 A
An-Najah National University Faculty of Engineering Electrical Engineering Department Basement 2 from DB-B2 3 * 63 A RCD 63 A 30 mA light 3*1.5mm2 10 A light 3*1.5mm2 10 A light 3*1.5mm2 10 A light 3*1.5mm2 10 A socket 3*2.5mm2 16 A socket 3*2.5mm2 16 A socket 3*2.5mm2 16 A spare 3*2.5mm2 16 A

Many flats in building (main distribution board
An-Najah National University Faculty of Engineering Electrical Engineering Department Many flats in building (main distribution board 3*16mm2 xlpe fourth floor KwH DB-F4 3*16mm2 xlpe Third floor KwH DB-F3 3*16mm2 xlpe second floor KwH DB-F2 3*16mm2 xlpe first floor KwH DB-F1 3*16mm2 xlpe DB-GF Ground floor KwH Basement 1 3*16mm2 xlpe KwH DB-B1 KwH Basement 2 DB-B2 3*16mm2 xlpe 3 phase supply

Many flats in building (main distribution board
An-Najah National University Faculty of Engineering Electrical Engineering Department Many flats in building (main distribution board 3*16mm2 xlpe fourth floor DB-F4 3*16mm2 xlpe Third floor DB-F3 3*16mm2 xlpe second floor DB-F2 3*16mm2 xlpe first floor DB-F1 3*16mm2 xlpe Ground floor DB-GF Basement 1 3*16mm2 xlpe DB-B1 Basement 2 DB-B2 KwH KwH KwH KwH KwH KwH KwH 3 phase supply

Main DSB From mains 3 * 160 A RCD 160 A 30 mA DB-B2 3*16mm2 DB-B1
An-Najah National University Faculty of Engineering Electrical Engineering Department Main DSB From mains KwH 3 * 160 A RCD 160 A 30 mA DB-B2 3*16mm2 DB-B1 3*16mm2 1 * 63 A DB-GF 3*16mm2 1 * 63 A DB-F1 3*16mm2 1 * 63 A DB-F2 3*16mm2 1 * 63 A DB-F3 3*16mm2 1 * 63 A DB-F4 3*16mm2 1 * 63 A 1 * 63 A

Basement 2 from DB-B2 1 * 63 A RCD 63 A 30 mA light 3*1.5mm2 10 A
An-Najah National University Faculty of Engineering Electrical Engineering Department Basement 2 from DB-B2 1 * 63 A RCD 63 A 30 mA light 3*1.5mm2 10 A light 3*1.5mm2 10 A light 3*1.5mm2 10 A light 3*1.5mm2 10 A socket 3*2.5mm2 16 A socket 3*2.5mm2 16 A socket 3*2.5mm2 16 A spare 3*2.5mm2 16 A

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories the electrical load in the factories depends mainly on the technological process used in the factory As the industrial process is determined in the planning design for the factory , it is possible to use the electrical information about the loads directly from the company that designs the machines The electrical installation in the factories consists of the following elements:- 1- main distribution board 2- feeders 3- auxiliary distribution boards and circuit breakers

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories Main distribution boards connected with the main supply coming from the electrical distribution company and distributed from it the feeders to auxiliary distribution boards it consists of :- 1- mean switch (circuit breaker) :- disconnect the distribution board from the electrical power and for protection it can be either air switch or oil siwtch 2- bus-bars :- one bus-bar for each phase ,N ,E 3- auxiliary switches 4- instrumentation devices (power , A , V, f)

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories Auxiliary distribution boards

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories General Notes about electrical installation in factories there are different types of distribution boards either single phase or 3 phase and it can be designed to be used outside the factory or inside it in chosing the distribution boards . It is better to chose a place easy to be reached and in the middle of the electrical loads as this will reduce the material used in the installation and reduce the voltage drops It better that the electrical installation in the factories to be clear to make the maintenance easy The cables and the sockets should be designed to carry the short circuit current for short time complete information for safty procedures and the electricla loads on eachD

Electrical distribution in factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical distribution in factories radial distribution ring system voltage drop is less , more reliable Both radial and Ring system

Electrical distribution in factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical distribution in factories substations in factories it is recommended to choose the substation to be near the centre of electrical loads in order to reduce the cost of the electrical netwrok and the no of circuit breaker and protection devices. y(m) load 2 Xo= sum(pi *xi)/sum(pi) yo= sum(pi *yi)/sum(pi) load 1 load 3 x(m)

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories Transformers consist of : 1- core 2- windings 3- cooling equipment a- radiators b- cooling fans c- oil 4- main tank :- a metal tank full of oil in which the windings and core exist 5- Tap changers :- to change the voltages of the transformers to meets the change in the voltages and loads in the electrical network off load:- the transformer needs to disconnect from the network to change the connection of the tap changer oil load:-no need to disconnect the transformer from the network usually in the on load a special devices (relays) is used to regulate the voltage automatically 6- auxiliary devices a- measurement instruments b- protection devices

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories Transformers in parallel conditions to operate 2 transformers in parallel :- 1- have the same voltage ratio 2- have the same voltage impedance 3- same vector groups star-star , delta-delta, star-delat, , delta-star, Group I    - (0°) - delta/delta, star/star Group II   - (180°) - delta/delta, star/star Group III  - (-30°) - star/delta, delta/star Group IV   - (+30°) - star/delta, delta/star (Minus indicates LV lagging HV, plus indicates LV leading HV)

Electrical installation In factories
An-Najah National University Faculty of Engineering Electrical Engineering Department Electrical installation In factories Selection of Transformers Sn> Scal/Kover Sn : the nominal capcity of the transformer Scal :calculated capcity of the load Kover : over load factor at each transformer Where Kover =function (Kl,tmax) Kl- load curve factor Tmax- max time overload operation transformer Kl=S average/S max= P average/Pmax P max A time Paverage= A/24 Kover K load 1.2 0.85 1.15 1.1 0.9 1.05 0.95 1 1 time

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system earting is the electrical connection between the metal parts that are not carrying electrical current in normal conditions with the earth. It is important in earthing system to look at the earthing system at the source of the electrical power and at the consumer There is a special symbols to refer to the earthing system in both sides the first letter refers to the earthing system at the electrical source and there are two letters used for that:- a- T:- refers that one point or more than one point are connected directly to the earth (Terre) b- I :- refers to that the electrical power source is either not connected to the earth or connected to the earth through fault limiting impedance (isolated).

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system the second letter refers to the earthing system at the consumer and there are two letters used for that:- a- T:- all the metal parts that are not carrying electrical current in normal condition are connected directly to the local earth b- N :- all the metal parts that are not carrying electrical current in normal condition are connected directly to the earthing system at the source The third and fourth letters refers to the earthing system connections at the source a- S :- N and and E are sperated b- C:- E and N are one cable

Earthing system TN earthing system An-Najah National University
Faculty of Engineering Electrical Engineering Department Earthing system TN earthing system the electrical source is connected directly with earth and the metal parts that are not carrying electrical current in normal conditions at the consumer are connected to the earthing system at the source. Depending on the neutral and earth connections , there are three types of TN earthign system:- 1- TN-S :- the earthing system at the source is connected directly with earth (T). The metal parts at the consumer are connected to the earthing system at the source (N) . The neutral and the earth are sperated . Nablus

Earthing system TN earthing system An-Najah National University
Faculty of Engineering Electrical Engineering Department Earthing system TN earthing system 1- TN-C-S :- the earthing system at the source is connected directly with earth (T). The metal parts at the consumer are connected to the earthing system at the source (N) . The neutral and the earth are connected at the source and separated at the consumer

Earthing system TN earthing system An-Najah National University
Faculty of Engineering Electrical Engineering Department Earthing system TN earthing system 1- TN-C :- the earthing system at the source is connected directly with earth (T). The metal parts at the consumer are connected to the earthing system at the source (N) . The neutral and the earth are connected

Earthing system TT earthing system (Jerusalem)
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system TT earthing system (Jerusalem) the earthing system at the source is connected directly with earth (T). The metal parts at the consumer are connected directly to the earth at the consumer . The neutral and the earth are connected

Earthing system IT earthing system An-Najah National University
Faculty of Engineering Electrical Engineering Department Earthing system IT earthing system the earthing system at the source is not connected directly with earth (T) but connected through isolation (I). The metal parts at the consumer are connected directly to the earth at the consumer . The neutral and the earth are connected

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system TN networks save the cost of a low-impedance earth connection at the site of each consumer. Such a connection (a buried metal structure) is required to provide protective earth in IT and TT systems. TN-C networks save the cost of an additional conductor needed for separate N and PE connections. However, to mitigate the risk of broken neutrals, special cable types and lots of connections to earth are needed. TT networks require proper RCD protection.

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system Fault path impedance If the fault path between accidentally energized objects and the supply connection has low impedance, the fault current will be so large that the circuit overcurrent protection device (fuse or circuit breaker) will open to clear the ground fault. Where the earthing system does not provide a low-impedance metallic conductor between equipment enclosures and supply return (such as in a TT separately earthed system), fault currents are smaller, and will not necessarily operate the overcurrent protection device. In such case a residual current detector is installed to detect the current leaking to ground and interrupt the circuit.

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system Earthing system components:- 1- electrodes (under gorund) 2- cable connecting the electrode with the earthing bus-bar 3- earthing bus-bar 4- conductors connecting the earthing bus-bar with the metal parts that are not carrying any currents in normal operation Conductor connecting earth bus-bar with metal parts not carrying any currents Earth bus-bar Conductor connecting earth bus-bar with electrode Ground electrode

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system resistivity for the soil the electro physical characteristics for the soil depends on the resistivity of the soil the resistivity of the soil is the resistance of one cube of that soil whose dimensions are 1m x 1m x 1m This resitivity equals :- ρ=r F/L (ohm.m) r:- the resistance of a specific volume of soil whose area is F m2 and whose length is L m

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system resistivity for the soil the resistivity of the soil depends on the followings :- 1- the wetness in the soil:- the resistivity of the soil is reduced significantly with the increase of the wetness of the soil 2- the physical structure of the soil:- the differences in physical structure of the soil leads to differences in the resitivities of the soils : clay soil has less resitivty than that of the dry sand and rocks 3- the chemical structure of the soil :- whether the soil contains metals or salts . The resitivty of the soil is reduced if the salts in the soil is increases. 4- the thermal degree of the soil :-the rising of the thermal degrees of the soil will increase the resitivity of the soil

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system charcteritics that should be found in the soil to be a good earthing system:- 1- low electrical resistivity 2- good resistance against the rust 3- the ability to carry high electrical currents for many times 4- the ability to sustain the above characteristics fro at least 30 years To obtain a good earthing , the following factors should be found:- 1- low resistivity for the soil 2- a wetness soil 3- the temperature of the soil is higher than the freezing temperature

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system Electrodes:- It metal rods buried under the ground . It is used to connect the metal parts that are not carrying any currents in normal conditions with the ground. it should have the following characteristics 1- has a conical shape in order to make it easy to be buried under the ground 2- has a high mechanical solidity 3- high resistance to rust 4- the ability to high a high current at fault conditions length of the electrodes between ( 2.5 – 5 m) it usually made of 1- copper clad steel 2- solid copper 3- galvanized steel 4- stainless steel

Earthing system Vertical Electrodes:- An-Najah National University
Faculty of Engineering Electrical Engineering Department Earthing system Vertical Electrodes:- the resistance of the vertical electrodes are calculated through the following formula:- r =ρ /l Where ρ is the resistivity of the soil ( ohm.m) and L is the length of the electrode Horizontal bar:- It usually connects the vertical electrodes together and it is either thin plates or circular conductors The resistance of this horizontal plates does not depend on the their width or thickness but only depends on the length of this plates and the depth at which they are buried at . The depth of these horizontal plates is 0.6m and 0.7m. The resistance of this bars are calculated through :- r= (ρ/4)*sqrt(π/A) Ρ:- resistivity of the soil in ohm.cm A :- area of the bar(cm2) If the resitance of the bar is high then many bars are connected in parallel to reduce the total resitance of the horizantal bars

Earthing system water installation An-Najah National University
Faculty of Engineering Electrical Engineering Department Earthing system water installation In the past the water pipes were used as electrodes for the earthing system The resistance of the electrical pipes is between 0.2 to 1 ohm for a soil has resitivity of 10 ohm. M Nowadyas , the water pipes are not allowed to be used as the only source for the earthing system as a result of increasing use of the plastic pipes instead of metal ones it is preferred to connect the earthing system with the water installation in the construction

Earthing system utilization factor of the electrodes
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system utilization factor of the electrodes Usually the earthing system is consist of more than one vertical electrode connected with each other Each electrode will affect the other if the distance between the electrodes is not enough This will affect the total resistance of the electrodes if the distance between the electrode is big enougth then the total resistance of electrodes will be:- Re= Ro/n Re :- earth resitance Ro:- the resitance of the electrode In parctical we cannot make the desitance between the electrode very big as this requires a big areas Becaue of that we should consider the utilization factor when calculating the earth resitance. The utilization factor is a no to consider the effect of electrodes on each others. ſ= Ro/Re and it value is less than 1. Re= Rh/ ſh for horizantal electrodes Re =Rv/ ſv.n for vertical electrodes

Earthing system utilization factor of the electrodes
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system utilization factor of the electrodes Usually the earthing system is consist of more than one vertical electrode connected with each other Each electrode will affect the other if the distance between the electrodes is not enough This will affect the total resistance of the electrodes if the distance between the electrode is big enougth then the total resistance of electrodes will be:- Re= Ro/n Re :- earth resitance Ro:- the resitance of the electrode In parctical we cannot make the desitance between the electrode very big as this requires a big areas Becaue of that we should consider the utilization factor when calculating the earth resitance. The utilization factor is a no to consider the effect of electrodes on each others. ſ= Ro/Re and it value is less than 1. Re= Rh/ ſh for horizantal electrodes Re =Rv/ ſv.n for vertical electrodes

Earthing system reducing the earth of the soil
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system reducing the earth of the soil there is two ways to reduce the resistivity of the soil 1- by using electrodes buried deeply in the ground 2- processing the soil Processing the soil is done through adding one of the following salts :- 1- magnesium sulphate 2- copper sulphate 3- carbon or coal 4- Iron filling Eg adding 10 kg from salt to the soil will reduce its resistivity is 80% Usually it needs about kg from salt for processing the soil around the vertical electrode and this will reduce the resistivity of the soil by 2 to 6 times.

Earthing system Earthing conductors
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system Earthing conductors it is the conductors connected between the electrodes and the earth terminal (busbar) Usually the copper or coated steel conductors are used as the earthing conductors copper 16 mm2 (protected against rust) Steel 16 mm2 (protected against rust) copper 25 mm2 (not protected against rust) Steel 50 mm2 (not protected against rust)

Earthing system protective earth
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system protective earth Lowest area of the protective earth in mm2 Area of the phase conductor(s) s S<= 16 16 16<S<=35 s/2 S>35

Earthing system earthing calculation
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system earthing calculation the meaning of the earth calculation is to know the no of electrodes and its type and the way its distributed in order to get the desired earth resistance . The procedures are :- 1- calcuated the single phase short circuit and then calculate the earth resistance. 2- measure the earth resisitnce in the place 3- provisionaly specify the earth system . Like to be consist of no of vertical eelctrodes distributed in one line and connected through a horizantal earth busbar . Or in aclosed shape . 4- calculate the resitance of the vertical electrode using r=resitivty /l No of electrodes = Rv/n 5- calculate the length of the horizantal plate using r= resistivity*sqrt(pi/A)/4

Earthing system the value of the earthing resistance:-
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system the value of the earthing resistance:- The fig shows the occuring of short circuit of one phase with ground in TT earthing system The short circuit current depends on the voltage and the resistances ro and re with addition to the resistance of the cables Assume ro=re=4 ohm Ie=220/8=27.5 A The voltage on the motor = 110 V If re=4 ohm and ro=1.5 ohm then the voltage will be (220x4)/5.5= 150 V which can kill the person

Earthing system the value of the earth resitance:-
An-Najah National University Faculty of Engineering Electrical Engineering Department Earthing system the value of the earth resitance:- The regulations states that the maximum voltage that should appears on the metal parts that are not carrying any currents in normal condition should not more than 42 V in fault condition V phase x re)/(rs+ro) <= 42 V re<= (42*ro)/ (V phase-42) ohm If V phase =220 then re <=0.236 ro. The earth resistance of the consumer should be 4 times less than the earth resistance of the supplier. The regulation states that the earth resistance of the consumer should be less than 4 ohms So re<= 0.236*4 = ohm Regulations states that the earth resistance of the consumer shouldn’t exceed 2 ohms

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system In general it is possible to obtain enough protection in the case of fault in one of the following ways:- 1- if the voltage appears on the metal part that are not carrying any current in normal condition is very small (less than 42 V) and this is done if the earth resistance is very small. 2- if the faukt current is very small and enough to make the protection device to work ( either the fuse or the CB)

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system The earthing system in electrical companies:- 1- earthing the distribution networks Every meduim voltage tower or pole (33 kv) is earthed through copper wire connecting with an electrode buried under the pole. The earth resistance should be less than 10 ohm. 2- the low voltage distribution newtworks (0.4 kv) is earthed through the poles in away that every pole from five or six poles is earthed thorugh electrode. The earthing in low voltage networks (0.4 V) follow the following earthing systems:- 1- earthing system (TN-S) :- the low voltage distribution netwrok consist of ( 3 phase , 1 N , 1 E) 2- earthing system (TN-C-S) :- 3 phase + 1N + 1 E

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system The earthing system in electrical companies:- 1- earthing the distribution networks Every meduim voltage tower or pole (33 kv) is earthed through copper wire connecting with an electrode buried under the pole. The earth resistance should be less than 10 ohm. 2- the low voltage distribution newtworks (0.4 kv) is earthed through the poles in away that every pole from five or six poles is earthed thorugh electrode. The earthing in low voltage networks (0.4 V) follow the following earthing systems:- 1- earthing system (TN-S) :- the low voltage distribution netwrok consist of ( 3 phase , 1 N , 1 E) 2- earthing system (TN-C-S) :- 3 phase + 1N + 1 E

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system The earthing system in electrical companies:- 1- earthing the distribution transformers:- the distribution transformer 33/0.4 kv is connected in delta from the high side and in star in the low voltage side The neutral is connected directly with the earth the distribution transformer 132/33 kv is connected in star in high voltage and the neutral is connected directly with the earth The low voltage is connected in delta

Earthing system An-Najah National University Faculty of Engineering
Electrical Engineering Department Earthing system The earthing system in electrical companies:- 4- earthing the main cables:- all the ends of the cables 11kv ,33 kv with three cores . The ends of the cable is connected with the earthing network to prevent voltage from appearing between the two ends of the cable in the faulty condition

Lightning protection An-Najah National University
Faculty of Engineering Electrical Engineering Department Lightning protection about 8 million light flashes occurs every day or 100 light flashes ever second about 18.2 % of the fires in buildings are due to the lightning phenomena

Lightning protection An-Najah National University
Faculty of Engineering Electrical Engineering Department Lightning protection the water vapour is condensed in the air and then water drops are formed These water drops are frozen due to the low temperature The temperature inside the water drop is higher than that at the surface the positive Ions is directed to the surface under the effect of the difference in the temperature and charged it with positive charge The inner side of the water drop is become charged with negative charge

Lightning protection An-Najah National University
Faculty of Engineering Electrical Engineering Department Lightning protection the electrical charges after the broken of the cover is trasfered to the top and so the the tope side of the cloude will be ositively charged and the lower side will be negatively charged. As the concentrate of the electrical charges is increased in the cloud , the voltage of electrical field of the cloud will increase When it reaches kv .cm which depend on the hieght of the cloud , the air will strat to be ionized and then the air become conducting .

Lightning protection An-Najah National University
Faculty of Engineering Electrical Engineering Department Lightning protection the electrical discharge is started when the cloude is started to send negative charges to the ground . These neagtive charges moving to the earth with avergae speed of m/s . When these charges moves 45m it stops. And start a new route. The time needed for this step is ms As much these charges become closer to the ground, the time will be reduced , and the current will be A

Lightning protection An-Najah National University
Faculty of Engineering Electrical Engineering Department Lightning protection the electrical discharge is started when the cloude is started to send negative charges to the ground . These neagtive charges moving to the earth with avergae speed of m/s . When these charges moves 45m it stops. And start a new route. The time needed for this step is ms As much these charges become closer to the ground, the time will be reduced , and the current will be A

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system it is important to save life and buildings from fires It is used to detect the fire and determine its source in the early stages Then it sends alarming signal in order to take safety procedures Alarming system goes in stages:- Detecting the fire (time is important) Response stage (determine the source of the fire and its place) Extinguishing stage

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system fire alarm consist of Control unit Fire detector Manual stations Power supply Supplementary equipment

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system detectors Smoking detector Heat detector Radiation detector

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system Manual stations : it is a unites through which the the alarming circuits is closed to give a manual alarm for a fire Bells and horns : it is units gives a specific sounds for alarming Control unit:- 1- it is consist of a digital and electronic circuits 2- it is receive the signal comes from the detector 3- send a signal to the bells and horns 4- it consists of lamps to show the zone in which the fire exist 5- there is switch in it that returns the alarm to the normal condition 6- it is supplied with electrical power from main power source and a standbb source 7- the main source come from the D.B with sperate circuit breaker and feeder 8- the standby power suppll consist of rechargable batteries or UPS

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system spacing of detectors It is important to determine the distance covered by the detector such as all the needed ares are covered bb the detectors The spacing of detectors rules:- 1- each detector covers area of 83 m2 2- the spacing between two detectors vertically and horizantally not more than 9m 3- the distance between any centre of fire and any detector not exceed 6.4 m

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system electrical installation of the fire alarm systems There are two types of alarm system installation 1- open circuit 2- closed circuit

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system open circuit In this type the alarm points ( detectors , manual station) is connected in parallel and its switch are normally opened . When a fire is occured, this switches is closed and start passing currents which gives a signal to the control unit and as a result the horns and bells start working.

Fire alarm system An-Najah National University Faculty of Engineering
Electrical Engineering Department Fire alarm system closed circuit In this type the alarm points ( detectors , manual station) is connected in series with the coil of the relay which is closed when no current is passing in it and open when is passing. The alarming points are closed in normal condition and there is a current passing in the relay coil so the breaker near the bells are open When there is a fire one of the alarming point become open circuit and so no current will bas in the oil of the relays and so the circuit breaker near the bells will be closed. It is more trustable than the previous method . Any fualt in the relay or any cutting in the wire will make the system alaring.

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches push button switch : ON:- it is used to pass the current to the coil when it is pressed OF :- it is used to open the circuit and so no current will pass in the coil

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Limit switch these switches have many auxiliary normally closed and normally open switches and the situation of these switches will change when any thing collapse with it It is used to conduct or cut the current from the coil when the load reaches a specific distance or height It is found in elevators There are special types of them called the photo electronic detector , and the auxiliary switches will be changed in it whenever something passes in front of it at a specific distance without need of mechanical touch.

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Pressure switch A pressure switch is a form of switch that makes electrical contact when a certain set pressure has been reached on its input. This is used to provide on/off switching from a pneumatic or hydraulic source. The switch may be designed to make contact either on pressure rise or on pressure fall. Pneumatic Uses of pneumatic pressure switches include: switching off an electrically driven gas compressor when a set pressure is achieved Switching off a gas compressor, whenever there is no feed. Hydraulic Hydraulic pressure switches have various uses in automobiles, for example: to switch on a warning light if engine oil pressure falls below a safe level to switch on brake lights automatically by detecting a rise in pressure in hydraulic brake pipes In dust control systems (bag filter), a pressure switch is mounted on the header which will raise an alarm when air pressure in the header is less than necessary to gain or decline energy beyond the set value

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Float switch:- it is used for controlling the rising or falling of the level of liquids The auxiliary switches state are changed when the level of a liquid is rising above or falling below a specific level.

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Timer :- it is used to conduct the current to the coil or cdisconnect it automatically after a specific time at which the time is adjusted.

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Power and control circuits any control unite in any machine has a motor or more is divided into 2 separate circuits, power circuit and contrpl circuit 1- power circuit:- it is the circuit used to conduct the current from source to the motor and consist of A- fuses or CB B– contactors(3) C-heat coils for overload (3) D-motor terminal E-wires All the components in this circuit should be able to carry the rated current of the motor used

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches 2- control circuit:- it used to conduct the current to the contactor coil and consist of:- A- Fuse or CB B- on and off switches Contactor auxiliary switches Normally closed auxiliary switches for the heat breaker All these components should carry current of the coil which is very small current

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches 2- control circuit:- it used to conduct the current to the contactor coil and consist of:- A- Fuse or CB B- on and off switches Contactor auxiliary switches Normally closed auxiliary switches for the heat breaker All these components should carry current of the coil which is very small current

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches 2- control circuit:- it used to conduct the current to the contactor coil and consist of:- A- Fuse or CB B- on and off switches Contactor auxiliary switches Normally closed auxiliary switches for the heat breaker All these components should carry current of the coil which is very small current

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Power electric circuit consist of:- 1- current sources L1,L2,L3 2- 3 fuses 3- 3 contacts points 4- 3 over load contacts 5- 3 motor terminals

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Control circuit 1- fuse 2- contacts point for overload coil On switch Off switch Coil The voltage across the control circuit equals the voltage that the coil can carry

Type of switches An-Najah National University Faculty of Engineering
Electrical Engineering Department Type of switches Control circuit Connecting the lamp units in the control circuit Rm over load lamp point LM light when the motor rotates LF over load disconnection

How to choose the terminals of control circuit
An-Najah National University Faculty of Engineering Electrical Engineering Department How to choose the terminals of control circuit the terminals of the control should have a voltage difference equals the rating voltage of the coil In some circuits , the rating voltage of the coil is the same of the voltages between the three phases And in this case , any two phases are used in control circuit In some circuits , the rating of the coil equals the volage between any phase an the neutral, and in this case any phase from the three phases is used in control circuit In many circuits , the rating voltage of the coil will be small , 24,48,110 V, and in this case , a transformer is used to obtain the desired voltage.

How to choose the terminals of control circuit
An-Najah National University Faculty of Engineering Electrical Engineering Department How to choose the terminals of control circuit example : control circuit to control a motor start and stop from two different places note:- in the case of switching on the same coil from different places , the start switching should be connected in parallel with an auxiliary open switch In the case of switching off the coil from different places, all the stop switches should be connected in series In the dangerous machines, the control circuit is designed in away that the machine will not work till a two switches are pressed simulatneously. And the two switches are spaced in away that the worker should use both of his hands to press the two switches

Power and control circuit for single phase motor
An-Najah National University Faculty of Engineering Electrical Engineering Department Power and control circuit for single phase motor the contactor and overload that are used in controlling a 3 phase motors can be used in controlling a single phase motor

Controlling the motor in opposite direction
An-Najah National University Faculty of Engineering Electrical Engineering Department Controlling the motor in opposite direction The change of direction of rotation of a 3 phase motor by changing the connection of the two phases from three . Note:- if the three phase are changed, then the direction of rotation will be in the same direction

Controlling the motor in opposite direction
An-Najah National University Faculty of Engineering Electrical Engineering Department Controlling the motor in opposite direction Power circuit :- when closing the contactor C1 , the electrical current will reach the motor in the sequence R S T……….. W U V When the closing the contactor C2 , the electrical current will reach the motor in the sequence R S T…………….W V U The electrical current in both cases will be the same

Star delta motor control
An-Najah National University Faculty of Engineering Electrical Engineering Department Star delta motor control The external connection of the motor can be either star or delta and in some cases the motor start with star connection and then change to be connected in delta connection There are two methods to connect the motor, and each method determine the voltage difference at which the motor will work

Star delta motor control
An-Najah National University Faculty of Engineering Electrical Engineering Department Star delta motor control The voltage difference in star connection is bigger than that in delta connection Vstar = sqrt(3) * V delta The current in star is less than that in delta I star= I delta/ sqrt(3) In the high power motor , it works at delta,. At the beginning of rotation it will be connected in star, then when it reaches the final speed it will change to delta The six terminals of the motor should be free The voltage difference of the source should be same with the voltage of the motor when it works in delta connection

Star delta motor control
An-Najah National University Faculty of Engineering Electrical Engineering Department Star delta motor control The voltage difference in star connection is bigger than that in delta connection Vstar = sqrt(3) * V delta The current in star is less than that in delta I star= I delta/ sqrt(3) In the high power motor , it works at delta,. At the beginning of rotation it will be connected in star, then when it reaches the final speed it will change to delta

Star delta motor control
An-Najah National University Faculty of Engineering Electrical Engineering Department Star delta motor control Power circuit:- C3 is used to connect the current to the terminal of the motor and it has a timer When the current passes coil 3 through the start button , the auxiliary switch C3 will be closed and the current will pass in coil 1. and the motor will be connected in star After some time, the timer will disconnect the current from C1 and connect it to coil 2 and the motor will work in delta

Timer An-Najah National University Faculty of Engineering
Electrical Engineering Department Timer It used in the cases that needed a start or stop of the motor after a specific time There are many types of them 1- the timer has a samll motor, when the current passes through it, it will start rotating gears and after a specific time, the gear will close a switch and open another switch When closing C , B lamp will light and after a specific time, B light will switch off and A lamp will light

Control circuit of 3 motors with timer
An-Najah National University Faculty of Engineering Electrical Engineering Department Control circuit of 3 motors with timer The circuit is used to start 3 motors , the first motor will start working using a start switch , after a specific time, the second swithc will start will start working and the first motor will stop, and after a specific time, the third motor will start working and the second motor will stop.

Series resistors An-Najah National University Faculty of Engineering
Electrical Engineering Department Series resistors In the motors with high power, another method used to protect the coils of the motors from high current at the start of start of rotation of the motor through connecting it with resistors in series

Series resistors An-Najah National University Faculty of Engineering
Electrical Engineering Department Series resistors At the beginning of rotation, a series of motors will be connected in series with the motor , then after a specific time the resistor will be switched off

Control circuit for main supply and auxiliary supply
An-Najah National University Faculty of Engineering Electrical Engineering Department Control circuit for main supply and auxiliary supply In some constructions , it is not allowed for the power supply to be switched off even for short time In such cases , the construction should have a mian power supply and a standby source In the case of switching of the power , the standby system will supply the constrcution with power Till the power returns back

Control circuit for main supply and auxiliary supply
An-Najah National University Faculty of Engineering Electrical Engineering Department Control circuit for main supply and auxiliary supply A: contactor for the main source R: auxiliary contactor with the main source T1: timer connected with the contactor A. this timer changes its contacts if a current passing hrough coil A and stays like that. And if the current stop passing in the coil A for a specific time its contacts return back to the normal situation B : contactor for the standby source

Control circuit for main supply and auxiliary supply
An-Najah National University Faculty of Engineering Electrical Engineering Department Control circuit for main supply and auxiliary supply If there is current in the main source , the current will pass through coil A and coil R and in this case the timer will colse its contacts but the current will not passs through coil B because the normally closed auxiliary switches A R will be opened. in the case of cutting of the source from the main , the normally closed auxiliary switches A and R will be changed to be closed and so the current will bas through coil b and the stand by source will be the source. When the current returns back in the main source, the current will pass through coil R and the switch will open . And so no current will pass through coil B, then the current will pass through coil A

Control circuit for motor with 2 speeds
An-Najah National University Faculty of Engineering Electrical Engineering Department Control circuit for motor with 2 speeds

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply UPS types Standby Line Interactive Standby-Ferro Double Conversion On-Line Delta Conversion On-Line

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Standby UPS The Standby UPS is the most common type used for Personal Computers

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Standby UPS the transfer switch is set to choose the filtered AC input as the primary power source (solid line path), and switches to the battery / inverter as the backup source should the primary source fail. When that happens, the transfer switch must operate to switch the load over to the battery / inverter backup power source (dashed path). The inverter only starts when the power fails, hence the name "Standby High efficiency, small size, and low cost are the main benefits of this design

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Line Interactive UPS is the most common design used for small business, Web, and departmental servers

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Line Interactive UPS In this design, the battery-to-AC power converter (inverter) is always connected to the output of the UPS. Operating the inverter in reverse during times when the input AC power is normal provides battery charging. When the input power fails, the transfer switch opens and the power flows from the battery to the UPS output. With the inverter always on and connected to the output, this design provides additional filtering and yields reduced switching transients when compared with the Standby UPS topology. In addition, the Line Interactive design usually incorporates a tap-changing transformer. This adds voltage regulation by adjusting transformer taps as the input voltage varies. High efficiency, small size, low cost and high reliability coupled with the ability to correct low or high line voltage conditions make this the dominant type of UPS in the 0.5-5kVA power range.

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Standby-Ferro UPS The Standby-Ferro UPS was once the dominant form of UPS in the 3-15kVA range.

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Line Interactive UPS This design depends on a special saturating transformer that has three windings (power connections). The primary power path is from AC input, through a transfer switch, through the transformer, and to the output. In the case of a power failure, the transfer switch is opened, and the inverter picks up the output load. In the Standby-Ferro design, the inverter is in the standby mode, and is energized when the input power fails and the transfer switch is opened. The transformer has a special "Ferro-resonant" capability, which provides limited voltage regulation and output waveform "shaping". The isolation from AC power transients provided by the Ferro transformer is as good as or better than any filter available. But the Ferro transformer itself creates severe output voltage distortion and transients, which can be worse than a poor AC connection. Even though it is a standby U PS by design, the Standby-Ferro generates a great deal of heat because theFerro-resonant transformer is inherently inefficient. These transformers are also large relative to regular isolation transformers; so standby-Ferro UPS are generally quite large and heavy.In addition, the Line Interactive design usually incorporates a tap-changing transformer. This adds voltage regulation by adjusting transformer taps as the input voltage varies.

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Double Conversion On-Line UPS This is the most common type of UPS above 10kVA

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Line Interactive UPS is the same as the Standby, except that the primary power path is the inverter instead of the AC main. In the Double Conversion On-Line design, failure of the input AC does not cause activation of the transfer switch, because the input AC is charging the backup battery source which provides power to the output inverter. Therefore, during an input AC power failure, on-line operation results in no transfer time.

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Delta Conversion On-Line UPS 10 year old technology introduced to eliminate the drawbacks of the Double Conversion On-Line design and is available in sizes ranging from 5kVA to 1.6MW.

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply The Line Interactive UPS Similar to the Double Conversion On-Line design, the Delta Conversion On-Line UPS always has the inverter supplying the load voltage the additional Delta Converter also contributes power to the inverter output. Under conditions of AC failure or disturbances, this design exhibits behavior identical to the Double Conversion On-Line.

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Summary of UPS types

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply

UPS Un interruptible power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptible power supply Use of UPS types in the industry

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Use of UPS types in the industry Ultracapacitors have distinct advantages including: > storing high quantities of energy > accepting many charge/discharge cycles without suffering any wear > acceptable service life > satisfactory operation over wide temperatures range > For high power ratings and backup times of ≥several seconds required by UPSs, cost is high – ≈€10,000 for 50 kW Useful primarily for peak load shaving due to very fast charge/discharge cycle Relatively small in size, and are a promising technology for UPS applications Used to supply extra power (e.g. improve performance of electrical vehicles) or supply lowc urrent, long-duration loads (e.g. computer memory backup applications).).

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Use of UPS types in the industry

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Flywheels – Low speed Operation: > "no-break" system, metal flywheel connected to genset motor & generator > AC-input is available : machine operates in motor mode as a synchronous conditioner > AC-input unavailable : synchronous machine operates as AC generator using flywheels kinetic energy to supply output voltage. > Regulation system maintains output voltage in spite of drop in flywheel speed. Advantages include: > Long backup times when used with engine generator set > Rotating at a relatively low speed (≈1,500 rpm); makes it possible to use standard bearings Challenges: > Requires regular and costly maintenance with system shutdown > “Environmental costs ?” > Low efficiency, uses <5% of the stored kinetic energy > Systems as a whole are large & noisy

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Flywheels – Low speed Operation: > Compact systems with high energy density thanks to new lightweight composite materials & electronics developments > Currently being paired with UPSs for special applications. > High speeds : 30,000 to 100,000 rpm – kinetic energy proportional to the square of rotating speed > Motor-driven rotor maintained by magnetic bearings in a levitating position in a vacuum Advantages: > compact size > excellent efficiency > low noise levels Disadvantages: > risks due to structural faults in the rotor > Very high cost of the materials > “Environmental costs ?”

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Flywheels – Low speed Operation: > Compact systems with high energy density thanks to new lightweight composite materials & electronics developments > Currently being paired with UPSs for special applications. > High speeds : 30,000 to 100,000 rpm – kinetic energy proportional to the square of rotating speed > Motor-driven rotor maintained by magnetic bearings in a levitating position in a vacuum Advantages: > compact size > excellent efficiency > low noise levels Disadvantages: > risks due to structural faults in the rotor > Very high cost of the materials > “Environmental costs ?”

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size 1- Make a list of the equipment that needs protection. Include all individual items that have their own power cords, such as CPU, monitor, modem, etc 2. Obtain the wattage rating of each device 3 Add the total wattage ratings for all devices to be protected 4-Determine the maximum back-up time needed to shut down critical equipment only, should an outage occur

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply How to determine the correct UPS size

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Under normal operating conditions (i.e. when the mains voltage is within the accepted range), the synchronous motor draws a compensating current so as to maintain a constant load voltage level. Also during normal operation, kinetic energy is stored in the flywheel (or induction coupling) When the mains fail, the stored flywheel energy is extracted to support the load. Flywheel inertia (or induction coupling speed range) is sized to support the full load operation for a specific period (typically a few seconds), during which time the backup diesel generators are started.

Passive standby An-Najah National University Faculty of Engineering
Electrical Engineering Department Passive standby

UPS Un interruptable power supply
An-Najah National University Faculty of Engineering Electrical Engineering Department UPS Un interruptable power supply Passive Stand-By In this topology, the system monitoring and control unit continuously monitors the utility voltage and frequency to determine if they are within the specified limits. If the utility source parameters are within +/-10%, the load is directly fed from the utility mains through the fast acting static switch. During this condition (standby mode) the power inverter remains energized but does not supply any power to the load. The battery charger maintains the voltage level of the batteries during this time. In the event of any power failure at the mains or if the mains power parameters go out of the specified limit, the system control turns off the fast acting static switch and turns on the inverter. Under this condition (Stored energy mode) the inverter supplies the load power by converting energy from the battery.

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