7/08/2002PP.AFD.07 Harmonic Quality1 of 49 Yaskawa Electric America Harmonic Currents, Voltages and Your Building Power System

7/08/2002PP.AFD.07 Harmonic Quality2 of 49 Discussion Points n Power Factor n Harmonics n The Building Power System n Current Distribution Limits n Power System Solutions

7/08/2002PP.AFD.07 Harmonic Quality3 of 49 Power Factor n Power Factor is the ratio of the actual power (kW) being used to the apparent power being drawn from the line (kVA) n Measurement of the effectiveness of power usage The higher the PF, the more efficient the system The higher the PF, the more efficient the system

7/08/2002PP.AFD.07 Harmonic Quality4 of 49 Power Factor  To determine Power Factor, divide kW by apparent power (kVA)  Low Power Factor increases cost of supplying power Overloads generators, transformers, distribution lines, etc. Utilities penalize large users for low power factor kVA kW kVAR Power Factor = kW / kVA kVAR is reactive power - Maintains the electromagnetic field

7/08/2002PP.AFD.07 Harmonic Quality5 of 49 Power Factor AC Drives power factor follows concept except current not a pure sinewave, they contain harmonics Current closer to a square wave than sine wave Most VFD manufacturers use displacement power factor Displacement PF = The cosine of the angle between the fundamental kVA and kW

7/08/2002PP.AFD.07 Harmonic Quality6 of 49 Power Factor T he effect of harmonics reduces true power factorT he effect of harmonics reduces true power factor Power factor measurement by utilities only measure fundamental current, therefore only measure displacement PF.Power factor measurement by utilities only measure fundamental current, therefore only measure displacement PF. kW kVA kVA ( Harmonic) kVAR Harmonic kVAR

7/08/2002PP.AFD.07 Harmonic Quality7 of 49 Power Factor PF % SPEED.95 FIG 1FIG 2 Fig 1. Six step VFD Power Factor Linear with speed Fig 2. PWM VFD PF constant with speed Harmonics reduce PF for both but can be improved using DC Link Reactors, AC Line Reactors, etc 100%

7/08/2002PP.AFD.07 Harmonic Quality8 of 49 Power Factor Summary n The higher the PF, the more efficient the system n Harmonics may result in reduction in power factor n All non-linear loads add to harmonics n Utilities may penalize for low power factor n Utilities measure displacement PF. n Bottom Line: Not being penalized? No Problem!

7/08/2002PP.AFD.07 Harmonic Quality9 of 49 Harmonics: What Are They? n Fundamental - the Base Frequency For Power Lines 60 Hz is Fundamental For Power Lines 60 Hz is Fundamental n Harmonic - Multiples of the Fundamental Fifth Harmonic is (5 x 60) or 300 Hz Fifth Harmonic is (5 x 60) or 300 Hz n Only Associated With Periodic Waveforms

7/08/2002PP.AFD.07 Harmonic Quality10 of 49 Harmonics: What Are They? IEEE 519 defines harmonics as: A sinusoidal component of a periodic waveform or quantity having a frequency that is a multiple of the fundamental frequency A sinusoidal component of a periodic waveform or quantity having a frequency that is a multiple of the fundamental frequency They are steady state state distortion of the AC line, unlike transients, surges and other things that typically only last a few cycles. They cause stress in the distribution system and can cause heating of motors and transformers They are steady state state distortion of the AC line, unlike transients, surges and other things that typically only last a few cycles. They cause stress in the distribution system and can cause heating of motors and transformers Reduces the operational life of these devices Reduces the operational life of these devices

7/08/2002PP.AFD.07 Harmonic Quality11 of 49 Harmonics: What are they? n Harmonics can also affect the power supplies of other VFDs n Can cause spurious fuse blowing and circuit breaker trips

7/08/2002PP.AFD.07 Harmonic Quality12 of 49 Harmonic Waveforms

7/08/2002PP.AFD.07 Harmonic Quality13 of 49 Calculating Harmonic Distortion n Harmonic and Fundamental Currents Not Added Directly Not Added Directly “Square Root of Sum of Squares” “Square Root of Sum of Squares” Total Harmonic Distortion (THD) =  ( I I I I I )) / I fund Total Harmonic Distortion (THD) =  ( I I I I I )) / I fund Total Current =  I fund 2 + I harm 2 ) Total Current =  I fund 2 + I harm 2 )

7/08/2002PP.AFD.07 Harmonic Quality14 of 49 Harmonic Current and THD System Voltage v System Voltage v Load 1 - A Personal Computer Power Supply Load 1 - A Personal Computer Power Supply Load hp HVAC Air Handler Motor Load hp HVAC Air Handler Motor I harm = I fund * THD (in %) *.01 I harm = I fund * THD (in %) *.01 I fund = Watts / Volts I fund = Watts / Volts I tot =  I fund 2 + I harm 2 ) I tot =  I fund 2 + I harm 2 )

7/08/2002PP.AFD.07 Harmonic Quality15 of 49 Building Power System n Building Loads Repetitive and Synchronous Repetitive and Synchronous Random and Asynchronous Random and Asynchronous n Distribution System Service Entrance/Distribution Transformers Service Entrance/Distribution Transformers The Bus/ Riser System The Bus/ Riser System The Power/Lighting Distribution Panels The Power/Lighting Distribution Panels Circuit Breakers Circuit Breakers

7/08/2002PP.AFD.07 Harmonic Quality16 of 49 Building Load Types n Repetitive and Synchronous Resistive Resistive Reactive Reactive Nonlinear Nonlinear n Random and Asynchronous Transients Transients Noise Noise

7/08/2002PP.AFD.07 Harmonic Quality17 of 49 Resistive Loads n Examples of Resistive Loads Incandescent Lighting Incandescent Lighting Electric Heater Elements Electric Heater Elements n Resistive Load Current I load = V load / R load I load = V load / R load I Waveform Proportional to V Waveform I Waveform Proportional to V Waveform

7/08/2002PP.AFD.07 Harmonic Quality18 of 49 Resistive Waveshapes

7/08/2002PP.AFD.07 Harmonic Quality19 of 49 Reactive Load n Examples of Reactive Loads Electric Motors Electric Motors Contactors, Relays, Solenoids Contactors, Relays, Solenoids Transformers, Line Reactors Transformers, Line Reactors n Reactive Load Current I load = V load /  (R 2 load + L 2 load ) I load = V load /  (R 2 load + L 2 load ) Current Phase Shifted with respect to Voltage Current Phase Shifted with respect to Voltage I Waveform Proportional to V Waveform I Waveform Proportional to V Waveform

7/08/2002PP.AFD.07 Harmonic Quality20 of 49 Reactive Waveshapes

7/08/2002PP.AFD.07 Harmonic Quality21 of 49 Non-Linear Loads n Examples of Non-Linear Loads Computers, Faxes, Printers, Phone Systems Computers, Faxes, Printers, Phone Systems Variable Frequency Drives (VFDs) Variable Frequency Drives (VFDs) n Non-Linear Load Current (Single Phase) I load = (sin 1f) + (sin 3f) *n 3 + (sin 5f) *n 5 + (sin 7f) *n 7 + (sin 9f) *n 9 + (sin 11f) *n I load = (sin 1f) + (sin 3f) *n 3 + (sin 5f) *n 5 + (sin 7f) *n 7 + (sin 9f) *n 9 + (sin 11f) *n I load Characteristics I load Characteristics – Zero for 120 Degrees of Half Cycle – High Crest Factor Surge for 30 Degrees

7/08/2002PP.AFD.07 Harmonic Quality22 of 49 Non-Linear Waveshapes

7/08/2002PP.AFD.07 Harmonic Quality23 of 49 Non-Linears Rich in Harmonics

7/08/2002PP.AFD.07 Harmonic Quality24 of 49 3 Phase Rectifier Current Three Phase Harmonic Spectrum Harmonic Number %ofFundamental

7/08/2002PP.AFD.07 Harmonic Quality25 of 49 Transient Load Characteristics n Examples of Transient Loads (at turn-on/turn-off) Elevator Motors Elevator Motors A/C Compressor Motors A/C Compressor Motors Short Circuit / Breaker Clear Short Circuit / Breaker Clear n Transient Load Current I transient Is Unpredictable and Asynchronous I transient Is Unpredictable and Asynchronous I transient Approximates a Step Response I transient Approximates a Step Response

7/08/2002PP.AFD.07 Harmonic Quality26 of 49 Transient Waveshapes

7/08/2002PP.AFD.07 Harmonic Quality27 of 49 Noise Characteristics n Example of Noise VFD Power Converter Switch Spikes VFD Power Converter Switch Spikes Relay Openings and Closures Relay Openings and Closures n Noise Currents I noise Large and of Short Duration (uSec) I noise Large and of Short Duration (uSec) I noise May be Common or Differential Mode I noise May be Common or Differential Mode

7/08/2002PP.AFD.07 Harmonic Quality28 of 49 IEEE Table 10-3 Isc/ IL Harmonic Current (Odd) < >1000 <1111<h<1717<h<3535<h % THD IEEE Table 10-3 Recommended Practice Max Harmonic Current Distortion of the Fundamental

7/08/2002PP.AFD.07 Harmonic Quality29 of 49 Current Distortion Limits n PCC (Point of Common Coupling) Most important and most controversial item in IEEE Most important and most controversial item in IEEE Defined as: Defined as: – The electrical connecting point between the utility distribution system and the users electrical distribution system n (I SC ) Max Short Circuit Current at PCC – Determined by the size, impedance, and voltage of the service feeding the PCC.

7/08/2002PP.AFD.07 Harmonic Quality30 of 49 IEEE 519 n (I L ) Max demand load current at PCC – Facilities should measure this over a period of time and average it. – If not possible - calculate the anticipated peak operation of the facility n (I SC /I L )The ratio of available current at the PCC to the max demand load current at the same point. – Measures the stiffness of the electrical system relative to the load. The larger the power source in relationship to the load, the stiffer the system.

7/08/2002PP.AFD.07 Harmonic Quality31 of 49 IEEE 519 n TDD - Total Demand Distortion – The measure of the total harmonic current distortion at the PCC for the total connected load. n PCC 1 as measuring point – TDD allowed to be 12% – 5th and 7th 15% – No filtering needed n PCC 2 as measuring point – TDD allowed to be 5% – 5th and 7th 4% – Filtering needed

7/08/2002PP.AFD.07 Harmonic Quality32 of 49 IEEE 519 VFD 69KV 13,800V PCC1 PCC2 480V PRIMARY OF SERVICE TRANSFORMER PCC1 - if THE COMPANY OWNS THE XFORMER, UTILITY WILL MEASURE HERE PCC2- IF UTILITY MEASURES 480V PCC 2 IS INTERFACE 20,000 KVA TR-1 8.5% 200kVA

7/08/2002PP.AFD.07 Harmonic Quality33 of 49 IEEE 519 n Voltage Distortion Limits per IEEE 519 n Defines the quality of power on the electrical distribution system. – Individual Voltage Distortion 3% – Total Voltage Distortion 5% allowed

7/08/2002PP.AFD.07 Harmonic Quality34 of 49 Harmonic Solutions n No Filtering Loads less than 25%- must be very stiff Loads less than 25%- must be very stiff n Isolation Transformers Very costly Very costly Not required by PWM drives except as harmonic filters Not required by PWM drives except as harmonic filters

7/08/2002PP.AFD.07 Harmonic Quality35 of 49 Harmonic Solutions n AC Line Reactors - 25% Load Greatly improves voltage distortion Greatly improves voltage distortion Current distortion improvement similar to DC Link Reactor Current distortion improvement similar to DC Link Reactor More cost effective than Isolation Transformer More cost effective than Isolation Transformer Usually effective means of meeting IEEE requirements Usually effective means of meeting IEEE requirements Improves power factor Improves power factor Protects VFDs from transients Protects VFDs from transients

7/08/2002PP.AFD.07 Harmonic Quality36 of 49 Harmonic Solutions n DC Link Reactor up to 40% Load More cost effective than AC Line Reactor More cost effective than AC Line Reactor Reduces Voltage Distortion effectively Reduces Voltage Distortion effectively Reduces Current Distortion somewhat less effectively Reduces Current Distortion somewhat less effectively Improves PF but not as well as AC Reactor Improves PF but not as well as AC Reactor Smaller than AC Reactors Smaller than AC Reactors n DC Link w/ AC Line Reactor Somewhat better than either system alone Somewhat better than either system alone Similar results as DC Link Reactor Similar results as DC Link Reactor

7/08/2002PP.AFD.07 Harmonic Quality37 of 49 Harmonic Solutions n Harmonic Trap Filter - 60% Loaded 5th Harmonic Trap Filter in series with AC 5% Line Reactor 5th Harmonic Trap Filter in series with AC 5% Line Reactor Effective at reducing Voltage and Current distortion Effective at reducing Voltage and Current distortion Very expensive Very expensive

7/08/2002PP.AFD.07 Harmonic Quality38 of 49 Harmonic Solutions n 12 Pulse (Dual Diode) Transformer 80% or more Most effective method of Harmonic Distortion reduction Most effective method of Harmonic Distortion reduction Not as expensive as Trap Filters Not as expensive as Trap Filters Similar in size to Isolation Transformers Similar in size to Isolation Transformers Last resort Last resort

7/08/2002PP.AFD.07 Harmonic Quality39 of 49 Harmonics Conclusions n All non-linear power structures cause harmonics n Harmonics reduce power factor n Filtering requirements depend on where you are measuring harmonics n Knowing all harmonic distortion and using appropriate filtering on a system wide approach, insures a more reliable, cost effective solution.

7/08/2002PP.AFD.07 Harmonic Quality40 of 49 Typical Harmonic Contents

7/08/2002PP.AFD.07 Harmonic Quality41 of 49 Distribution System n Service Entrance Transformers n Power Distribution Transformers n Lighting Distribution Transformers n “Isolation” Transformers n The Building Riser System n Power/Lighting Panels, Circuit Breakers

7/08/2002PP.AFD.07 Harmonic Quality42 of 49 All Transformers Are Inductive

7/08/2002PP.AFD.07 Harmonic Quality43 of 49 Transformer Impedance vs. Hz

7/08/2002PP.AFD.07 Harmonic Quality44 of 49 V distort Increases With Frequency Z xfmr = 2  * freq * L xfmr Z xfmr = 2  * freq * L xfmr n V drop = I harm * Z xfmr

7/08/2002PP.AFD.07 Harmonic Quality45 of 49 Current Is Problem, Not THD n Assume all 5th Harmonic Current n Use 1.35 ohm Transformer Z n V drop = I harm * Z xfmr

7/08/2002PP.AFD.07 Harmonic Quality46 of 49 Result: Voltage Distortion

7/08/2002PP.AFD.07 Harmonic Quality47 of 49 Summary: Harmonic Current n Total Harmonic Distortion - THD Causes Nothing Causes Nothing It Is a Factor, a Percentage It Is a Factor, a Percentage n Harmonic Current Can be a Problem A Function of Total Current A Function of Total Current And Total Harmonic Distortion (THD) And Total Harmonic Distortion (THD) n I harmonic Current Can Cause Voltage n Modern Loads on the Power Bus Produce High Harmonic Current Produce High Harmonic Current Cause Spikes, Transients, Noise Cause Spikes, Transients, Noise

7/08/2002PP.AFD.07 Harmonic Quality48 of 49 Summary: Distribution n The Power System - Inductive in Nature n Impedance Increases With Frequency n The Bus Distributes to Other Loads: Distorted System Voltage Distorted System Voltage Voltage Dropouts Voltage Dropouts Voltage Spikes, Surges, Transients Voltage Spikes, Surges, Transients System Resonances System Resonances

7/08/2002PP.AFD.07 Harmonic Quality49 of 49 Conclusions for the Industry n Retrofits Reduce Total Building Current n Harmonics - No Problem w/Lighting Circuit Loads are Typically Balanced Loads are Typically Balanced Ballasts Have Low Harmonic Current Ballasts Have Low Harmonic Current Electronic Ballasts Reduce Harmonic Current Electronic Ballasts Reduce Harmonic Current n Harmonics - Problem with Power Panels Loads may be Unbalanced Loads may be Unbalanced Loads Produce High Harmonic Current Loads Produce High Harmonic Current Loads are Susceptable to Distorted Voltage Loads are Susceptable to Distorted Voltage