1. HASMUKH GOSWAMI COLLEGE OF ENGINEERING
TOPIC :- Transformer
PREPARED BY, Guided by,
Radadiya Radhika L Niketan Dobriya
Champaneri Shubham R
Patel Jaimin S
Shrimali Chirag J
Tripathi Aman N
Electrical DEPARTMENT

2. Transformers A transformer is a device for increasing or decreasing
an a.c. voltage.

3. WHAT IS A TRANSFORMER?
TRANSFORMER IS A STATIC DEVICE WHICH TRANSFORMS A.C. ELECTRICAL POWER FROM ONE VOLTAGE TO ANOTHER VOLTAGE KEEPING THE FREQUENCY SAME BY ELECTROMAGNETIC INDUCTION.

4. TYPES OF TRANSFORMER BY APPLICATION
1. DISTRIBUTION TRANSFORMER
2.POWER TRANSFORMER
3.CURRENT TRANSFORMER
4.POTENTIAL TRANSFORMER
5.FURNACE TRANSFORMER
6.BOOSTER TRANSFORMER
7.RECTIFIER TRANSFORMER
8.LOCOMOTIVE TRANSFORMER
9.MINING TRANSFORMER
10.PHASE SHIFTING TRANSFORMER
11.WELDING TRANSFORMER
12.HIGH VOLTAGE TESTING/SC TESTING TRF.
13.GROUNDING TRANSFORMERS
14.CONVERTER TRANSFORMER

5. Structure of Transformer

6. PARTS OF TRANSFORMER MAIN TANK RADIATORS CONSERVATOR EXPLOSION VENT
LIFTING LUGS
AIR RELEASE PLUG
OIL LEVEL INDICATOR
TAP CHANGER
WHEELS
HV/LV BUSHINGS
FILTER VALVES
OIL FILLING PLUG
DRAIN PLUG
CABLE BOX

7. Circuit Symbol for Transformer

8. How Transformer works Laminated soft iron core Output voltage (a.c.)
Input voltage
(a.c.)
Primary coil
Secondary coil

9. Laminated iron core – this links the two coils magnetically.
All transformers have three parts:
Primary coil – the incoming voltage Vp (voltage across primary coil) is connected across this coil.
Secondary coil – this provides the output voltage Vs (voltage across the secondary coil) to the external circuit.
Laminated iron core – this links the two coils magnetically.
Notice that there is no electrical connection between the two coils, which are constructed using insulated wire.

10. Two Types of Transformer
A step-up transformer increases the voltage - there are more turns on the secondary than on the primary.
A step-down transformer decreases the voltage - there are fewer turns on the secondary than on the primary.
To step up the voltage by a factor of 10, there must be 10 times as many turns on the secondary coil as on the primary. The turns ratio tells us the factor by which the voltage will be changed.

11. Formula for Transformer
Where Vp = primary voltage
Vs = secondary voltage
Np= Number of turns in primary coil
Ns = Number of turns in a secondary coil.

12. Ideal Transformer Relationships
Note that I2 and I2’
are in opposite directions

13. Worked example No. 1 The diagram shows a transformer
Worked example No. 1 The diagram shows a transformer. Calculate the voltage across the secondary coil of this transformer.
Step-up transformer!

14. Solution

15. Worked example No. 2 A transformer which has 1380 turns in its primary coil is to be used to convert the mains voltage of 230 V to operate a 6 V bulb. How many turns should the secondary coil of this transformer have?
VP = 230 V
NP = 1380
VS = 6 V
NS = ?
Obviously, a Step-down transformer!!

16. Solution

17. MAIN FEATURES OUTDOOR,OIL COOLED, 3 PHASE,50HZ
PRIMARY IS DELTA CONNECTED AND SECONDARY IS STAR CONNECTED.
NATURALY COOLED (ONAN TYPE).
AMONGST ALL THE TYPES OF TRANSFORMERS THIS IS THE MOST REQUIRED AND MOST USED TYPE.

18. MAINTENANCE OF TRANSFORMER
Transformer is the heart of any power system. Hence preventive maintenance is always cost effective and time saving. Any failure to the transformer can extremely affect the whole functioning of the organization.

19. PROTECTION OF TRANSFORMERS
The best way of protecting a transformer is to have good preventive maintenance schedule.
Oil Temperature Indicators.
Winding Temperature indicators.
Buchholz Relay.
Magnetic Oil level Gauge.
Explosion Vent.

20. Transformer Losses and Efficiency
Core/Iron Loss =V12 / Rc1
Copper Loss = I12 R1+ I22 R2
Definition of % efficiency
= load power factor
Transformer

21. Maximum Transformer Efficiency
The efficiency varies as with respect to 2 independent quantities
namely, current and power factor
Thus at any particular power factor, the efficiency is maximum if
core loss = copper loss .This can be obtained by differentiating the
expression of efficiency with respect to I2 assuming power factor, and
all the voltages constant.
At any particular I2 maximum efficiency happens at unity power factor.
This can be obtained by differentiating the expression of efficiency
with respect to power factor, and assuming I2 and all the voltages
constant.
Maximum efficiency happens when both these conditions are satisfied.
Transformer

22. Maximum efficiency point
100
pf=1
pf= 0.8
pf= 0.6 
At this load current
core loss = copper loss
% full load current
Transformer

23. Thank you