1. Electrical Machines
LSEGG216A
9080V

2. Transformer Operation
Week 2

3. Introduction Basic operation AS/NZS symbols
Types Step-up, Step-down, Isolation

4. Transformer Operation
CIVIL V+
Voltage
Current
Magnetic Flux

5. Transformer Operation
Induced Voltage
V’2
V’1 V1
Induced Voltage in Secondary
Applied Voltage IM
Resultant Current

6. Induced Voltage Φmax =Maximum instantaneous flux F = Frequency
N = Number of turns
Bmax = Maximum permissible flux density in Wb
A = CSA of core in m2

7. Transformer OperationIe V1
Ie= Iron loss current
Io = No load current Io IM

8. Transformer Operation
V’2
V’1 V1
I’1 Io I1

9. Transformer Operation
V’2
V’1 V1
I’2
I’1 Io I1

10. Therefore the voltage can be varied by changing the number of turns
Transformation Ratio
Magnetic flux is common coils
Therefore the voltage can be varied by changing the number of turns

11. Transformation Ratio
V1= N1
= k
= Transformation Ratio
V2= N2

12. Transformation Ratio
V1x I1 =
V2 x I2 N1 I2 = N2 I1

13. Transformation Ratio
kVA VA
Power In
Power Out
V2 x I2
V1x I1

14. Transformation Ratio
K = 2
200V
100V
V2 x I2
V1x I1
800
200

15. Transformer Basic Tests
Open Circuit Test
Short Circuit Test
Oil Tests
Electrical Insulation
Polarity
Continuity

16. Open Circuit Test
Used to determine Iron Losses
Supply = Rated Voltage

17. Open Circuit Test Ie V1 Wattmeter reading Supply Voltage
Ammeter reading Io IM

18. Supply Adjusted = Rated Secondary Current
Short Circuit Test
Used to determine Copper Losses
Supply Adjusted = Rated Secondary Current