1. Electrical Machines LSEGG216A 9080V

2. Transformer Operation Week 4

3. Transformer Operation V+ CIVIL VoltageCurrent Magnetic Flux

4. Transformer Operation Applied Voltage Induced Voltage Induced Voltage in Secondary Resultant Current V1V1 V’ 1 V’ 2 IMIM

5. Induced Voltage Φ max =Maximum instantaneous flux F = Frequency N = Number of turns B max = Maximum permissible flux density in Wb A = CSA of core in m 2

6. Transformer Operation V1V1 IMIM IeIe IoIo I e = Iron loss current I o = No load current

7. V1V1 V’ 1 V’ 2 IoIo I’ 2 I’ 1 I1I1

8. Transformer Operation V1V1 V’ 1 V’ 2 IoIo I’ 2 I’ 1 I1I1

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

10. V1=V1=N1N1 N2N2 V2=V2= = k = Transformation Ratio

11. Transformation Ratio V 1 x I 1 N1N1 N2N2 =V 2 x I 2 = I1I1 I2I2

12. Transformation Ratio V 1 x I 1 VA V 2 x I 2 kVA Power InPower Out

13. Transformation Ratio V 1 x I 1 V 2 x I 2 200  200V100V 400  K = 2

14. Voltage Regulation E I Voltage Drop Due to R Voltage Drop Due to X L V Resistance Inductance Coils have both

15. Voltage Regulation E I V Lagging PF of 45  V less than E

16. E I V Leading PF of 45  V More than than E

17. 100 x V No Load – V Full Load V Full Load R% = If PF = Unity 100 x I x (R x cos  + X L x sin  ) V Full Load R% =

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

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

20. Wattmeter reading V1V1 IMIM IoIo IeIe Supply Voltage Ammeter reading

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