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Electrical Machines

Electrical Machines. LSEGG216A 9080V. Transformer Operation. Week 4 . Transformer Operation. CIVIL. V+. Voltage. Current. Magnetic Flux. Transformer Operation. Applied Voltage. Induced Voltage. V’ 2. V’ 1. V 1. Induced Voltage in Secondary. I M. Resultant Current.

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Electrical Machines

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  1. Electrical Machines LSEGG216A 9080V

  2. Transformer Operation Week 4

  3. Transformer Operation CIVIL V+ Voltage Current Magnetic Flux

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

  5. 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

  6. Transformer Operation Ie V1 Ie= Iron loss current Io = No load current Io IM

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

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

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

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

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

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

  13. Transformation Ratio V1x I1 K = 2 200V 100V V2 x I2 400 200

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

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

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

  17. Voltage Regulation 100 x VNo Load – V Full Load R% = VFull Load If PF = Unity 100 x I x (R x cos + XL x sin) R% = VFull Load

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

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

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