Electrical Machines (Transformer)

1.         The short circuit test on a transformer is conducted to obtain
A. copper losses.
B. core loses only.
C. eddy current loss
D. hysteresis loss
                                   
2.         In a transformer short circuit test and open circuit test are conducted
A. in LV side of transformer
B. in HV side and LV side of transformer respectively
C. in LV side and HV side of transformer respectively
D. in HV side of transformer
                                   
3.         In one 132/33KV transformer the LV resistance is 0.02 per unit. The resistance referred to HV side is
A.        0.08 pu
B.         0.02 pu
C.        0.16 pu
D.        0.01 pu
                                   
4.         Lamination of transformer core is made of
A.        cast iron.
B.         silicon steel.
C.        wrought iron.
D.        cast steel.
                                   
5.         Oil is provided in an Oil filled transformer
A.        both cooling and insulation
B.         insulating
C.        lubrication
D.        cooling
                                   
6.         Air core transformer as compared to iron core transformer, has
A.        more copper loss
B.         less magnetic core loss
C.        more magnetic core loss
D.        no magnetic core loss.
                                   
7.         CRGO Steel is used in the core of transformer to reduce
A.        Eddy Current loss
B.         Ohmic loss
C.        both Eddy Current and Hysteresis loss
D.        Hysteresis loss
                                   
8.         If input of a transformer is square wave the output will be
A.        puled wave.
B.         square wave.
C.        triangular wave.
D.        sine wave.
                                   
9.         Two transformers with identical rating, are designed with flux densities of 1.2 and 1.4 Wb/m2 respectively. The weight of first transformer per KVA is
A.        less than that of second transformer
B.         equal to that of second transformer
C.        more than that of second transformer
D.        None of these
                                   
10.       The flux involved in the emf equation of a transformer has
A.        r.m.s value
B.         maximum value.
C.        average value
D.        total value
                                   
11.       The no load current in a transformer lags the applied voltage by
A.        About 750
B.         00
C.        900
D.        About 1150
                                   
12.       The leakage flux in a transformer depends upon
A.        the applied voltage
B.         the load current
C.        the frequency
D.        the mutual flux.
                                   
13.       For satisfactory parallel operation of two transformers which of the following conditions is most essential,
A.        Polarities of all transformer operated in parallel must be connected properly.
B.         Percentage impedance of all transformers operated in parallel must be same.
C.        Voltage ratio of all transformer operated in parallel must be same.
D.        MVA rating of all transformer operated in parallel must be same.
                                   
14.       If a transformer has turns ration K, the primary and secondary current are I1 and I2 respectively and magnetizing current and core loss component of no load current Im and Iw respectively, then
A.        I1 = K.I2 + Iw
B.         I1 = K.I2 + Iw + Im
C.        I1 = K.I2 + Im
D.        I1 = K.I2
                                   
15.       Which of the following transformer insulating oil generally used in India
A.        paraffin based insulating oil
B.         naphtha based insulating oil
C.        aromatics based insulating oil
D.        olefin based insulating oil
                                   
16.       Winding conductors of an electrical power transformer are mainly insulated by
A.        Cotton Insulation.
B.         Rubber Insulation.
C.        Paper Insulation.
D.        Wooden Insulation

Answers
  1. a
  2. b
  3. b
  4. b
  5. a
  6. d
  7. d
  8. a
  9. c
  10. b
  11. a
  12. b
  13. a
  14. b
  15. a
  16. c          

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