Saturday, August 17, 2013

Transformers Objective Questions: Part-9

Transformers Objective Questions with Answers:

[1] High frequency transformers sometimes make use of ferrite cores because it has
A. High specific gravity
B. High resistance
C. High hysteresis
D. low permeability


[2] Harmonics in transformer result in
A. Increased core losses
B. Increased I2R losses
C. Magnetic interference with communication circuits
D. All of the above


[3] The full load copper loss of a transformer is 1600W. At half-load the copper loss will be
A. 6400W
B. 1600W
C. 800W
D. 400W


[4] Power transformers are generally designed to have maximum efficiency around
A. No load
B. Half load
C. Near full load
D. 10% overload


[5] Two transformers are connected in parallel. These transformers do not have equal percentage impedance which results
A. Short-circuiting of the secondaries
B. Power factor of one of the transformers is leading while that of the other lagging
C. Transformers having higher copper losses will have negligible core losses
D. Loading of the transformers not in proportion to their kVA ratings.


[6] The changes in volume of transformer cooling oil due to variation of atmospeheric temperature during day and night is taken care of by which part of transformer?
A. Conservator
B. Breather
C. Bushings
D. Buchholz relay


[7] The transformer laminations are insulated from each other by
A. Mica strip
B. Thin coat of varnish
C. Paper
D. Any of the above


[8] Which type of winding is used in 3 phase shell type transformer?
A. Circular type
B. Sandwich type
C. Cylindrical type
D. Rectangular type


[9] During open circuit test of a transformer
A. Primary is supplied rated voltage
B. Primary is supplied full load current
C. Primary is supplied current at reduced voltage
D. Primary is supplied rated kVA


[10] Which of the following is not standard voltage for power supply in India
A. 11kV
B. 33kV
C. 66 kV
D. 122 kV


[11] The low voltage winding of a 400/230 volt, 1-phase, 50Hz transformer is to be connected to a 25Hz supply in order to keep the magnetization current at the same level as that for normal 50Hz supply at 25Hz the voltage should be [Gate 1997]
a) 230V
b) 460V
c) 115V
d) 65V

[12] The primary current in the current transformer is dictated by [Gate 1997]
a) The secondary burden
b) The core of the transformer
c) The load current
d) None of the above


10:26 PM
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30 comments:

  1. UnknownAugust 25, 2013 at 3:53 AM

    In ferrite core T/ f in use for to reduce iron losses
    but answer given reduce resistance how ?
    Plz. Clear

    ReplyDelete
  2. UnknownAugust 25, 2013 at 3:53 AM

    In ferrite core T/ f in use for to reduce iron losses
    but answer given reduce resistance how ?
    Plz. Clear

    ReplyDelete
    Replies
    1. UnknownOctober 2, 2013 at 11:12 PM

      ferrite core t/f already have high resistence and no need of laminations like silicon steel core t/f .due to high ferrite resistence decrease the eddy current losses.

      Delete
    2. UnknownOctober 2, 2013 at 11:15 PM

      Ferrite core have high resistence

      Delete
    3. UnknownNovember 10, 2013 at 9:44 AM

      Ferrite core has high resistivity .so it has high resistance which results in the reduction of eddy current. So eddy current losses can be reduced which is predominant at high frequencies. That is why ferrite cores are used in high frequency transformer.

      Delete
    4. AnonymousOctober 6, 2017 at 9:41 AM

      yes i am also want of explanation

      Delete
  3. UnknownSeptember 12, 2013 at 11:27 PM

    Good

    ReplyDelete
  4. UnknownOctober 20, 2013 at 11:12 AM

    very help full..thanks

    ReplyDelete
  5. UnknownOctober 26, 2013 at 1:34 AM

    Very usefull thanks alot

    ReplyDelete
  6. UnknownNovember 23, 2013 at 9:57 AM

    Good

    ReplyDelete
  7. UnknownNovember 23, 2013 at 9:58 AM

    Good

    ReplyDelete
  8. UnknownNovember 23, 2013 at 9:58 AM

    This comment has been removed by a blog administrator.

    ReplyDelete
  9. UnknownNovember 23, 2013 at 9:59 AM

    This comment has been removed by a blog administrator.

    ReplyDelete
  10. UnknownNovember 24, 2013 at 10:12 PM

    thank u .
    can u provide answers with justifications

    ReplyDelete
  11. UnknownDecember 1, 2013 at 7:58 PM

    Very usefull thanks

    ReplyDelete
  12. AnonymousFebruary 1, 2014 at 10:13 PM

    very usefull information thanks

    ReplyDelete
  13. bimal* 27.06.2014June 26, 2014 at 11:36 PM

    kindly clear q.11 *

    ReplyDelete
  14. AnonymousAugust 30, 2014 at 3:16 AM

    a11>E directly proportional to f for constant value of phi..
    e1/e2=f1/f2
    230/e2=50/25
    e2=115

    ReplyDelete
  15. UnknownSeptember 14, 2014 at 7:32 AM

    It's useful. Thank you very much.

    ReplyDelete
  16. AnonymousJune 7, 2015 at 10:24 AM

    very useful ,thanks

    ReplyDelete
  17. AnonymousJune 9, 2015 at 5:34 AM

    nice
    send as many questions with answers as possible to you

    ReplyDelete
  18. UnknownApril 7, 2016 at 9:18 PM

    Thanks

    ReplyDelete
  19. Govardhan December 13, 2016 at 4:19 AM

    [11] The low voltage winding of a 400/230 volt, 1-phase, 50Hz transformer is to be connected to a 25Hz supply in order to keep the magnetization current at the same level as that for normal 50Hz supply at 25Hz the voltage should be [Gate 1997]
    a) 230V
    b) 460V
    c) 115V
    d) 65V
    Ans: C
    Manetising current cant be analysed theoritically it can be guessed
    if u have brief discussion u can say..

    ReplyDelete
  20. UnknownApril 4, 2017 at 4:04 AM

    question 12 ans ..... justification ....????

    ReplyDelete
  21. UnknownApril 16, 2017 at 2:11 AM

    QN no. 12 correct ans is C

    ReplyDelete
  22. AnonymousApril 16, 2017 at 2:13 AM

    1 c

    ReplyDelete
  23. AnonymousApril 24, 2017 at 1:05 AM

    Nice.... Very helpful

    ReplyDelete
  24. UnknownJuly 2, 2017 at 8:04 AM

    12-c

    ReplyDelete
  25. UnknownJuly 7, 2017 at 12:12 AM

    I THINK Q-12 IS C CORRECT

    ReplyDelete
  26. UnknownJuly 12, 2017 at 12:13 PM

    i thing q-12 is c right answer

    ReplyDelete

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