Sunday, April 14, 2013

Transformers Objective Questions: Part-8

[1] The degree of mechanical vibrations produced by the laminations of a transformers depends on
A. Tightness of clamping
B. Gauge of laminations
C. Size of laminations
D. All of the above

[2] The no-load current drawn by transformer is usually........percent of the full-load current?
A. 0.2 to 0.5 %
B. 2 to 5%
C. 12 to 15 %
D. 20 to 30 %

[3] The dielectric strength of transformer oil is expected to be
A. 1kV
B. 33kV
C. 100kV
D. 330 kV

[4] During the short-circuit test on a small transformer the frequency is increased from 50-200Hz. The copper losses will increase by a factor of
A. 16
B. 4
C. 1
D. 1/4

[5] No-load current in a transformer
A. Lags behind the voltage by about 75 deg
B. Leads the voltage by about 75
C. Lags behind the voltage by about 15
D. Leads the voltage by about 15

[6] While conducting short-circuit test on a transformer the following side is short circuited
A. High voltage side
B. Low voltage side
C. Primary side
D. Secondary side

[7] The chemical used in breather for transformer should have the quality of
A. Ionizing air
B. Absorbing moisture
C. Cleansing the transformer oil
D. Cooling the transformer oil

[8] If a pump motor is run on 2/3rd of its supply voltage, it will
A. Continue to deliver same power
B. Burn
C. Stall
D. Continue to run at lower speed

[9] An ideal transformer has infinite values of primary and secondary inductances. The statement is
A. True
B. False

[10] The noise resulting from vibrations of laminations set by magnetic force, is termed as
A. Magnetostriction
B. Boo
C. Hum
D. Zoom


12:35 AM

5 comments:

  1. During the short-circuit test on a small transformer the frequency is increased from 50-200Hz. The copper losses will increase by a factor of ........
    how the factor is 16?

    ReplyDelete
    Replies
    1. Pcu is directly proportional to square of frequency

      Delete
  2. bimal *27.06.2014June 27, 2014 at 3:04 AM

    Thanks for such gud questions *

    ReplyDelete
  3. the low voltage of a 400/230 V single phase 50Hz transformer is to be connected to keep the magnetization current at the same level in both cases the voltage of 25Hz should be

    ReplyDelete