Electrical machine MCQ #5
1) The high leakage impedance transformers are suitable for the
applications of
(a)
Arc welding
(b) Electric lamp
(c)
Personal computers
(d)
Street lights
2) For the parallel operation of transformers, the PU impedances
of the transformer must be (based on their own kVA rating)
(a) equal
(b) directly proportional to their ratings
(c) inversely proportional to their ratings
(d) none of these
3) Which test is also called as back to backtest?
(a) Retardation test
(b) Sumpner's test
(c) Voltage drop test
(d) Field test
4) For maximum efficiency in a transformer
(a) Core losses = 2 * copper losses
(b) Core losses = copper losses / 2
(c) Core losses = copper losses
(d) Core losses = copper losses ∧
2
5) For an ideal transformer winding resistances and leakage flux
should be
(a) Least, maximum
(b) Both should be maximum
(c) Both should be zero
(d) Maximum, least
ANSWER: |1-A | 2-A | 3-B |
4-C | 5-C |
6) With the increase in load, the speed of the synchronous motor
(a) Increases
(b) Decreases
(c) Remains constant
(d) None of the above
7) A synchronous motor is started by using damper winding. When the
motor runs at synchronous speed then the induced emf in the damper winding will
be
(a) Zero
(b) Maximum
(c) Half of the terminal voltage
(d) None of these
8) The method used to determine Xd and Xq, the direct and
quadrature axis reactance is called
(a) Reactance test
(b) Blondel’s two reaction theory
(c) Slip test
(d) All of the above
9) The synchronous generator
supplies a leading power factor and
lagging power factor respectively when it is
(a) Overexcited,
under excited
(b) Overexcited,
over excited
(c) Under excited, under excited
(d) Under excited, over excited
10) The direct method for
finding the voltage regulation of an alternator is/are
(a) E.M.F method
(b) M.M.F. method
(c) Z.P.F method
(d) None of these
ANSWER: | 6-C
| 7-A | 8-C | 9-D | 10-D |
11) The cheapest starter for
the induction motor is
(a) Stator resistance starter
(b) Autotransformer starter
(c) Star-delta starter
(d) Rotor resistance starter
12) When the induction motor runs faster than the synchronous
speed, the induction motor runs as
(a) Induction generator
(b) Synchronous motor
(c) Asynchronous generator
(d) Such a condition
is not possible
13) In a slip ring induction motor, the rotor resistance is _____
starting and _____ normal operating speed.
(a) Remains same during, low at
(b) Low, high at
(c) High during, low at
(d) None of these
14) In the blocked rotor tests, the slip is equal to
(a) 0
(b) 1
(c) 0.5
(d) 0.707
15) Crawling is a phenomenon
mainly associated with
(a) 3rd harmonic
(b) 5th harmonic
(c) 7th harmonic
(d) 2nd harmonic
ANSWER: | 11-C | 12-A | 13-C
| 14-B | 15-C |
All questions are useful to exam point of view
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