221) Which of the following losses are significantly reduced by laminating the core of a DC generator ?

  1. Hysteresis losses
  2. Eddy current losses
  3. Copper losses
  4. Windage losses
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

222) The total losses in a well designed DC generator of 10 kW will be nearly______________?

  1. 100 W
  2. 500 W
  3. 1000 W
  4. 1500 W
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

223) The condition for maximum efficiency for a DC generator is______________?

  1. Eddy current losses = stray losses
  2. Hysteresis losses = eddy current losses
  3. Copper losses = 0
  4. Variable losses = constant losses
ANSWER
Answer: ( 4 )
EXPLANATION
No answer description required for this question.

224) DC generators are normally designed for maximum efficiency around_____________?

  1. Full-load
  2. Rated r.p.m.
  3. Rated voltage
  4. All of the above
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

225) In a DC generator, the iron losses mainly take place in___________

  1. Yoke
  2. Commutator
  3. Armature conductors
  4. Armature rotor
ANSWER
Answer: (41 )
EXPLANATION
No answer description required for this question.

226) DC generators are installed near the load centres to reduce_____________?

  1. Iron losses
  2. Line losses
  3. Sparking
  4. Corona losses
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

227) The purpose of retardation test on DC shunt machines is to find out____________?

  1. Stray losses
  2. Eddy current losses
  3. Field copper losses
  4. Windage losses
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

228) Which of the following tests will be suitable for testing two similar DC series motors of large capacity ?

  1. Swinburne’s test
  2. Hopkinson’s test
  3. Field test
  4. Brake test
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

229) During rheostat braking of DC series motors_____________?

  1. Motor is run as a generator
  2. Motor is reversed in direction
  3. Motor is run at reduced speed
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

230) For which types of DC motor, dynamic braking is generally used ?

  1. Shunt motors
  2. Series motors
  3. Compound motors
  4. All of the above
ANSWER
Answer: ( 4 )
EXPLANATION
No answer description required for this question.

231) Which method of braking is generally used in elevators ?

  1. Plugging
  2. Regenerative braking
  3. Rheostatic braking
  4. None of the above
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

232) In variable speed motor___________?

  1. A stronger commutating field is needed at low speed than at high speed
  2. A weaker commutating field is needed at low speed than at high speed
  3. Same commutating field is needed at low speed than at high speed
  4. None of the above is correct
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

233) When the armature of a DC motor rotates, e.m.f. induced is___________?

  1. Self-induced e.m.f.
  2. Mutually induced e.m.f.
  3. Back e.m.f
  4. None of the above
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

234) Where DC motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control______________?

  1. Drum type controller is used
  2. Three point starter is used
  3. Four point starter is used
  4. All above can be used
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

235) If a DC shunt motor is working at full load and if shunt field circuit suddenly opens____________?

  1. This will make armature to take heavy current, possibly burning it
  2. This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
  3. Nothing will happen to motor
  4. Motor will come to stop
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

236) DC motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________?

  1. Series motor
  2. Shunt motor
  3. Compound motor
  4. Any of the above
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

237) DC motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this______________?

  1. Series motor
  2. Shunt motor
  3. Compound motor
  4. Any of the above
ANSWER
Answer: ( 3 )
EXPLANATION
No answer description required for this question.

238) Which DC motor has got maximum self relieving property ?

  1. Series motor
  2. Shunt motor
  3. Cumulatively compounded motor
  4. Differentially compounded motor
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

239) In the DC motor the iron losses occur in____________?

  1. The field
  2. The armature
  3. The brushes
  4. The commutator
ANSWER
Answer: ( 2 )
EXPLANATION
No answer description required for this question.

240) The speed of a DC shunt motor is required to be more than full load speed. This is possible by______________?

  1. Reducing the field current
  2. Decreasing the armature current
  3. Increasing the armature current
  4. Increasing the excitation current
ANSWER
Answer: ( 1 )
EXPLANATION
No answer description required for this question.

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