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MCQ of D.C motor page-4

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29. In case of regenerative braking, the motor

a) Dissipates energy in armature circuit
b) Dissipates energy in field circuit
c) Both (a) and (b)
d) Supply energy to source

Ans: (d)

30. If plugging is applied to series motor for a long time, then

a) It will start revolving in other direction at low speed
b) Motor will stop
c) Motor will burn
d) None of these

Ans: (a)

31. Disadvantage of the field-control method of speed control is

a) That speed above normal speed can be achieved
b) That commutation becomes unsatisfactory
c) Its low efficiency
d) None of these

Ans: (b)

32. Speed regulation of a d.c. motor can be ideally achieved with

a) A.C. excitation to the field of the motor
b) Variable excitation to the field of the motor
c) constant excitation to the field of the motor
d) no excitation to the field of the motor

Ans: (c)

33. Disadvantage of ward-Leonard system is

a) increased maintenance cost
b) its high initial cost
c) its low efficiency at light loads
d) all of them

Ans: (d)

34. Ward-Leonard method is basically a

a) field diverter method
b) field control method
c) armature resistance control method
d) voltage control method

Ans: (d)

35. In ward-Leonard system, minimum number of machines required are

a) two
b) three
c) four
d) five

Ans: (b)

36. Ward-Leonard method of speed control is basically usefully where usually

a) wide range of sensitive speed control is required
b) wide range of speed control is required
c) narrow range of speed control is required
d) none of these

Ans: (a)

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