171. The most inefficient method for speed control of dc motor is
- voltage control
- field control
- armature control
- none of the above
172. A dc shunt motor is operating at no load. If the armature is shunted by a resistance, its speed will
- increase
- decrease
- remain the same
- be unpredictable
173. The armature voltage control is consider suitable for a dc motor driven at constant
- torque
- speed
- power
- current
174. In a ward-leonard drive, if the field current of the dc generator is suddenly reduced, the controlled dc motor operates
- still in the motoring mode
- in dynamic braking mode
- in counter-current braking mode
- in regenerative braking mode
175. Ward-Leonard system for controlling the speed of the dc motor is used where
- the speed in both the direction is required
- very fine speed control over the whole range from zero to normal speed is required
- the accuracy in speed control is required
- all of the above
176. Variation in speed by ward-leonard control of dc motors occurs due to variation in
- field excitation
- armature current
- armature voltage
- supply voltage
177. Ward-Leonard control is basically a ______ control method.
- armature voltage
- field
- field divertor
- armature resistance
178. For very sensitive and wide speed control, the preferable control method is
- field control
- armature control
- multiple voltage control
- ward-leonard system
179. In ward-leonard system, the lower limit of speed is imposed by
- armature resistance
- field resistance
- residual magnetism of the generator
- none of the above
180. In ward-leonard method of speed control, the direction of rotation of the motor is reversed usually by reversing the connection of the
- generator field terminals
- generator armature terminals
- motor armature terminals
- motor field terminals
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