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Question 4 i. Explain how just the synchronous reactance and armature resistance can be determined in a synchronous generator. ii. A 200 hp, 460-V, 60-Hz, 1760 rpm, four-pole, Y-connected induction motor has a power factor of 0.85 lagging and an efficiency of 90% at full load. If started with rated voltage, the starting current is six times larger than the full load current of the motor. An autotransformer is used to start the motor at reduced voltage. (a) Determine the full-load motor current (b) Determine the autotransformer output voltage to make the starting motor current twice the full load current. (c) Determine the ratio of the starting torque at the reduced voltage of part (b) to the torque at rated voltage.

          Question 4
i. Explain how just the synchronous reactance and armature resistance can be determined in a
synchronous generator.
ii. A 200 hp, 460-V, 60-Hz, 1760 rpm, four-pole, Y-connected induction motor has a power factor
of 0.85 lagging and an efficiency of 90% at full load. If started with rated voltage, the starting
current is six times larger than the full load current of the motor. An autotransformer is used
to start the motor at reduced voltage.
(a) Determine the full-load motor current
(b) Determine the autotransformer output voltage to make the starting motor current twice the
full load current.
(c) Determine the ratio of the starting torque at the reduced voltage of part (b) to the torque at
rated voltage.

Question 4
i. Explain how just the synchronous reactance and armature resistance can be determined in a
synchronous generator.
ii. A 200 hp, 460-V, 60-Hz, 1760 rpm, four-pole, Y-connected induction motor has a power factor
of 0.85 lagging and an efficiency of 90% at full load. If started with rated voltage, the starting
current is six times larger than the full load current of the motor. An autotransformer is used
to start the motor at reduced voltage.
(a) Determine the full-load motor current
(b) Determine the autotransformer output voltage to make the starting motor current twice the
full load current.
(c) Determine the ratio of the starting torque at the reduced voltage of part (b) to the torque at
rated voltage.

Added by Kelsey B.

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