A 2300-V 1000-hp 0.8-PF leading 60-Hz two-pole Y-connected synchronous motor has a synchronous reactance of 2.8 2 and an armature resistance of 0.4 2. At 60 Hz, its friction and windage losses are 24 kW, and its core losses are 18 kW. The field circuit has a de voltage of 200 V, and the maximum I, is 10 A. The open-circuit characteristic of this motor is shown in Figure P6-1. Answer the following questions about the motor, assuming that it is being supplied by an infinite bus. (a) How much field current would be required to make this machine operate at unity power factor when supplying full load? (b) What is the motor's efficiency at full load and unity power factor? (c) If the field current were increased by 5 percent, what would the new value of the armature current be? What would the new power factor be? How much reactive power is being consumed or supplied by the motor? (d) What is the maximum torque this machine is theoretically capable of supplying at unity power factor?

A 2300-V 1000-hp 0.8-PF leading 60-Hz two-pole Y-connected synchronous motor has a synchronous reactance of 2.8 2 and an armature resistance of 0.4 2. At 60 Hz, its friction and windage losses are 24 kW, and its core losses are 18 kW. The field circuit has a de voltage of 200 V, and the maximum I, is 10 A. The open-circuit characteristic of this motor is shown in Figure P6-1. Answer the following questions about the motor, assuming that it is being supplied by an infinite bus. (a) How much field current would be required to make this machine operate at unity power factor when supplying full load? (b) What is the motor's efficiency at full load and unity power factor? (c) If the field current were increased by 5 percent, what would the new value of the armature current be? What would the new power factor be? How much reactive power is being consumed or supplied by the motor? (d) What is the maximum torque this machine is theoretically capable of supplying at unity power factor?

Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List)

10th Edition

ISBN:9781337399128

Author:Russell E. Smith

Publisher:Russell E. Smith

Chapter8: Basic Electric Motors

Section: Chapter Questions

Problem 26RQ

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Question

(A)
260
250
240
230
220
200
210
350
D
400
450
Synchronous Motor V-Curve
500
E (V)
550
600
650
700
A 2300-V 1000-hp 0.8-PF leading 60-Hz two-pole Y-connected synchronous motor has a synchronous
reactance of 2.8 2 and an armature resistance of 0.4 2. At 60 Hz, its friction and windage losses are 24
kW, and its core losses are 18 kW. The field circuit has a de voltage of 200 V, and the maximum 1, is 10
A. The open-circuit characteristic of this motor is shown in Figure P6-1. Answer the following questions
about the motor, assuming that it is being supplied by an infinite bus.
(a) How much field current would be required to make this machine operate at unity power factor when
supplying full load?
(b) What is the motor's efficiency at full load and unity power factor?
(c) If the field current were increased by 5 percent, what would the new value of the armature current be?
What would the new power factor be? How much reactive power is being consumed or supplied by the
motor?
(d) What is the maximum torque this machine is theoretically capable of supplying at unity power factor?
At 0.8 PF leading?

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