Industrial Motor Control
7th Edition
ISBN: 9781133691808
Author: Stephen Herman
Publisher: Cengage Learning
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Chapter 37, Problem 3RQ
Refer to the circuit shown in Figure 37–1. Assume that timer TR is set for a delay of 10 seconds. When the Start button is pressed, the motor starts in low speed. After a delay of 30 seconds, the motor is still in its lowest speed and has not accelerated to normal speed. Which of the following could not cause this condition?
- a. The Start button is shorted.
- b. Timer coil TR is open.
- c. Contactor coil R is open.
- d. Timed contact TR did not close after a delay of 10 seconds.
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A piston–cylinder device contains 3 kg of nitrogen initially at 100 kPa and 25°C. Nitrogen is now compressed slowly in a polytropic process during which PV1.3 = constant until the volume is reduced by one-half. Determine the work done and the heat transfer for this process. The gas constant of N2 is R = 0.2968 kPa·m3/kg·K. The cv value of N2 at the anticipated average temperature of 350 K is 0.744 kJ/kg·K (Table A-2b).
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Industrial Motor Control
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