Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Chapter 30, Problem 12RQ
To determine
Identify the device used to accurately stop a motor when using a plugging stop.
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Chapter 30 Solutions
Understanding Motor Controls
Ch. 30 - Name three methods of braking a motor.Ch. 30 - How is the braking force of drum type brakes...Ch. 30 - Why are mechanical brakes often used on cranes?
Ch. 30 - What is the advantage of dynamic brakes over...Ch. 30 - What is the disadvantage of dynamic brakes when...Ch. 30 - The amount of counter torque developed by a direct...Ch. 30 - When using dynamic braking for a direct current...Ch. 30 - Name three factors that determine the amount of...Ch. 30 - How is dynamic braking for direct current motors...Ch. 30 - How is the dynamic braking force of an alternating...
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- What is the difference between a motor starter and a contactor?arrow_forwardName two requirements that must be met before a motor can be used for wye-delta starting.arrow_forwardWhen a repulsion-start induction-run motor reaches about 75% of rated full-load speed, it stops operating as a repulsion motor and starts operating as a squirrel-cage motor. What must be done to cause the motor to begin operating as a squirrel-cage motor?arrow_forward
- What type of single-phase motor develops the highest starting torque?arrow_forwardWhen energizing or de-energizing a combination starter what safety precaution should always be taken?arrow_forwardRefer to the schematic diagram in Figure 318. Assume that the motor is not running. When the third speed push button is pressed, the motor starts in its lowest speed. After a delay of 3 seconds, the motor accelerates to second speed and 3 seconds later to third speed. After a period of about 1 minute, the fourth speed push button is pressed, but the motor does not accelerate to fourth speed. Which of the following could cause this problem? a. Control relay CR2 coil is open. b. S2 contactor coil is open. c. CR3 coil is shorted. d. S3 contactor coil is open.arrow_forward
- An open winding in an electric motor means that A. the winding is making contact with the motor frame. B. one winding is making contact with another winding. C. a wire in one winding is broken. D. the centrifugal switch to the start winding is open.arrow_forwardAssume that all three motors shown in Figure 12–14 are running. Now assume that the STOP button is pressed and motors #1 and #2 stop running, but motor #3 continues to operate. Which of the following could cause this problem? STOP button is shorted. The 2M contact between wire numbers 31 and 32 is hung closed. The 3M load contacts are welded shut. The normally open 3M contact between wire numbers 23 and 31 is hung closed.arrow_forwardWhat type of armature winding is generally used for machines designed to operate on low voltage and high current?arrow_forward
- True or False: If a sleeve bearing fails in a small, fractional horsepower motor, the motor is generally replaced.arrow_forwardWhich of the following devices may be wired into the starting circuit of a motor to improve the starting torque? A. Another winding B. A start capacitor C. A thermostat D. A winding thermostatarrow_forwardWhat type of commutator is used with a brush-lifting repulsion-start induction-run motor?arrow_forward
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