Understanding Motor Controls
3rd Edition
ISBN: 9781305498129
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 4, Problem 1RQ
To determine
Identify the two basic types of overload relays.
Expert Solution & Answer
Explanation of Solution
Overload relays are used to protect the motor from overloading by sensing the current flow in the motor.
The two basic types of overload relays are as follows:
- Thermal overload relay
- Magnetic overload relay
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Chapter 4 Solutions
Understanding Motor Controls
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- What pin numbers are connected to the coil of an 8-pin control relay?arrow_forwardWhy is it necessary to permit a solder melting type of overload relay to cool for two to three minutes after it has tripped?arrow_forwardRefer to Figure 211 to answer the following questions. How much voltage will be applied to coil 1CR when it is energized?arrow_forward
- An 11-pin control relay contains three sets of single-pole double throw contacts. List the pin numbers by pairs that can be used as normally open contacts.arrow_forwardList some of the protective relays found with large transformers.arrow_forwardHow many transformers are needed to make an open-delta connection?arrow_forward
- Name three factors that determine the amount of induced voltage.arrow_forwardState the physical differences between a run and a start capacitor.arrow_forwardA large motor has a full load current rating of 425 amperes. Current transformers with a ratio of 600:5 are used to reduce the current to the overload heaters. What should be the full load current rating of the overload heaters?arrow_forward
- Name two methods of sensing the current flow through the shunt field.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_forwardWhat is the average voltage drop of an SCR when it is turned on?arrow_forward
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