Industrial Motor Control
7th Edition
ISBN: 9781133691808
Author: Stephen Herman
Publisher: Cengage Learning
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Textbook Question
Chapter 3, Problem 1RQ
A single-phase, 120 volt motor is controlled by a manual motor starter. The motor is not running, and the switch handle on the starter is found to be in the center position. What does this indicate?
Expert Solution & Answer
To determine
The indication of center position of switch handle of a manual motor starter.
Explanation of Solution
Manual motor starter is simple and common motor starter. Operator involvement is must to change the state of a manual motor starter. A manual motor starter is looks like a simple toggle switch. In addition, the manual motor starters are come up with overload protectors. Thus, the manual motor starter has three positions namely ON, OFF, and over load protection.
The two end positons of the toggle lever of a manual motor starter indicates ON and OFF positions. The center position indicates that the motor is tripped due to over load. Whenever the current flows in a circuit, a proportionate heat is generated in a conductor. When a motor is over loaded, more current will flow, heat generation is high. If this continues, the motor will fail. Thus, the overload heater (protector) is involved. The over load protector is designed for normal operating condition. When a motor runs abnormally (over loading), the over load protector stops the power supply to the motor. Thereby, the toggle lever (switch handle) moved to center position.
Hence, the center position of switch handle of a manual motor starter denotes that the motor is tripped due to over load.
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Q1: Determine the length, angle of contact, and width of a 9.75 mm thick
leather belt required to transmit 15 kW from a motor running at 900 r.p.m. The
diameter of the driving pulley of the motor is 300 mm. The driven pulley runs at
300 r.p.m. and the distance between the centers of two pulleys is 3 meters. The
density of the leather is 1000 kg/m³. The maximum allowable stress in the
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5. A 15 kW and 1200 r.p.m. motor drives a compressor at 300 r.p.m. through a pair of spur gears having
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Check the gears thus designed from the consideration of wear. The surface endurance limit may be
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Chapter 3 Solutions
Industrial Motor Control
Ch. 3 - A single-phase, 120 volt motor is controlled by a...Ch. 3 - Prob. 2RQCh. 3 - Prob. 3RQCh. 3 - A push button manual starter has tripped on...Ch. 3 - What is meant by the term line voltage on some...Ch. 3 - Explain the difference between manual motor...Ch. 3 - Prob. 7RQCh. 3 - Prob. 8RQCh. 3 - Refer to the circuit shown in Figure 310. When...Ch. 3 - Prob. 10RQ
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