Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Textbook Question
Chapter 30, Problem 1RQ
Name three methods of braking a motor.
Expert Solution & Answer
To determine
Identify three methods of braking a motor.
Explanation of Solution
The motors are generally slowed to stop by disconnecting thee power supplied. But, there are instances where that is not convenient. In these instances, brakes are applied to the motor to slow or stop the motor.
Some of the methods of braking a motor are:
- Mechanical brakes.
- Dynamic brakes.
- Plugging.
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2. A spur gear made of bronze drives a mid steel pinion with angular velocity ratio of 32: 1. The
pressure angle is 14½. It transmits 5 kW at 1800 r.p.m. of pinion. Considering only strength, design
the smallest diameter gears and find also necessary face width. The number of teeth should not be less
than 15 teeth on either gear. The elastic strength of bronze may be taken as 84 MPa and of steel as 105
MPa. Lewis factor for 14½½ pressure angle may be taken
0.684
0.124
y =
No. of teeth
as
[Ans. m 3 mm; b= 35 mm; Dp = 48 mm; D= 168 mm]
Q2. Determine the safety factors for the bracket rod shown in Figure 2 based on both the
distortion-energy theory and the maximum shear theory and compare them.
Given: The material is 2024-T4 aluminum with a yield strength of 47 000 psi.
The rod length /= 6 in. and arm a = 8 in. The rod outside diameter od 1.5 in., id = 1 in, h=2 in.,
t=0.5 in., Load F= 1000 lb.
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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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