Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Textbook Question
Chapter 26, Problem 1RQ
Name two requirements that must be met before a motor can be used for wye-delta starting.
Expert Solution & Answer
To determine
Identify two requirements for a motor to be used with wye-delta starting.
Explanation of Solution
Wye-delta starting is used to reduce the inrush current and the starting torque. The two requirements for a motor to be used with wye-delta starting are:
- The design of the motor must be such that the stator winding is connected in delta during the running time.
- All the leads of the stator windings must be accessible.
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State four advantages of a pre-engaged starter when compared with an inertia type.
A 50 Hz pump drive requires a torque of 70 Nm approx. at 1450 rpm approx. for 1 minute followed by 5 minutes running
unloaded. This cyclic pattern is repeated continuously. The motor is to be selected from a range of general-purpose motors
with continuous ratings of 2.2, 3, 4, 5.5, 7.5, 11, 15 and 20 kW. The motors have a pull-out torque of 200%.
1.
Select the pole number.
2.
Calculate the continuous power rating.
3.
4.
Calculate the required power rating given the pull out torque rating.
Estimate the slip when the motor drives the pump at the required speed.
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5.
Enter your answers in the units indicated (without unit symbols) corrected if necessary to two decimal places.
Answer:
Number of poles=
✓
Continuous power rating (kW)=
Required power rating for 200% pull out torque (kW)=
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Chapter 26 Solutions
Understanding Motor Controls
Ch. 26 - Name two requirements that must be met before a...Ch. 26 - Prob. 2RQCh. 26 - Prob. 3RQCh. 26 - Refer to the circuit shown in Figure 26–9. Assume...Ch. 26 - Refer to the circuit shown in Figure 269. Assume...Ch. 26 - Prob. 6RQCh. 26 - The motor nameplate of a wye-delta started motor...Ch. 26 - Prob. 8RQCh. 26 - Refer to the circuit shown in Figure 2614. What is...Ch. 26 - Refer to the circuit shown in Figure 2614. When...
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