Industrial Motor Control
7th Edition
ISBN: 9781133691808
Author: Stephen Herman
Publisher: Cengage Learning
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Textbook Question
Chapter 39, Problem 1RQ
Name two requirements that must be met before a motor can be used for wye–delta starting.
Expert Solution & Answer
To determine
The requirements that must be met before the motor is used for the wye delta starting.
Explanation of Solution
Consider that delta starting is often used to reduce the inrush current in to the motor and at the starting to reduce the starting torque.
Consider the requirement for the motor to be used for the wye delta starting is,
The motor designed for the stator winding must be in delta during the running period.
The leads of the stator winding should be accessible.
Therefore, the requirements of the motor to start by the use of the wye delta starting is discussed.
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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.
Choose the motor from the range of options that is most fit for purpose.
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)=
Percentage slip (%) =
Most suitable motor from given range (kW)-
State four advantages of a pre-engaged starter when compared with an inertia type.
Chapter 39 Solutions
Industrial Motor Control
Ch. 39 - Name two requirements that must be met before a...Ch. 39 - Prob. 2RQCh. 39 - Prob. 3RQCh. 39 - Refer to the circuit shown in Figure 399. Assume...Ch. 39 - Refer to the circuit shown in Figure 39–9. Assume...Ch. 39 - Prob. 6RQCh. 39 - The motor nameplate of a wye–delta starter motor...Ch. 39 - Prob. 8RQCh. 39 - Refer to the circuit shown in Figure 3914. What is...Ch. 39 - Refer to the circuit shown in Figure 39–14. When...
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