Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Textbook Question
Chapter 2, Problem 1SQ
If the contacts on a manual starter cannot be closed immediately after a motor overload has tripped them open, what is the probable reason?
Expert Solution & Answer
To determine
Explain the probable reason for allowing the time duration to reset the starter contacts after they tripped off by the overload protection equipment of the motor.
Explanation of Solution
Discussion:
The overload protection of the motor trips off (open) the contacts of a motor starter when the load exceeds the normal range. The overload protection equipment (heater) gets heated during the overload condition.
The contacts of the starter can reset only after the overload protection equipment cools completely. If the contacts are closed immediately, the heater does not cool properly due to the insufficient time and it lead to damage the motor as the overload still exists.
Conclusion:
Thus, the contacts of the motor starter cannot close immediately when the motor overload has tripped them open.
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Students have asked these similar questions
A communication satellite is in stationary (synchronous) orbit about the earch (assume
altitude of 22.300 statute miles). Its transmitter generates 8.0 W. Assume the transmit-
ting antenna is isotropic. Its signal is received by the 210-ft diameter tracking parabo-
loidal antenna on the earth at the NASA tracking station at Goldstone, California. Also
assume no resistive loss in either antenna, perfect polarization match, and perfect
impedance match at both antennas. At a frequency of 2 GHz. determine the:
(a) power density (in watts/m²) incident on the receiving antenna.
(b) power received by the ground-based antenna whose gain is 60 dB.
Don't use ai to answer I will report you answer
A plane wave traveling in z-direction through a medium with &=8, μ-2 and has
the electric and magnetic field intensity at z=0 shown in Fig. 6.1 and Fig. 6.2, respectively. Utilize the
provided information to find the following:
(a) w
(b) The intrinsic impedance of the medium
© B
(d) a
(e) The expression of the magnetic field intensity, H
(f) The time-average power carried by the wave
Magnetic Field Intensity (mA/m)
Electric Field Intensity (V/m)
0.5
0.4-
0.3
0.2
ཧཱུྃ༔ཤྲུསྦྱ ཌུ ཋ ; སྟྲི " ° ཝཱ
0.1
-0.5
Ex
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Fig 6.2
Hy
2.0
Time (ns)².
-2.0
-1.5
-1.0
-0.5
0.0;
0.5
1.0
Time (ns)
2.0
0.083 ns or 0.0415 T
Chapter 2 Solutions
Electric Motor Control
Ch. 2 - If the contacts on a manual starter cannot be...Ch. 2 - If the handle of an installed motor starter is in...Ch. 2 - How may an automatic operation be achieved when a...Ch. 2 - What does the term trip-free mean as it relates to...Ch. 2 - Prob. 5SQCh. 2 - Prob. 6SQCh. 2 - Prob. 7SQCh. 2 - Prob. 8SQCh. 2 - Select the best answer for each of the following....Ch. 2 - Select the best answer for each of the following....
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