Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Textbook Question
Chapter 17, Problem 22RQ
A three-phase squirrel-cage motor is connected to a 60-Hz line. The full-load speed is 870 RPM. How many poles per phase does the stator have?
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QUESTION 8
Consider the equations of motion of an armature controlled DC motor given by
Jw(t)+bw (t) Ki(t) = -Tfriction - Tload (t)
di (t)
+ Ri (t) + Kw (t) =
Vin (t),
dt
where vin(t) is the input voltage and Tload(t) is the input load torque. The outputs are the armature current i(t) and the motor speed w(t).
The steady-state response of motors are specified by nominal voltage, stall torque, stall current, no load speed, and no load current.
At steady-state operation, the motor equations satisfy
bo) -Ki =-T -T.
fric
load
Ri +Kov_-
55
55
The stall torque is the load torque required stead-state speed of the motor is zero.
The stall current is the armature current when the motor speed is zero.
The no load speed is the speed of motor when the load torque is zero.
The no load current is the current when the load torque is zero.
What is stall torque for this motor in N-m? Keep 3 significant figures, and do not include units. Use Scientific notation.
The constants are given below.
Nominal…
As shown in the figure below, this is a speed regulation method for DC separately excited
motor.
a) What is the speed regulation method?
b) What are the characteristics for this speed regulation method?
B
no
Ra
le
lo
R:
'3
E
R3
Tr.
T
Calculate the percentage speed regulation of a motor at full load if the machine runs at 1000 rpm at no-load and the full load speed is 900 rpm.
Chapter 17 Solutions
Electrical Transformers and Rotating Machines
Ch. 17 - Prob. 1RQCh. 17 - Prob. 2RQCh. 17 - What is synchronous speed?Ch. 17 - What two factors determine synchronous speed?Ch. 17 - Name three factors that cause the magnetic field...Ch. 17 - Name three factors that determine the torque...Ch. 17 - Is the synchronous motor an induction motor?Ch. 17 - What is the amortisseur winding?Ch. 17 - Prob. 9RQCh. 17 - Prob. 10RQ
Ch. 17 - Prob. 11RQCh. 17 - Why can an induction motor never operate at...Ch. 17 - Prob. 13RQCh. 17 - Prob. 14RQCh. 17 - Prob. 15RQCh. 17 - Prob. 16RQCh. 17 - Prob. 17RQCh. 17 - Prob. 18RQCh. 17 - Prob. 19RQCh. 17 - Prob. 20RQCh. 17 - How is the speed of a consequent pole...Ch. 17 - A three-phase squirrel-cage motor is connected to...
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