Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Textbook Question
Chapter 36, Problem 4RQ
What solid-state device is generally used to produce variable frequency in drives designed to control motors up to 500 HP?
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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…
Assume that you are to design a 3V V-belt drive. Given that input speed as 1750 rpm and nominal output speed as 725 rpm. Starting with belt linear velocity 4000 ft/min, specify the output sheeve D2 once you specify D1 from last question.
D2 = ___ in.
Provide write down steps including equations.
Assume that you are to design a 3V V-belt drive. Given that input speed as 1750 rpm and nominal output speed as 725 rpm. Starting with belt linear velocity 4000 ft/min, specify the input sheeve D1 from the list above.
D1 = ___ in.
Provide write down steps including equations.
*** 8.73 and 8.9 were marked incorrect
Chapter 36 Solutions
Understanding Motor Controls
Ch. 36 - Prob. 1RQCh. 36 - Prob. 2RQCh. 36 - If an alternator is used to provide variable...Ch. 36 - What solid-state device is generally used to...Ch. 36 - Why are SCRs used to construct a bridge rectifier...Ch. 36 - What is the main disadvantage of using SCRs in a...Ch. 36 - How are junction transistors driven into...Ch. 36 - What is the disadvantage of driving a junction...Ch. 36 - Prob. 9RQCh. 36 - In variable frequency drives that employ IGBTs,...
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