Electrical Transformers and Rotating Machines
4th Edition
ISBN: 9781305494817
Author: Stephen L. Herman
Publisher: Cengage Learning
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Question
Chapter 19, Problem 7RQ
To determine
The type of connection of the nine-lead three-phase motor when it is found that the continuity exist between T7, T8, and T9.
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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…
QUESTION 1
Consider the equations of motion of an armature controlled DC motor given by
Jw(t)+bw (t) Ki (t)
=
di (l)
L + Ri (t) + Kw (t)
=
-Tfriction - Tload (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).
When the input voltage and torque are constant, the transient response of this system has the form of the homogeneous solution.
What is the time constant of the transient response? Find the characteristic roots of this system first. Keep 3 significant figures, and do not include units. Use scientific
notation.
The constants are given below:
Nominal voltage, Vin(t) = 17 V
Moment of inertia of the rotor, J = 0.02 kg-m²
Motor viscous friction constant, b = 0.009 N-m-s
Friction torque, Tfric = 0.003 N-m
Armature inductance, L = 0.1 H
Armature resistance, R = 0.35
Back emf constant and motor torque constant, K = 0.21 N-m/A.
**Recall that the time constant (or relaxation time) is…
In speed coontrol of dc motor, the potentiometer is used as a control element.
Select one:
True
False
Chapter 19 Solutions
Electrical Transformers and Rotating Machines
Ch. 19 - Why is it necessary to keep lubrication records...Ch. 19 - Why is it necessary to pick between the commutator...Ch. 19 - What are the effects of improper brush tension in...Ch. 19 - What instrument is used to test the insulation of...Ch. 19 - How do you check for an open armature winding?
Ch. 19 - What instrument is generally used to test an...Ch. 19 - Prob. 7RQCh. 19 - Prob. 8RQCh. 19 - Prob. 9RQCh. 19 - Assume that a nine-lead dual-voltage motor is...
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