Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Chapter 42, Problem 11RQ
To determine
The percentage of voltage unbalance.
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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…
Q A motor of 15 horsepower, has a code letter L, and is operated on a 400-volt line. Find the locked rotor current
Question 2
Beli vifth
Slack side
Motor
(imprut)
Tight side
Beli thickpess\
Centre distance
Figure 2
Figure 2 shows an open flat belt drive connected to a motor and a pulley. The
motor transmits 20 kw to the connect pulley of 450 mm diameter and is rotating
at 850 r/min to a second pulley rotating at 400 r/min. The distance between
pulley centres is approximately 2 m. The belt is 6 mm thick and has a density of
970 kg/m. The maximum stress in the belt is not to exceed 2,7 MPa. The
coefficient of friction for both pulleys is 0,3.
Determine:
2.1. The diameter of the second pulley.
2.2. The length of the belt.
3.3. The width of the belt taking centrifugal tension into account.
Chapter 42 Solutions
Understanding Motor Controls
Ch. 42 - What are the three main electrical test...Ch. 42 - What is the advantage of a plunger type voltage...Ch. 42 - A motor is tripping out on overload. The motor...Ch. 42 - A motor is tripping out on overload. The motor...Ch. 42 - Prob. 5RQCh. 42 - Refer to the circuit shown in Figure 42–17. Assume...Ch. 42 - Prob. 7RQCh. 42 - Refer to the circuit shown in Figure 4221. Assume...Ch. 42 - Prob. 9RQCh. 42 - Refer to the circuit shown in Figure 42–21. Assume...
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- What is the function of the compensating winding?arrow_forwardWhen a repulsion-start induction-run motor reaches about 75% of rated full-load speed, it stops operating as a repulsion motor and starts operating as a squirrel-cage motor. What must be done to cause the motor to begin operating as a squirrel-cage motor?arrow_forwardA 75-hp, three-phase squirrel-cage induction motor is connected to 480 volts. The motor has a NEMA code D. What is the starting current for this motor?arrow_forward
- q16 The statement is True or False?arrow_forwardThe reason why the starting torque of a series motor is higher than a shunt motor is because the series motor has O more current flowing through its armature O a stronger net magnetic field around both coils during the inrush of stator currentarrow_forwardA 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?arrow_forward
- please answer quickly!!arrow_forwardWhat is the minimum pulley diameter for a 1 HP motor running at 1750 RPM?arrow_forwardThere is a 3 HP, 220 Vrms single - phase induction motor that operates with a 0.85 lagging power factor and 80 9% efficiency. What is the magnitude of the RMS motor current? O 75 Amps 15 Amps O 5 Amps O 3 Ampsarrow_forward
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