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Mr. Gregory White
Mr. Gregory White, Professor
Category: Homework
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Experience:  M.A., M.S. Education / Educational Administration
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Questions 1w25: Select the one best answer to each question.
L A series d-c motor is most likely to be used on a
A. hoist. C. compressor.
B. blower. D. woodworking machine.
2. If the speed of a centrifugal pump is reduced to one-half the original
value, the power will be reduced to
A. one-sixteenth. C. one-quarter.
B. one-eighth. D. one-half.
3. What type of squirrel-cage motor is ordinarily used with small air
compressors equipped with a relief valve?
A. Design D motor C. Design B motor
B. Design C motor D. Design A motor
4. The power factor of a plant may be improved by" installing
A. d-c motors. C. wound-rotor motors.
B. synchronous motors. D. squirrel-cage motors.
5. The force required to bring an object weighing 65 lb from rest to a
speed of 50 ips in 10 sec is approximately
A. 1 lb. C. 10 lb.
B. 5 lb. D. 50 lb.
6. When the number of poles in a squirrel-cage motor is changed from
4 to 8, the speed is
A. doubled. C. reduced by half.
B. not changed. D. increased four times.
7. The maximum torque a motor can produce is called the
A. breakdown torque. C. full-load torque.
B. saturation torque. D. locked-rotor torque.
S. The most economical voltage for a lS0-hp a-c motor is
A. 800 volts. C. 440 volts.
B. 600 volts. D. 220 volts.
9. When minimum space is an important requirement, the best type of
mechanical connecting device for slow-speed conveyors is a
A. coupling. C. Rat belt.
B. gearmotor. D. speed reducer.
2 INDUSTRIAL MOTOR ApPLICATIONS
A certain pump is capable of delivering 625 gpm, efficiency is rated
at 750/0, and the sum of the static and friction heads is 2 ft. What is
the horsepower of this pump?
A 0.417
B. 0.589
C. 4.17
D.5.89
lL Why are wound-rotor motors successful in controlling the speed of
printing-press drives?
A. The press runs for long periods without showing the effects of load
variations.
B. The operating speed of the press is normally below 700/0 synchronous
speed.
C. Few steps of rotor resistance are used, which allows for instant acceleration.
D. The shared load is large and does not change rapidly.
12. Regenerative braking is used on induction motors to
A. mcrease the speed above synchronous speed.
B. decrease the speed below synchronous speed.
C. increase the actual speed to the value of synchronous speed.
D. decrease the actual speed to the value of synchronous speed.
13. An a-c hoist motor has the following duty cycle: acceleration, no
amp for S sec; constant speed, 60 amp for IS sec; lowering and
braking, 20 amp for 10 sec; and rest, 0 amp for 5 sec. The current
rating for this motor is
A. 69.64 amp. C. 76.56 amp.
B. 74.09 amp. D. 78.29 amp.
14. A 40-hp 4S0-rpm motor drives an SOO-lb flywheel which is 4 ft in
diameter. The flywheel is to be brought from rest to a speed of
480 rpm. If the motor is controlled so that it maintains its torque at
1000/0, how long will it take the motor and the flywheel to reach
480 rpm?
A. 2.9 sec. C. 5.7 sec.
B. 4.4 sec. D. 8.1 sec.
15. To prevent the motor speed from increasing until the motor fails
mechanically, a load should always be connected to a
A series d-c motor. C. wound-rotor motor.
B. shunt d-c motor. D. synchronous motor.
16. Which one of the following devices would be used in an application
requiring large volumes of air at a pressure of 8 oz per sq in.?
A. Disk fan C. Propeller fan
B. Rotary blower D. Centrifugal fan
17. The type of braking method useful only as a means of lowering
loads is
A. plugging. C. magnetic braking.
B. regenerative braking. D. dynamic braking.
INDUSTRIAL MOTOR AI'I'LICA nONS
18. If a gear unit is used with an a-c motor to increase the speed by
a ratio of 4 to 1, then the torque applied to the system is
A. increased by 2 to 1. C. decreased by 2 to 1.
E. increased by 4 to L D. decreased by 4 to 1.
19. When the speed of a machine is the same as that of the driving
motor, the easiest method of connecting the machine and the motor
is with
A. belts. C. chains.
£. gears. D. coupling.
20. Which one of the following squirrel-cage motors is best suited to
produce high starting torque at low starting current and low slip?
A. Design D C. Design B
B. Design CD. Design A
21. A two-stage compressor with a capacity of 1000 dm compresses 100
cu ft of free air per minute to a pressure of 100 psi. What is the
required bhp?
A. 18 C. 8
B. 14 D. 4
22. .A centrifugal fan running at 100 rpm delivers air at the rate of 6000
dm at a pressure of 1 oz per sq in. and requires 2 hp. At 300 rpm it
delivers 18,000 cu ft of air per minute. What is the horsepower
required?
A. 9 C. 27'
B. 18 D. 54
23. What type of drive is needed for a vertical lift bridge using two
induction motors to operate the two ends of the bridge at the same
time?
A. Adjustable voltage drive C. Synchrotlc drive
B. Adjustable frequency drive D. Eddy-current coupling
Submitted: 1 year ago.
Category: Homework
Expert:  Mr. Gregory White replied 1 year ago.

Hello, my name is Greg.

I see this might be time sensitive.

Do you still need this answered?

Customer: replied 1 year ago.
dont need right away but sooner the better
Expert:  Mr. Gregory White replied 1 year ago.
THIS ANSWER IS LOCKED!

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