5. The force required to bring an object weighing 65 lb from rest to a speed of 50 fps in 10 sec is approximately

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Bathsheba Robertson
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1 Student ID: Exam: 4341RR - Industrial Motor Applications When you have completed your exam and reviewed your answers, click Submit Exam. Answers will not be recorded until you hit Submit Exam. If you need to exit before completing the exam, click Cancel Exam. Questions 1 to 25: Select the best answer to each question. Note that a question and its answers may be split across a page break, so be sure that you have seen the entire question and all the answers before choosing an answer. 1. The most economical voltage for a 150-hp a-c motor is A. 440 volts. B. 800 volts. C. 220 volts. D. 600 volts. 2. When minimum space is an important requirement, the best type of mechanical connecting device for slow-speed conveyors is a A. gearmotor. B. speed reducer. C. coupling. D. flat belt 3. 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. Propeller fan B. Disk fan C. Rotary blower D. Centrifugal fan 4. 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 B. Design B C. Design A D. Design C 5. The force required to bring an object weighing 65 lb from rest to a speed of 50 fps in 10 sec is approximately A. 10 lb. B. 50 lb. C. 1 lb. D. 5 lb.

2 6. When the number of poles in a squirrel-cage motor is changed from 4 to 8, the speed is A. not changed B. doubled C. increased four times. D. reduced by half. 7. The power factor of a plant may be improved by installing A. wound-rotor motors B. synchronous motors C. squirrel-cage motors. D. d-c motors. 8. 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 4 to 1. B. increased by 2 to 1. C. decreased by 2 to 1. D. decreased by 4 to The type of braking method useful only as a means of lowering loads is A. plugging B. magnetic braking. C. regenerative braking. D. dynamic braking. 10. 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 B. 4 C. 8 D A certain pump is capable of delivering 625 gpm, efficiency is rated at 75%, and the sum of the static and friction heads is 2 ft. What is the horsepower of this pump? A B C D An a-c motor operating at a power-line frequency of 60 Hz has a synchronous speed of 900 rpm. The number of poles in this motor i A. 6

3 B. 8 C. 12 D Regenerative braking is used on induction motors to A. increase the speed above synchronous speed B. increase the actual speed to the value of synchronous speed C. decrease the actual speed to the value of synchronous speed. D. decrease the speed below synchronous speed. 14. If an a-c system requires a 250-hp motor to drive a machine at a uniform rate of speed, what type of motor should be used? A. Synchronous motor B. Squirrel-cage motor C. Induction motor D. Wound-rotor motor 15. Why are wound-rotor motors successful in controlling the speed of printing-press drives? A. Few steps of rotor resistance are used, which allows for instant acceleration B. The press runs for long periods without showing the effects of load variations. C. The operating speed of the press is normally below 700/0 synchronous speed D. The shared load is large and does not change rapidly. 16. A series d-c motor is most likely to be used on a A. hoist B. compressor C. blower. D. woodworking machine 17. What type of squirrel-cage motor is ordinarily used with small air compressors equipped with a relief valve? A. Design C motor B. Design D motor C. Design B motor D. Design A motor 18. An a-c hoist motor has the following duty cycle: acceleration, 110 amp for 8 sec; constant speed, 60 amp for 18 sec.; lowering and braking, 20 amp for 10 sec; and the rest, 0 amp for 5 sec. The current rating for this motor is A amp B amp. C amp D amp.

4 25. A 40-hp 480-rpm motor drives an 800-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, 19. If the speed of a centrifugal pump is reduced to one-half the original value, the power will be reduced to A. one-quarter B. one-eighth. C. one-sixteenth. D. one-half. 20. 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. Eddy-current coupling B. Synchrotlc drive C. Adjustable voltage drive D. Adjustable frequency drive 21. 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. B. wound-rotor motor C. shunt d-c motor. D. synchronous motor 22. The maximum torque a motor can produce is called the A. full-load torque. B. breakdown torque. C. locked-rotor torque. D. saturation torque. 23. 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. 18 B. 54 C. 9 D 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. gears. B. coupling. C. belts. D. chains.

5 how long will it take the motor and the flywheel to reach 480 rpm? A. 2.9 sec. B. 8.1 sec. C. 5.7 sec. D. 4.4 sec. End of exam

Pretest Module 21 Units 1-3 AC Generators & Three-Phase Motors

Pretest Module 21 Units 1-3 AC Generators & Three-Phase Motors 1. What are the two main parts of a three-phase 2. Which part of a three-phase squirrel-cage induction motor is a hollow core? 3. What are