homework questions
1. If an alternator is being driven by a gasoline engine, how is the speed of the alternator’s rotor
controlled?
A. By electronic controls C. By an exciter
B. By a governor D. By an amortisseur coil
2. What is the maximum temperature rating of Class F insulation?
A. 105° C C. 155° C
B. 130° C D. 180° C
3. How are series-connected alternators set up so that they run in synchronization?
A. They’re mechanically coupled. C. They run from a single exciter.
B. They’re cross-phase connected. D. They use reaction-type rotor fields.
Examination 43
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08601200
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4. Which one of the following views shows the point where the coil cuts the minimum amount of flux?
5. A standard alternator would have ratings of
A. 500 kW and 500 V. C. 2250 kW and 3000 V.
B. 750 kW and 575 V. D. 10,000 kW and 13,800 V.
6. What is the maximum cooling air temperature allowed for in the design of an alternator?
A. 20° C C. 60° C
B. 40° C D. 80° C
7. A two-pole turbogenerator is designed for 60 Hz operation. What is the highest speed that would be
used to turn this steam-turbine alternator?
A. 600 rpm C. 2400 rpm
B. 1200 rpm D. 3600 rpm
8. The damper windings of an alternator are normally carried on the
A. armature. C. rotor.
B. prime mover. D. stator.
9. You want to make sure that two alternators are operating properly in parallel. Which of the following
readings should be the same for each of the two machines?
A. Wattmeter readings C. Current readings
B. Power-factor readings D. True power readings
10. How can the voltage at the terminals of an alternator be doubled?
A. By cutting the strength of the magnetic field in half
B. By doubling the turns of wire in the coils
C. By cutting the speed of the machine in half
D. By doubling the size of the coil wires
44 Examination
11. For the alternator part shown below, the electromagnets get a direct current from
A. a ballast ring. C. an impulse turbine.
B. a yoke. D. an exciter.
12. A 36-pole alternator will generate how many cycles of AC voltage during one revolution of the
alternator?
A. 6 C. 18
B. 9 D. 36
13. A single alternator isn’t operating properly. Your first step in shutting down this single alternator is to
A. shut down the prime mover. C. open all of the feeder switches.
B. reduce the output voltage of the alternator. D. open the field switch of the alternator.
14. What is the typical rating of exciter voltage?
A. 25 V C. 125 V
B. 50 V D. 400 V
15. What type of rotors will an engine alternator usually have?
A. Salient-pole rotors with horizontal shafts C. Cylindrical rotors with horizontal shafts
B. Salient-pole rotors with vertical shafts D. Cylindrical rotors with vertical shafts
16. Which one of the following voltages is not a typical alternator voltage?
A. 125 VAC C. 4300 VAC
B. 460 VAC D. 13,800 VAC
17. What is an infinite system?
A. An infinite system is one that isn’t connected to a load.
B. An infinite system is one that relies on all alternators to produce the proper voltage and current.
C. An infinite system is one that transmits power over a large network.
D. An infinite system is one that doesn’t rely on the operation of a single alternator.
Examination 45
18. A static exciter unit will use what type of device to provide DC current to the field windings?
A. Semiconductor rectifier C. Static straps
B. A motor-generator set D. A direct-coupled generator
19. In a two-pole alternator, one cycle of AC power will equal how many electrical degrees?
A. 90° C. 270°
B. 180° D. 360°
20. In a three-phase or polyphase alternator, how are the coils spaced?
A. 90° apart C. 150° apart
B. 120° apart D. 180° apart
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