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FREE AND STUDY GAMES ABOUT AC THEORY CH 31 EXAM
QUESTIONS
Qs and Ans Expert- Explanation
This Exam contains:
-Guarantee passing score -29 Questions and Answers -format set of multiple-choice -Expert- Explanation Question 1: 28. Using the "Three Lamp" method, houw do yu know when the two alternators are in-phase with each other?
Answer:
all the lights are out
Question 2: 1. Another name for an AC generator is the ___
Answer:
alternator Question 3: 17. Large-capacity generators are often enclosed in a ___ atmosphere for cooling purposes
Answer:
hydrogen Question 4: 24. What three factors determine the output voltage of an alternator?
Answer:
length of conductors, speed of rotation, strength if magnetic field.
Question 5: 23. A generator has four poles and a speed of 1,500 RPM. what is the output frequency?
Answer:
50 Hz
5- = (4 * 1,500) / 120
Question 6: 14. A rotating exciter mounted on the same shaft as the main generator is usually called a ___exciter
Answer:
brushless Question 7: 9. When the armature is held stationary in a generator it is called the ___
Answer:
stator
Question 8: 8. The ___ is the rotating member of a generator or motor.
Answer:
rotor Question 9: 10. Two tpes of rotating field construction are the ___ rotor and the ___ rotor
Answer:
salient pole, round rotor Question 10: 19. What are the factors that determine the frequency of an alternator?
Answer:
number of poles, speed of rotor Question 11: 2. What is the primary difference between a simple DC generator and a simple AC generator
Answer:
Dc uses a comutator AC uses slip rings and brushes
Question 12: 29. Another method of paralleling two alternator is with the use of a
Answer:
synchroscope Question 13: 7.What is the advantae of using a rotating field and a stationary armature on commercial generators
Answer:
design permits higher kva ratings because he output of circuit is connected to the stator. page 240 Question 14: 11. Pole faces that jut out and are ery pronounced are called ___ poles.
Answer:
salient poles
Question 15: 18. Which dissipates heat faster, hydrogen or air?
Answer:
hydrogen Question 16: 26. What three conditions must be met when connection two 3-phase alternators in parallel?
Answer:
1) ?
2) outputs must be same frequency
3) all output kVa must be same Question 17: 27. The most common method of detecting when the direction of the magnetic field of one alternator is matched with the phase rotation of a paralleled alternator is with the use of ___
Answer:
- lights
Question 18: 25. How is the output voltage controlled?
Answer:
increasing or decreasing strength of magnetic field.
Question 19: 15. Alternators wiht small kVa ratings are usually ___ cooled
Answer:
Air Question 20: 22. How many poles are required for a generator to hae a frequecy of 60 Hz at 1,200 RPM?
Answer:
P = 6
60 = ( 1,200 * P / 120)
Question 21: 3. There are two basic types of altenator. These are the revolving ___ type and the revolving ___ type
Answer:
Armature Field Question 22: 4. Slip rings, unlike the segmented commutator, are contructed as a ___ ring, with each end of the armature loop connected to a seperate ___
Answer:
continuous, ring Question 23: 21. To generate 50 Hz with an 8-pole generator, the speed of rotation must be
___RPM
Answer:
750 RPM
Question 24: 16. Air cooled alternator usually have a ___ attached to one end of the rotor to help circulate air.
Answer:
fan Question 25: 5. In a 3-phase generator, the three sets of windings are placed ___ apart.
Answer:
120 degrees
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