Chapter 9 Review Questions

Chapter 9 Review Questions
1. What is magnetism?
2. Torque is ________.
3. A magnetic field is _________.
4. True or False: A permanent magnet is a piece of material that has been magnetized and can hold its magnetic strength for a reasonable length of time. 5. How is an electromagnet produced?
6. Which of the following produces the best electromagnet?
7. Unlike poles of a magnet _________each other and like poles_________ each other. 8. What part does polarity play in the operation of an electric motor? 9. What part of a motor produces an inductive magnetic field within itself to facilitate the rotating motion? 10.

What part does the frequency of alternating current play in the operation of an electric motor? 11. What would be the speed of a two pole motor operating on a 120 Volts 60 Hz power supply? 12. What are the five types of single phase motors used in the industry? 13. Which of the following correctly lists the motor’s starting torque from lowest to highest? 14. Which of the following is a common use of a shaded-pole motor? 15.

How does a shaded-pole motor operate?

16. How can a shaded-pole motor be reversed?
17. What determines the rotation of a shaded-pole motor?
18. Draw a diagram of a three-speed, shaded-pole motor.

19. What enables a split-phase motor to develop enough torque to begin rotation? 20. What removes the starting winding from the electrical circuit of an open type split phase motor once it reaches 75% of its operating speed? 21. What are the three probable areas of trouble in a split-phase motor? 22. What is the unit of measurement for the strength of a capacitor? 23.

What is the purpose of a capacitor?

24. What is the difference between a running and a running and a starting capacitor? 25. List the five capacitor replacement rules.
26. Explain the operation of a permanent split-capacitor motor. 27. How are a PSC motor and a capacitor start capacitor-run motor similar? 28. What are the advantages and disadvantages of using the following types of motors?
29. What are the similarities between an open-type split-phase motor and a capacitor-start motor? 30. Which of the following is an advantage in using a three-phase motor? 31. Draw a wiring diagram of a capacitor start-capacitor-run motor. 32. True or False: All starting apparatuses are mounted externally to the hermetic compressor shell. 33. What is the process in troubleshooting any electric motor? 34. Which of the following is the capacitance of an 88 uF and a 108 uF starting capacitor connected in series? 35. Which of the following is the capacitance of two 20 uF running capacitors connected in parallel? 36. If a capacitor produces 15A on a 240 volt supply, which of the following is its microfarad rating? 37. Which of the following capacitors could be used to replace a 35 uF, 370 running capacitor? 38. Which of the following capacitors could be used to replace a 188 uF, 250 V starting capacitor? 39. Which of the following capacitors or combination of capacitors could be used to replace a 45 uF, 370 V running capacitor? 40. Which of the following capacitors or combination of capacitors could be used to replace an 88 uF, 250 V starting capacitor? 41. Find the common, start, and run terminals of the following hermetic compressors. A.

B.
C.
42. Briefly explain the procedure for troubleshooting hermetic compressor motors. 43. What are the electrical failure categories for hermetic compressor motors? 44. What precautions should be taken when checking hermetic compressor motors? 45. What would be the highest allowable resistance reading for a grounded compressor motor? 46. What are the advantages of using an electronically commutated motor over a PSC motor? 47. Explain the construction of an ECM.

48. An ECM is a ______________.
49. True or False: The resistance readings of the windings of a properly operating ECM should be equal. 50. True or False: The line voltage power supply of an ECM should be disconnected or connected with the power on.