Summary of Units 20-26

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OBJECTIVES:

To give the learner an opportunity to evaluate the knowledge and understanding acquired in the study of the previous seven units.

1. List four applications for selsyn units.

a.

b.

c.

d.

2. Draw a schematic wiring diagram of a selsyn system consisting of a transmitter and one selsyn receiver unit.

3. Explain the operation of a simple selsyn system consisting of one transmitter and one selsyn receiver unit. _____.

4. Explain the purpose of a differential selsyn unit.

5. Draw a schematic wiring diagram of a selsyn system having one selsyn exciter unit, a differential selsyn unit, and one selsyn receiver unit.

6. Insert the correct word or phrase to complete each of the following statements.

a. Whenever the rotor of the ____ is out of alignment with the rotor of the receiver selsyn, currents are present in the stator windings.

b. A selsyn receiver will rotate continuously if the transmitter rotor is driven at speed.

c. The rotor units of the transmitter and receiver selsyns must be excited from the same

d. The use of a mechanical damper on the rotor of selsyn receivers minimizes any tendency of the receiver to ________

7. List four applications for a split-phase induction motor.

a.

b.

c.

d.

8. What are the basic parts of a split-phase induction motor? _________

9. Explain how the direction of rotation of a split-phase induction motor is reversed.

10. What happens if the centrifugal switch contacts fail to reclose when a split-phase motor is stopped?

11. A split-phase induction motor has a dual-voltage rating of 115/230 volts. The motor has two running windings, each of which is rated at 115 volts. The motor also has two starting windings, each of which is rated at 115 volts. Draw a schematic connection diagram of this split-phase induction motor connected for 230 volts.

12. What is the basic difference between a split-phase induction motor and a capacitor start, induction run motor? _________

13. If the centrifugal switch fails to open as a split-phase motor accelerates to the rated speed, what happens to the starting winding?

14. If the centrifugal switch on a capacitor start, induction run motor fails to open as the motor accelerates to the rated speed, what may happen in the starting winding circuit?

15. What is one limitation of a capacitor start, induction run motor? _________

16. What is the basic difference between a capacitor start, induction run motor and a capacitor start, capacitor run motor? ____________

17. List three types of capacitor start, capacitor run motors.

a.

b.

c.

18. Insert the correct word or phrase to complete each of the following statements.

a. The capacitor in series with the starting winding of a capacitor start, induction run motor improves the _________ torque of the motor.

b. A split-phase induction motor has good speed regulation but ____________ starting torque characteristics.

c. A capacitor start, capacitor run motor has practically power factor when operating at full load.

d. A capacitor start, capacitor run motor has ______ starting torque and ________ speed regulation.

e. A capacitor start, induction run motor has _______ speed regulation.

19. Insert the correct word or phrase to complete each of the following statements.

a. The capacitor used with a capacitor start, induction run motor is used only for the purpose of improving the _______ of the motor.

b. The capacitors used with a capacitor start, capacitor run motor are used to improve ___

c. A motor of one horsepower or less which is manually started and which is within sight of the starter location, provided the distance is no greater than 50 feet, is considered protected by the _______.

d. A motor of one horsepower or less which is manually operated but more than 50 feet from the starter location shall have a _________

e. Where separate overcurrent devices are required for motors, they shall not be set at more than ________percent of the motor nameplate full-load current rating for motors marked to have a temperature rise not over __________ for motors with a marked service factor of 1.15, and at not more than ___________ percent for all other types of motors.

20. Where is a repulsion motor used? _________

21. What are the two types of repulsion start, induction run motors?

a.

b.

22. Where are repulsion start, induction run motors used?

23. A 3-hp, 230-volt, 17-ampere, single-phase repulsion start, induction run motor is connected directly across rated line voltage.

a. Determine the overcurrent protection for the branch circuit feeding this motor.

b. Determine the running overcurrent protection to use with this motor.

24. What size copper wire (Type THHN) is used for the branch circuit feeding the motor in question 23?

25. What is a repulsion-induction motor?

26. What is one advantage to the use of the repulsion-induction motor as compared with the repulsion start, induction run motor?______

27. Insert the correct word or phrase to complete each of the following statements.

a. A repulsion motor has good _______________ but poor

b. The speed of a repulsion motor can be controlled by changing the ____________

c. Both the brush-riding and the brush-lifting types of repulsion start, induction after they have run motors operate as __________ after they have accelerated to rated speed.

d. The repulsion-induction motor has good _______ and relatively good

28. Explain how the direction of rotation is changed on any one of the three types of single-phase repulsion motors.________

29. What is a universal motor? _________

30. Draw a schematic diagram of a conductively compensated series motor.

31. Draw a schematic diagram of an inductively compensated series motor.

32. In what way is an inductively compensated series motor different from a conductively compensated series motor? _____________

33. Explain how the direction of rotation is reversed for a conductively compensated series motor.

34. What is the purpose of a compensating winding in an ac series motor? __________

35. A universal motor can be operated on

a. ac power only.

b. dc power only.

c. ac or dc power.

36. A conductively compensated series motor can be operated on

a. ac power only.

b. dc power only.

c. ac or dc power.

37. An inductively compensated series motor can be operated on either ac or dc power.

a. true b. false

38. A large 25-hp, direct-current series motor won't operate satisfactorily on an ac power source.

a. true b. false

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