SUMMARY REVIEW OF Sections 19-25 [AC/DC Motors, Controls, and Maintenance]

GOAL

• To provide the student with an opportunity to evaluate the knowledge and understanding acquired in the study of the previous seven sections.

1. List four applications of 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 with 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 rotates 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. Name 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 1 hp or less that is manually started and is within sight of the starter location, if the distance is no greater than 50 ft, is considered protected from overload by the _____.

d. A motor of 1 hp or less that is manually operated but is more than 50 ft from the starter location shall have a .

e. Where separate overload devices are required for motors, they shall not be set at more than __ % 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 % 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?

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 overload protection to use with this motor. _____

24. What size of 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, DC series motor will not operate satisfactorily on an AC power source.

a. true

b. false