SUMMARY REVIEW OF Sections 5-10 [AC/DC Motors, Controls, and Maintenance]

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GOAL

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

A. Complete the following statements:

1. A DC motor starter is designed to limit the ____.

2. A three-terminal starting rheostat provides __ protection for a shunt motor.

3. Because the holding coil of a four-terminal rheostat is connected across the source, this type of rheostat provides __ protection to a motor.

4. A drum controller is used when the operator has __ control of the motor.

B. Select the correct answer for items 5 through 13, and place the corresponding letter in the space provided.

5. Interpretation of automatic circuits requires the recognition of ____

a. color.

c. parallel circuits.

b. rating.

d. electrical circuit symbols.

6. A piece of apparatus that contains a minimum of one set of contacts operated by a coil is called a _

a. motor.

c. relay.

b. magnet.

d. dynamo.

7. Normally closed contacts are

a. open at all times.

b. open when the relay coil is de-energized.

c. open when the relay coil is energized.

d. closed when the relay coil is energized.

8. A schematic automatic motor controller circuit diagram shows the _

a. actual wiring layout.

b. schematic motor diagram.

c. actual sequence of operations of the entire circuit.

d. sequence of operations of the starting circuit only.

9. One type of automatic controller operates on the basis that the CEMF generated in a motor __

a. increases the starting current.

b. energizes a starting relay.

c. de-energizes a starting relay.

d. reduces the field current.

10. Another type of controller accelerates the motor in steps by _____

a. using a series of thermal elements.

b. allowing starting resistor voltage drops to energize relays.

c. operation of relays controlled by speed.

d. cam-controlled relays.

11. A remote-controlled motor reversal requires ___

a. one relay with two contacts.

b. two single contactor relays.

c. two double contactor relays.

d. two interlocked relays.

12. The principle of dynamic braking involves ____

a. the use of a dynamo as a brake.

b. the use of an electromagnetic brake connected across the motor armature.

c. connecting a low resistance across the motor armature.

d. connecting a brake relay across the armature.

13. SCADA refers to a system that

a. scans and records information.

b. supervises control and data acquisition.

c. is a protocol for machine interaction.

d. operates to provide safety for machinery.

14. When humans need to interface with an automated machinery control, a typical method would be to use ___

a. a microcontroller.

b. multiple-screen PCs.

c. an HMI.

d. an MHI.

C. Complete the statements in items 15 through 19 by selecting the letter of the appropriate phrase or phrases from the list below right. Write the letter(s) in the space provided.

15. Undervoltage protection is provided in _____.

16. Dynamic braking is used for _____.

17. Multiple-step acceleration is used for starting _.

18. Automatic starters provide more uniform acceleration than __.

19. A sealing circuit is used in _.

a. quick stopping

b. large motors

c. a three-terminal starting rheostat

d. a four-terminal starting rheostat

e. small motors

f. series motors

g. manual starters

h. control circuits

20. Match each of the following symbols with its description at the right. Place the letter of the symbol in the space provided.


a.

b.

c.

d.

e.

f.

g.

1. __ Normally closed pushbutton

2. __ Thermal motor overload relay

3. __ Shunt relay coil

4. __ Normally open contact

5. __ Fuse

6. __ Normally closed contact

7. __ Normally open pushbutton

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