Summary of Units 11-14

OBJECTIVE

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

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

1. The main three-phase leads from a high-voltage alternator usually feed the main bus bars through a switch, the contacts of which are covered by

2. To minimize the danger to personnel working on the maintenance of high-voltage, three-phase alternators, a ___________ switch is used in the main three-phase output leads.

3. In the event of failure of the dc supply used to control the main switch of a three-phase, high-voltage alternator, a separate do source consisting of________ is used.

4. An indicating lamp is used to indicate that the main switch is closed on a three-phase, high-voltage alternator. This lamp is colored ________

5. A_________ indicating lamp is used to indicate that the main line switch is open.

6. Current is measured in the three-phase leads of a high-voltage alternator by ammeters connected in the output leads of the alternator through the ________________

7. The disconnect switch in the main line of an alternator is opened and closed by an operator using rubber gloves and a ________________.

8. A voltage feedback from the main bus to the output terminals of the alternator can occur through an open oil switch as the oil becomes_________.

9. Voltage measurements are made on high-voltage alternators with voltmeters connected to the line through

10. The regulation of an alternator is influenced by the impedance of its windings and the _____________ of the load circuit.

11. The speed of the prime mover driving an alternator determines the and ________ of the output.

12. The normal voltage regulation of an alternator is least affected by a load with a slightly power factor.

13. The output voltage of alternators is maintained through the use of voltage _____.

14. When paralleling two alternators, the procedure used to bring both machines to the same exact phase relationship is called ________________________________________

15. The paralleling of alternators without a synchroscope is best accomplished with synchronizing lamps using the ____________ method.

16. The voltage output of an alternator is controlled by adjusting the circuit resistance.

17. In a revolving-field alternator, slip rings are used to conduct current to the _________ circuit.

18. A dc generator mounted on the same shaft as the alternator is referred to as the ____

19. At a fixed speed of rotation, the frequency of the output voltage depends on the number of ______.

20. Alternator field windings are marked with the letters_________ and ____________.

21. The extent to which voltage output decreases with increases in load current is referred to as voltage.

22. The three-phase windings and the laminated core of a three-phase alternator of the rotating-field type are known as the _______________.

23. An alternator with four field poles is to generate power at 60 hertz. For this frequency the speed must be __________ rev/min.

24. An increase in the field current of an alternator increases its output voltage to an extent determined by field_____ .

25. The regulation of an alternator is poorest when the load circuit has a low, _______ power factor.

26. A UPS system is used to supply consistent power and consists of a _____________ storage system, a charger, and an inverter system.

B. Select the correct answer for each of the following statements.

1. When removing the load from an alternator, the _________

a. oil switch should be opened.

b. disconnect switch should be opened first.

c. machine should be slowed.

d. machine should be stopped.

2. Current to the ammeters on an alternator installation switchboard is never in excess of

a. 100 amperes.

b. 2,400 volts.

c. 50 amperes.

d. 5 amperes.

3. A main disconnect switch is used to

a. remove the load from the alternator.

b. disconnect the oil switch and alternator from the energized bus bar.

c. energize the bus bar.

d. energize the oil switch and alternator.

4. Alternator installation switchboard voltmeters are connected to a. potential transformers.

b. current transformers.

c. the hot bus bar.

d. the oil switch.

5. An oil switch is used to

a. remove the disconnect switch from the line.

b. energize the alternator.

c. interrupt high voltages and currents.

d. lubricate the disconnect switch.

6. When using a synchroscope to parallel alternators, the switches are closed when the indicator is

a. revolving clockwise.

b. revolving counterclockwise.

c. pointing straight up.

d. oscillating.

7. Adjusting the speed of the prime mover of an alternator causes a change primarily in the

a. voltage.

b. frequency.

c. phase polarity.

d. phase poles.

8. The voltage output of an alternator should be increased or decreased by

a. adjusting the field rheostat.

b. adjusting the speed.

c. changing the number of poles.

d. changing the capacities.

9. In an automatic transfer switch, the purpose of the time delay relay is to

a. allow the engine-driven generator to pick up speed.

b. permit the load to increase.

c. delay the normal power supply until it's firmly established.

d. delay the emergency power supply until it's firmly established.