Deck 32: Three-Phase Alternators

Question 1

What is one factor that controls the output frequency of an alternator?

A) number of stator poles and rotor rotation speed
B) input voltage
C) number of stator poles and number of rotor bars
D) input voltage and torque

Answer 1

A

Question 2

Using a(n) is one method of preventing induced voltage from becoming excessive.

A) paralleling switch
B) inductive bypass
C) field discharge resistor
D) capacitive resistor

Answer 2

C

Question 3

Power is carried to the outside circuit of a revolving armature type alternator via brushes riding against the .

A) commutators
B) diodes
C) sliprings
D) wires

Answer 3

C

Question 4

By increasing or decreasing the strength of the magnetic field of the rotor, the of an alternator
is controlled.

Question 5

An alternator that has a separate small alternator mounted on the shaft of its rotor is equipped with a(n) .

A) electric starter
B) primary exciter
C) brushless energizer
D) brushless exciter

Question 6

A three-phase alternator containing six poles is turning at 1000 RPM. What is the output frequency?

A) 30 Hz
B) 40 Hz
C) 50 Hz
D) 60 Hz

Question 7

The higher power output alternators use a revolving .

A) armature
B) field
C) stator
D) exciter

Question 8

An alternator containing eight poles per phase is turning at 1500 RPM. What is the output frequency?

A) 70 Hz
B) 80 Hz
C) 90 Hz
D) 100 Hz

Question 9

An alternator containing eight poles per phase is turning at 900 RPM. What is the output frequency?

A) 30 Hz
B) 40 Hz
C) 50 Hz
D) 60 Hz

Question 10

The non-rotating part of a revolving-field-type alternator is called the .

A) stator
B) exciter
C) rotor
D) synchronizer

Question 11

Alternators of small kilovolt-ampere rating are generally _-cooled.

A) liquid
B) air
C) hydrogen
D) nitrogen

Question 12

The direct current that is an input to the alternator's rotor is the current.

A) excitation
B) starting
C) synchronizing
D) initiating

Question 13

If one alternator does not produce sufficient power to supply a load, another alternator can be connected to the circuit. The second alternator is connected in .

A) series
B) parallel

Question 14

alternators have a fan attached to one end of the shaft.

Question 15

In order to increase the efficiency of the cooling, some alternators operate in a(n) atmosphere.

A) helium
B) oxygen
C) hydrogen
D) nitrogen

Question 16

The rotating part of a revolving-armature-type alternator is called the .

A) stator
B) exciter
C) rotor
D) synchronizer

Question 17

What machines operate on the same principle of electromagnetic induction as DC generators, but they have no commutator?

A) alternators
B) transformers
C) oscillators
D) converters

Question 18

The revolving armature type alternator is capable of power output and is, therefore, often used than the revolving field type.

A) less; more
B) less; less
C) more; less
D) more; more

Question 19

The direction of magnetic field rotation is known as

A) phase
B) loop

Question 20

A(n) is used to measure the difference in voltage and frequency between two alternators.

A) synchronoscope
B) ohmmeter
C) voltmeter
D) diode