Question 1

The higher power output alternators use a revolving _____.&#10;A) armature&#10;B) field&#10;C) stator&#10;D) exciter

Accepted Answer

Higher power output alternators use a revolving field rather than a revolving armature. This design allows for the stationary part (stator) to handle the high power output, while the field rotates.

Question 2

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 _____.&#10;A) series&#10;B) parallel

Accepted Answer

When connecting multiple generators to a circuit, it is best to connect them in parallel so that they can share the load. Connecting them in series would increase the voltage, but not the current, which would not be useful for supplying a load.

Question 3

In order to increase the efficiency of the cooling, some alternators operate in a(n) _____ atmosphere.&#10;A) helium&#10;B) oxygen&#10;C) hydrogen&#10;D) nitrogen

Accepted Answer

Hydrogen has a higher thermal conductivity than other gases, allowing for more efficient cooling.

Question 4

Alternators of small kilovolt-ampere&#160;rating are generally _____ -cooled.&#10;A) liquid&#10;B) air&#10;C) hydrogen&#10;D) nitrogen

Accepted Answer

Alternators of small kilovolt-ampere rating are generally air-cooled. Air-cooled alternators use air as the cooling medium, which is circulated over the stator and rotor through appropriate ducts or passages. Liquid-cooled alternators, on the other hand, use water or oil as the cooling medium. Hydrogen and nitrogen-cooled alternators are typically used for high voltage applications, such as in power plants or for large industrial motors.

Question 5

A three-phase alternator containing six poles is turning at 1000 RPM. What is the output frequency?&#10;A) 30 Hz&#10;B) 40 Hz&#10;C) 50 Hz&#10;D) 60 Hz

Accepted Answer

The output frequency (f) of an alternator is given by the formula f = (P*N)/120, where P is the number of poles and N is the rotational speed in RPM. Plugging in the values, we get f = (6*1000)/120 = 50 Hz. Therefore, the output frequency of the alternator is 50 Hz.

Question 6

The direction of magnetic field rotation is known as _____ rotation.&#10;A) phase&#10;B) loop

Accepted Answer

The direction of magnetic field rotation is referred to as phase rotation. Loop rotation is not a common term used in relation to magnetic fields.

Question 7

The direct current that is an input to the alternator's rotor is the _____ current.&#10;A) excitation&#10;B) starting&#10;C) synchronizing&#10;D) initiating

Accepted Answer

The direct current input to the alternator's rotor is known as excitation current. This current generates a magnetic field in the rotor that interacts with the stator windings and produces an alternating current output. Starting current refers to the current required to start the engine, synchronizing current is used to match the voltage and frequency of the alternator to the power grid, and initiating current is not a commonly used term in relation to alternators.

Question 8

The non-rotating part of a revolving-field-type&#160;alternator is called the _____.&#10;A) stator&#10;B) exciter&#10;C) rotor&#10;D) synchronizer

Accepted Answer

The non-rotating part of a revolving-field-type alternator is called the stator. The stator provides a stationary magnetic field that interacts with the rotating magnetic field produced by the rotor, thereby inducing an electrical current in the stator windings.

Question 9

The rotating part of a revolving-armature-type&#160;alternator is called the _____.&#10;A) stator&#10;B) exciter&#10;C) rotor&#10;D) synchronizer

Accepted Answer

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

Question 10

A(n) _____ is used to measure the difference in voltage and frequency between two alternators.&#10;A) synchronoscope&#10;B) ohmmeter&#10;C) voltmeter&#10;D) diode

Accepted Answer

A synchronoscope is specifically designed to measure the difference in voltage and frequency between two alternators, while an ohmmeter is used to measure resistance, a voltmeter is used to measure voltage, and a diode is used as a semiconductor device to convert AC to DC or to modulate signals.

Question 11

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

Accepted Answer

The answer of _______________ alternators have a fan attached to...

Question 12

By increasing or decreasing the strength of the&#160;magnetic field of the rotor, the _______________ of an alternator is controlled .

Accepted Answer

The answer of By increasing or decreasing the strength of...

Question 13

An alternator that has a separate small alternator mounted on the shaft of its rotor is equipped with a(n) _____.&#10;A) electric starter&#10;B) primary exciter&#10;C) brushless energizer&#10;D) brushless exciter

Accepted Answer

The answer of An alternator that has a separate small...

Question 14

An alternator containing eight poles per phase is turning at 1500 RPM. What is the output frequency?&#10;A) 70 Hz&#10;B) 80 Hz&#10;C) 90 Hz&#10;D) 100 Hz

Accepted Answer

The answer of An alternator containing eight poles per phase...

Question 15

An alternator containing eight poles per phase is turning at 900 RPM. What is the output frequency?&#10;A) 30 Hz&#10;B) 40 Hz&#10;C) 50 Hz&#10;D) 60 Hz

Accepted Answer

The answer of An alternator containing eight poles per phase...

Question 16

What is one factor that controls the output frequency of an alternator?&#10;A) number of stator poles and rotor rotation speed&#10;B) input voltage&#10;C) number of stator poles and number of rotor bars&#10;D) input voltage and torque

Accepted Answer

The answer of What is one factor that controls the...

Question 17

The revolving armature type alternator is capable of _____ power output and is, therefore, _____ often used than the revolving field type.&#10;A) less; more&#10;B) less; less&#10;C) more; less&#10;D) more; more

Accepted Answer

The answer of The revolving armature type alternator is capable...

Question 18

Using a(n) _____ is one method of preventing induced voltage from becoming excessive.&#10;A) paralleling switch&#10;B) inductive bypass&#10;C) field discharge resistor&#10;D) capacitive resistor

Accepted Answer

The answer of Using a(n) _____ is one method of...

Question 19

What machines operate on the same principle of electromagnetic induction as DC generators, but they have no commutator?&#10;A) alternators&#10;B) transformers&#10;C) oscillators&#10;D) converters

Accepted Answer

The answer of What machines operate on the same principle...

Question 20

Power is carried to the outside circuit of a &#160;revolving armature type alternator &#160;via brushes riding&#160;against the _____.&#10;A) commutators&#10;B) diodes&#10;C) sliprings&#10;D) wires

Accepted Answer

The answer of Power is carried to the outside circuit...

Deck 32: Three Phase Alternators