Page 81 - Apprentice Manual_Neat

S3-Q58.) The frequency output of a generator is determined by:

a.) *Prime mover RPM
Correct. The RPM is determined by the number of poles. The fewer number of poles the faster
the rotor must turn.
b.) The external load
Output voltage may suffer with too great a load, but load will have no effect on frequency.
c.) Magnetic strength of the main rotor
Magnetic strength will play a part in the amount of load the generator may carry, but it will play no
role in frequency.
d.) Rectification of the rotating diodes
The rectifier will determine the strength of the magnetic field, but no part in frequency.

S3-Q59.) The exciter rotor produces which type of output?

a.) Direct Current (DC)
The rotor passes (rotates) through a magnetic field and has no commutator or rectifier. It cannot
produce DC.
b.) *Alternating Current (AC)
Correct. Because the rotor rotates through a magnetic field it produces a sine-wave.
No rectification or commutation takes place within the rotor.
c.) Pulsating DC (unfiltered, rectified AC)
No rectification takes place within the rotor.
d.) VARs to correct power factor
Reactive power is only created with capacitors or inductors. While the exciter rotor is an inductor, its
function is not to generate VARs. More inductance would be counterproductive to a usually inductive
load.

S3-Q60.) Generators rated for Standby usage are designed to operate under which of the following
conditions?

a.) Only when needed, not at full load capacity for more than a few seconds (e.g.: to start a motor)
Rated full load is a number that usually can be maintained for at least 50% of the time. Peak load
would be more appropriate for this answer.
b.) At or below 90% of the generators full load rating.
Full load or even 90% of full load should not be maintained indefinitely. Manufacturer’s instructions
may vary.
c.) *Only when needed, limited hours at full load rating
Correct. Manufacturer’s instructions may vary, but a general “rule-of-thumb” is no more than
50% of the run time should be at full load.
d.) Unlimited hours at generator’s full load setting
This would be harmful to most generators. Generators are designed for a maximum load, but should
only maintain that load for a limited time.

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