Why variable, Speed control – Generac Power Systems NP-40G User Manual
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Section 1.1- GENERATOR FUNDAMENTALS
Why Variable
Most electrical loads will operate satisfactorily
only within a relatively small voltage band. In order
to provide useful voltage at larger load currents, It
is necessary to increase engine speed.
In conventional AC generators, some form of
voltage regulation Is needed to provide correct
voltage in the full range of load current. This Is
often accomplished by regulating excitation cur
rent to the Rotor (fíelo) which then regulates the
strength of the Rotor’s magnetic field. The voltage
Induced Into the Stator windings Is proportional to
the strength of the Rotor’s magnetic field.
Speed Control?
The CCG uses a Rotor having a fixed and perma
nent magnetic field. The strength of this magnetic
field Is fixed and cannot be regulated.
The output voltage on CCG generators tends to
droop with Increasing electrical loads. The SYS
TEM CONTROLLER maintains a constant AC out
put voltage by Increasing engine and Rotor speed
as the load current increases, to offset this Inherent
voltage droop.
The SYSTEM CONTROLLER also selects the cor
rect number of generator pulses which are com
bined to form each 60 Hertz "half-cycle“.