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MQP20P STANDBY GENERATOR • OPERATION AND PARTS MANUAL — REV. #1 (11/28/11) — PAGE 17
GENERAL INFORMATION
PRINCIPLE OF OPERATION
This generator is a brushless, self-excited, externally
voltage regulated, synchronous AC generator. The
generator is made up of six major components: main stator
(armature), main rotor (field), exciter stator (field), exciter
rotor (armature), rectifier assembly, and voltage regulator.
The generator's exciter consists of a stationary field and
a rotating armature. The stationary field (exciter stator)
is designed to be the primary source of the generator's
residual magnetism. This residual magnetism allows the
exciter rotor (armature) to produce AC voltage even when
the exciter stator (field) is not powered. This AC voltage
is rectified to DC by the rotating rectifier assembly and
fed directly to the main rotor (field). As the generator
shaft continues to rotate, the main rotor (field) induces a
voltage into the generator's main stator (armature). At rated
speed, the main stator's voltage produced by the residual
magnetism of the exciter allows the automatic voltage
regulator to function.
The regulator provides voltage to the exciter resulting in
a build-up of generator terminal voltage. This system of
using residual magnetism eliminates the need for a special
field flashing circuit in the regulator. After the generator
has established the initial residual voltage, the regulator
provides a controlled DC field voltage to the exciter stator
resulting in a controlled generator terminal voltage.
VOLTAGE REGULATION
In the standard configuration (shunt excited), the automatic
voltage regulator receives both its input power and voltage
sensing from the generator's output terminals. The regulator
automatically monitors the generator's output voltage
against an internal reference set point and provides the
necessary DC output voltage to the exciter field required
to maintain constant generator terminal voltage. The
generator's terminal voltage is changed by adjusting the
regulator's reference set point.
ENGINE
This standby generator incorporates a Perkins 404D-22
Tier 4 diesel engine. This engine is designed to meet every
performance requirement for the generator. Refer to Table 2
for engine specifications.
In keeping with Multiquip’s policy of constantly improving
its products, the specifications quoted herein are subject
to change without prior notice.
ELECTRONIC GOVERNOR SYSTEM
The electronic governor system controls the RPMs of the
engine. When the engine demand increases or decreases,
the governor system regulates the frequency variation to
± 0.25%.