Multiquip MQP20P manual Principle of operation, Engine, ElectrONIC Governor System

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%.

MQP20P STANDBY GENERATOR • operation and parts manual — rev. #1 (11/28/11) — page 17