Multiquip SG1400C3 general information, Generator, Engine, Principle Of Operation, Battery

general information

Generator

The MQ Power Model SG1400C3 is a 200kVA studio generator that is designed as a high quality power source for entertainment and studio applications.

In keeping with Multiquip's policy of constantly improving its products, the specifications quoted herein are subject to change without prior notice.

Permanent Magnet Generator Excitation System

The SG1400C3 generator is equipped with a PMG (Permanent Magnet Generator) generator end. The excitation system provides a minimum short circuit support current of 300% of the standby rating for 10 seconds at 60 Hz, and approximately 275% at 50 Hz.

Both the PMG and the exciter are mounted outboard of the bearing for ease of maintenance. The rotating brushless exciter features hermetically sealed diodes for three-phase full-wave rectification. The three-phase bridge is protected against abnormal transient conditions by a multiplate selenium surge protector.

Engine

This generator is powered by a six-cylinder, 4-cycle direct injection, turbocharged, air-cooled Cummins QSB7-G5 diesel engine. Engine speed is set at the factory at 1800 RPM. This engine is designed to meet every performance requirement for the generator. Refer to Table 2 for engine specifications.

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.

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%.

Battery

The battery system is located in the engine compartment on the sub-base. The battery’s primary purpose is to provide starting power for the diesel engine starter motor. The battery system is comprised of two 12 VDC, sealed lead acid batteries wired in series to provide 24 VDC to the starting motor. The battery is charged by the charging alternator while the engine is engaged.

Exhaust System

The exhaust system is located above the diesel engine.The exhaust system is comprised of rigid and flexible tubing, a silencer, and a roof-mounted exhaust riser with a rain cap.

page 16 — SG1400C3 Studio Generator • operation manual — rev. #0 (10/05/11)