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PAGE 16 — SG1400C3 STUDIO GENERATOR • OPERATION AND PARTS MANUAL — REV. #1 (02/15/12)
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.