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4-3 DESCRIPTION of GENERATOR OPERATION
4-3-l PRIMARY EXCITING ACTION
(RGV12000)
When the generator is started, the perma-
nent magnet on the engine rotates to genera-
tor a voltage in the exciting coil.
This voltage is regulated by a diode in the
AVR to feed a current to the generator field
coil. (FC). (See Fig. 4-1)
The rotor is turned an electromagnet by that
current and rotates so that voltage are gener-
ated in the stator coils (main coil and sub
coil). The voltage generated in the sub coils
is operated by the AVR to feed a current to
increase the field coil current. (See Fig. 4-2)
As a result, the rotor magnetism increases.
This operation is repeated to generate the
rated voltage at 50 Hz or 60 Hz in the main
coil and DC coil.
4-3-2 VOLTAGE REGULATING MECHANISM
(RGV12000)
Connect a load to the AC output terminal and
increase current. Output voltage varies as
shown in Fig. 4-3 depending on whether an
automatic voltage regulator is used or not.
The operation of the AVR is explained below.
When an AC output is taken, the engine is
loaded and its rpm falls, Also the AC voltage
fails due to the voltage drop caused by the
internal resistance of the coils. The AVR
detects this voltage drop and its built-in SCR
automatically increase the current flows to
the field coil. As a result, the rotor magnetism
increase, the voltage fallen by the load cur-
rent is raised, and the output voltage is kept
constant. If the AC output is reduced, the
SCR operates in the opposite way to similarly
keep the output voltage constant.
FC
EC ;
ENGINE MAGNETO
Fig. 4-1
AVR
Fig. 4-2
WITHOUT AVR
RATED VOLTAGE
WITH AVR
Fig. 4-3
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