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5-3-2 PRIMARY EXCITING ACTION
The RGX Series employs an exciting coil in the engine mag-
neto for raising the primary voltage. This action is explain-
ed. The RG Series generates a voltage when the generator is
started again because of the residual magnetism remaining
in the yokes and poles. If aienerator of this type is disas-
sembled and stored for a long period of time, the residual
FC
magnetism may dissipate so that the generator may not
generate a voltage when it is restarted. The RGX Series
has an exciting coil for primary exciting action to eliminate
such a phenomenon.
The primary exciting action of the new type is explained
below.
ENGINE MAGNETO
Fig. 5- 17(A)
When the generator is started, the permanent magnet on the
engine rotates to genrate 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. 517(A).)
The rotor is turned an electromagnet by that current and
rotates so that voltages are generated in the stator coils
(main coil, sub coil, and DC coil). The voltage generated in
the sub coils is operated by the AVR to feed a current to in-
crease the field coil current (See Fig. 5-17(B).) As a result,
the rotor magnetism increases. This operation is repeated to
generate the rated voltage at 5OHz or 6OHz in the main coil
and DC coil.
5-3-3 VOLTAGE REGULATING MECHANISM
Connect a load to the AC output terminal and increase cur-
rent. Output voltage varies as shown in Fig. 5-17(C) depend-
ing 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 falls 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
increases the current flows to the field coil. As a result, the
rotor magnetism increases, the voltage fallen by the load
current 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.
I
MC
A
SC
c
4
Fig. 5- 17/B)
WITHOUT AVR
RATED VOLTAGE
I
WITH AVR
-A
Fig. 5 17(C)
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