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Section 1
GENERATOR FUNDAMENTALS
NOTE: AC output frequency at 3720 rpm will be
about 60 Hertz. The “No-Load” is set slightly high
to prevent excessive rpm, frequency and voltage
droop under heavy electrical loading.
Generator operation may be described briefly as fol-
lows:
1. Some “residual” magnetism is normally present in
the Rotor and is sufficient to induce approximately
7 to 12 volts AC Into the STATOR’s AC power
windings.
2. During startup, a Printed Circuit Board (PCB)
delivers battery voltage to the ROTOR, via the
brushes and slip rings.
a. The battery voltage is called “Field Boost”.
b. Flow of direct current through the ROTOR
increases the strength of the magnetic field
above that of “residual” magnetism alone.
3. “Residual” plus “Field Boost” magnetism induces
a voltage into the Stator excitation (DPE) and AC
Power windings.
4. Excitation winding unregulated AC output is deliv-
ered to an electronic voltage regulator, via an
excitation circuit breaker.
a. A “Reference” voltage has been preset into
the Voltage Regulator.
b. An “Actual” (“sensing”) voltage is delivered to
the Voltage Regulator via sensing leads from
the Stator AC power windings.
c. The Regulator “compares” the actual (sens-
ing) voltage to its pre-set reference voltage.
(1) If the actual (sensing) voltage is great-
er than the pre-set reference voltage, the
Regulator will decrease the regulated current
flow to the Rotor.
(2) If the actual (sensing) voltage is less than
the pre-set reference voltage, the Regulator
will increase the regulated current flow to the
Rotor.
(3) In the manner described, the Regulator
maintains an actual (sensing) voltage that is
equal to the pre-set reference voltage.
NOTE: The Voltage Regulator also changes the
Stator excitation windings alternating current (AC)
output to direct current (DC).
5. When an electrical load is connected across the
Stator power windings, the circuit is completed
and an electrical current will flow.
6. The Rotor’s magnetic field also induces a voltage
into the Stator battery charge windings.
Page 5
Figure 1-7. – Generator Operating Diagram