Section 1: Generator Fundamentals - Generac Power Systems 4451 & 4986 Repair Manual

BCR2
12V DC
OUTLET
CB1
2. During startup, printed circuit board action controls the START/
STOP RELAY to deliver 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), battery charge and AC Power wind-
ings.
4. Excitation winding unregulated AC output is delivered 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 cur-
rent 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.
STATOR
POWER
WINDING
ENGINE -
DIRECT DRIVE
STATOR
BATTERY CHARGE
WINDING
BCR1
10A STATOR
BATTERY CHARGE
Figure 1-7. – Generator Operating Diagram
geneRatoR FunDaMentals
STATOR
POWER
WINDING
ROTOR
STATOR
DPE
WINDING
BCR1 & BCR2 = BATTERY CHARGE RECTIFIER
WINDING
CB2 = EXCITATION CIRCUIT BREAKER
(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.
a. Battery charge winding AC output is deliv-
ered to the battery charge rectifiers (BCR)
which changes the AC to direct current
(DC).
b. The rectified DC is then delivered to the
units battery and battery charge outlet, to
maintain the battery in a charged state.
FIELD BOOST FROM
START/STOP RELAY (SSR)
VOLTAGE
REGULATOR
CB2
section 1
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