Generac Power Systems CorePower 6/7 kW 60 Hz Diagnostic Repair Manual page 30

Section 2.2
Operational Analysis
STARTUP
When the engine is started, permanent magnets embedded in
the rotor induce a voltage into (a) the stator AC power windings,
(b) the stator excitation or DPE windings. In an "on-speed"
(engine cranking) condition, this magnetism is capable of creating
approximately one to three volts AC.
ON-SPEED OPERATION
As the engine accelerates, the voltage that is induced into the
stator windings increases rapidly, due to the increasing speed at
which the rotor operates.
FIELD EXCITATION
An AC voltage is induced into the stator excitation (DPE) windings.
The DPE winding circuit is delivered to the voltage regulator
through the two Blue Wires and C1-1 and C1-2. Unregulated
alternating current flows from the winding to the regulator. The
voltage regulator "senses" AC power winding output voltage and
frequency through the Green and White Wires.
The regulator changes the AC from the excitation winding to DC
Field Excitation. In addition, based on the AC sensing wires, it
regulates the flow of direct current to the rotor. The rectified and
regulated current flow from the regulator is delivered to the rotor
windings through the positive (+) wire and the positive brush and
ENGINE -
DIRECT
DRIVE
Page 28
TO LOAD
MLB
MLB = MAIN LINE CIRCUIT BREAKER
STATOR STATOR
POWER POWER
WINDING WINDING
MAGNETIC
FIELD
ROTOR
MAGNETIC
FIELD
Figure 20. Operating Diagram
PART 2
slip ring. This excitation voltage flows through the rotor windings
and through the negative (-) slip ring and brush on the negative
(-) wire.
The greater the current flow through the rotor windings, the more
concentrated the lines of flux around the rotor become. The more
concentrated the lines of flux around the rotor that cut across the
stationary stator windings, the greater the voltage that is induced
into the stator windings.
Initially, the AC power winding voltage sensed by the regulator is
low. The regulator reacts by increasing the flow of field excitation
voltage to the rotor until voltage increases to a desired level. The
regulator then maintains the desired voltage. For example, if
voltage exceeds the desired level, the regulator will decrease the
flow of field excitation voltage. Conversely, if voltage drops below
the desired level, the regulator responds by increasing the flow of
excitation current.
AC POWER WINDING OUTPUT
A regulated voltage is induced into the stator AC power windings.
When electrical loads are connected across the AC power
windings to complete the circuit, current can flow in the circuit.
SENSING
STATOR
EXCITATION
WINDING
AC GENERATORS
VOLTAGE
REGULATOR