Operation - Guardian 5240 Diagnostic Repair Manual

SECTION 2.2
OPERATIONAL ANALYSIS

OPERATION

STARTUP:
When the engine is started, residual plus field boost
magnetism from the rotor induces a voltage into (a)
the stator AC power windings, (b) the stator exci-
tation or DPE windings, and (c) the stator battery
charge winding. In an "on-speed" condition, residual
plus field boost magnetism are capable of creating
approximately one-half the unit's rated voltage.
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 com-
pleted to the voltage regulator, via Wire 2 and Wire
6. Unregulated alternating current can flow from the
winding to the regulator.
The voltage regulator "senses" AC power winding out-
put voltage and frequency via stator Wires 11 and 22.
The regulator changes the AC from the excitation
winding to DC. In addition, based on the Wires 11 and
22 sensing signals, it regulates the flow of direct cur-
rent to the rotor.
The rectified and regulated current flow from the regu-
lator is delivered to the rotor windings, via Wire 4, and
the positive brush and slip ring. This excitation current
flows through the rotor windings and is directed to
ground through the negative (-) slip ring and brush,
and Wire 0.
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PART 2
The greater the current flow through the rotor wind-
ings, 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 excitation current to the rotor until volt-
age 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 excitation current. 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 cir-
cuit, current can flow in the circuit. The regulated AC
power winding output voltage will be in direct propor-
tion to the AC frequency. For example, on units rated
120/240 volts at 60 Hz, the regulator will try to main-
tain 240 volts (line-to-line) at 60 Hz. This type of regu-
lation system provides greatly improved motor starting
capability over other types of systems.
BATTERY CHARGE WINDING OUTPUT:
A voltage is induced into the battery charge windings.
Output from these windings is delivered to a battery
charger, via Wires 66 and 77. The resulting direct cur-
rent from the battery charger is delivered to the unit
battery, via Wire 13. This output is used to maintain
battery state of charge during operation.
AC GENERATORS