Guardian Technologies 4390, 4456, 4389, 4760, 4759, 4758 manual Operation

SECTION 2.2

OPERATIONAL ANALYSIS

PART 2

AC GENERATORS

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 excitation or DPE windings, (c) the stator battery charge, and (d) engine run 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 completed to the voltage regulator, via Wire 2, excitation circuit breaker, Wire 162, and Wire 6. Unregulated alternating current can flow from the winding to the regulator.

The voltage regulator "senses" AC power winding output 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 current to the rotor.

The rectified and regulated current flow from the regulator 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.

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 excitation current 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 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 circuit, current can flow in the circuit. The regulated AC power winding output voltage will be in direct proportion to the AC frequency. For example, on units rated 120/240 volts at 60 Hz, the regulator will try to maintain 240 volts (line-to-line) at 60 Hz. This type of regulation 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 current from the battery charger is delivered to the unit battery, via Wire 15, a 15 amp fuse, and Wire 13. This output is used to maintain battery state of charge during operation.

ENGINE RUN WINDING OUTPUT:

A voltage is induced into the engine run winding and delivered to a solid state circuit board , via Wire 66A. This output "tells" the circuit board that the engine has started and what its operating speed is. The circuit board uses these signals from the engine run winding to (a) terminate cranking, and (b) turn on various timing circuits that control automatic operation. See Part 4, "DC Control".

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