Generac 00919-0 Field Boost, Automatic LOW OIL Pressure Shutdown, Overvoltage Protection

® GENERACCORPORATION

Generac NP-50LPG Recreational Vehicle Generator

Induction type motors (such as those that run the vehicle’s furnace fan, refrigerator, air conditioner, etc.) need about 2- 1/2 time more watts of power for starting than for running (for a few seconds during motor starting). Be sure to allow for this when connecting electrical loads to the generator. First, figure the watts needed to start electric motors in the system. To that figure, add the running wattages of other items that will be operated by the generator.

Do not apply heavy electrical loads for the first two or three hours of operation.

ADDITIONAL INFORMATION

FIELD BOOST

The Controller Circuit Board houses a field boost diode and resistor which are part of a “field boost” circuit (Figure 5). During engine cranking only, a positive DC (battery) voltage is delivered through the diode, resistor, brushes and slip rings, and the generator rotor. Application of this voltage to the rotor “flashes the field” whenever it is started. Flashing of the field each time the generator starts makes sure that a suffi- ciently strong magnetic field is available to produce “pick-up” voltage in the stator windings.

This section discusses some the the engine protective devices,	Figure 5 — Field Boost Circuit
overload protection and breaking in a new generator.

AUTOMATIC LOW OIL PRESSURE

SHUTDOWN

The engine is equipped with a normally-closed (N.C.) oil pres- sure switch (Figure 4). Engine oil pressure holds the switch open during cranking and operation. Should oil pressure drop below a pre-set level, the switch contacts close and the engine automatically shuts down.

HIGH TEMPERATURE SHUTDOWN
A temperature switch (Figure 4) with normally-open (N.O.) con-	OVERVOLTAGE PROTECTION
tacts is mounted near the oil filter. If engine temperature were
to exceed about 284°F (140°C), the switch contacts close	A solid state voltage regulator (Figure 6) controls the gener-
and the engine shuts down.	ator’s AC output voltage. This regulator supplies an excitation
Figure 4 — Switches for Engine	current to the rotor. By regulating the rotor’s excitation cur-
	rent, the strength of its magnetic field is regulated and, in
Safety Shutdown	turn, the voltage delivered to connected electrical loads is
HIGH TEMPERATURE	controlled. When the AC frequency is 60 Hz, voltage is reg-
SWITCH	ulated at 120 volts (voltage-to-frequency ratio is 2-to-1).
	Figure 6 — Solid State Voltage Regulator
LOW OIL PRESSURE SWITCH
R e c r e a t i o n a l V e h i c l e G e n e r a t o r
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