Section 3 – Maintenance

Recreational Vehicle Generator

‹2.8.1 DO NOT OVERLOAD THE GENERATOR

Read the rated wattage/amperage capacity of the generator on the generator data decal (see "Generator Identification").

Applying electrical loads in excess of the unit’s rated capacity will cause the engine/generator to automatically shut down.

To avoid overloading, add up the wattage of all connected electrical lighting, appliance, tool and motor loads. This total should not be greater than the generator’s rated wattage capacity.

•Most lighting, appliance, tool and motor loads indicate their required watts on their nameplate or data plate. For light bulbs, simply note the wattage rating of the bulb.

•If a load does not show its rated wattage, multiply that load’s rated VOLTS times AMPS to obtain WATTS.

•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 oper- ated by the generator.

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

2.9PROTECTION SYSTEMS

‹2.9. LOW OIL PRESSURE SWITCH

This switch (Figure 2.4) has normally closed (N.C.) contacts that are held open by engine oil pressure during cranking and operating. Should oil pressure drop below a preset level, switch contacts close, and the engine automatically shuts down. The unit should not be restarted until oil is added.

‹2.9.2 HIGH TEMPERATURE SWITCH

This switch (Figure 2.4), which has normally open (N.O.) contacts, is mounted near the oil filter. The contacts close if the temperature should exceed approximately 293º F (145º C), initiating an engine shutdown.

Figure 2.4 – Low Oil Pressure and
High Temperature Switches

‹2.9.3 FIELD BOOST

The Controller Circuit Board houses a field boost diode and resistor that are not part of the automatic choke circuit. These two components are part of a “field boost” circuit (Figure 2.5). 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 sufficiently strong magnetic field is available to produce “pickup” voltage in the stator windings.

Figure 2.5 – Field Boost Circuit

‹2.9.4 OVERVOLTAGE PROTECTION

A solid-state voltage regulator (Figure 2.6) controls the generator’s AC output voltage. This regulator supplies an excitation current to the rotor. By regulating the rotor’s excitation current, the strength of its magnetic field is regulated and, in turn, the voltage delivered to connected electrical loads is controlled. When the AC frequency is 60 Hertz, voltage is regulated at 120 volts (voltage-to-frequency ratio is 2-to-1).

Figure 2.6 – Solid State Voltage Regulator

The voltage regulator also incorporates a “voltage surge protection circuit.” This circuit prevents troublesome surges in the generator AC output voltage. Voltage surge is a common cause of damage to electronic equipment.

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