Generac Power Systems 9592-3 - Manual (Page 11)

ADDITIONAL INFORMATION
This section discusses some of the engine protective
devices, overload protection and breaking in a new
generator.
AUTOMATIC LOW OIL PRESSURE
SHUTDOWN
The engine is equipped with a normally-closed (N.C.)
oil pressure switch (Figure 4). Engine oil pressure holds
the switch open during cranking and operation. Should
oil pressure drop below about 2-6 PSI, the switch con­
tacts close and the engine automatcially shuts down.
Figure 4
—
Switches for Enghe Safety Shutdown
HIGH TEMPERATURE SHUTDOWN
An oil temperature switch (Figure 4) with normally-open
(N.O.) contacts is mounted near the oil filter. If oil
temperature were to exceed about 284®F (140“C), the
switch contacts close and the engine shuts down.
FIELD BOOST
The Controller Circuit Board houses a field boost diode
and resistor which are not part of the automatic choke
circuit. These two components are part of a "field boost"
circuit (Figure 5). During engine cranking only, a posi­
tive DC (battery) voltage is delivered through the diode,
resistor, brushes and slip rings, and to the generator
rotor. Application of this voltage to the rotor "flashes the
field’ whenever it is started. Hashing of the field each
time the generator starts makes sure that a sufficiently
strong magnetic field is available to produce the re­
quired "pick up" voltage in the stator windings.
OVER VOLTAGE PROTECTION
A solid state voltage regulator (Rgure 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 electricaJ loads is controlled. When the AC
frequency is 60 Hz, voltage is regulated at 120 volts
(voltage-to-frequency ratio is 2-to-1).
The voltage regulator also incorporates a "voltage surge
protection circuit." This circuit prevents troublesome
surges in the generator AC ou^ut voltage. Voltage
surge is a common cause of damage to electronic
equipment.
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