Generac Power Systems IM Series - Manual (Page 7)

when determining a-c frequency, Rotor rpm and number
of Rotor poles.
rpm X No. of Rotor Poles
Frequency = 2 x 60
2 X 60 X Frequency
RPM = No. of Rotor Poles
2 X 60 X Frequency
Rotor Poles= rpm
Relationship of Voltage and Frequency
Engine governed speed and a-c voltage are adjusted with
no electrical loads applied to the generator (no-load).
That is, the a-c voltage is set at a fixed ratio to a-c
frequency. Recommended frequency and voltage set­
tings are as follows:
Set Frequency to:
Set Voltage to;
60.5 to 63.5 Hz
121 to 127 volts*
*Llne-to-Neutral Voltage
Generator a-c Connection System
D
Series NP45G, NP55G and NP65G RV generators
are equipped with dual Stator a-c power windings. These
windings may be connected in parallel to provide a 120-
votts a-c output as shown. Note that customer loads of
up to 30 a-c amperes may be connected across Wires T1
(red) and T2 (white); loads up to 20 a-c amperes across
wires T2 (white) and T3 (black).
E
The generator’s a-c output leads may be reconnected
in series, to supply a dual voltage (120 and/or 240 volts)
a-c output. When this is done, connect 240 volts a-c
loads across T1 (red) and T3 (black); 120 volts across T1
(red) and T2 (white) or T3 (black) and T2 (white). T2 is
the neutral wire.
Effects of Engine Power
The generator engine must develop sufficient power to
operate the generator under varying electrical loads. The
greater the wattage (amperage) demands ot connected
electrical loads, the greater the engine power needs. As
a general rule, approximately 2 engine horsepower is
ne^led for each 1000 watts (1.0 kW) of generator power
output.
If the generator’s wattage/amperage capacity is ex­
ceeded, engine power may not be adequate to handle
the increased load. The result will be a decrease in
engine rpm, a corresponding decrease In generator a-c
output voltage and frequency, and internal generator
overheating.
A badly worn engine, one that has lost compression, or
one with defective fuel. Ignition or air Intake system may
not be able to handle loads within the generator's rated
capacity. Problems with generator a-c output are often-
caused by an engine problem.
NOTE: A shorted condition In one or more con
nected electrical loads or In generator windings can
dramatically Increase the power demands on the
driving
engine. Such shorted conditions may
present the same symptoms as an underpowered
engine.________________________________________
Effects of Dirt and Moisture oh RV
Generators
If moisture is permitted to remain in contact with gener­
ator windings, some of that moisture may be retained in
cracks and voids of the winding insulation. This will
cause a reduced insulation resistance. However,
prolonged exposure to moisture resistance of stator and
rotor winding Insulation. Dirt can make the problem
worse, since it tends to hold moisture into contact with
windings. Salt (as from sea air) also makes the problem
worse, since salt will absorb moisture from the air. When
salt and moisture combine, they form a good electrical
conductor.
Because of the detrimental effects of dirt and moisture,
the generator should be kept as clean and as dry as
possible. Stator and rotor windings should be tested
periodically, using an insulation resistance tester (Hi-Pot
or megohmmeterX If insulation resistance is excessively
low, drying may be required to remove moisture. After
drying, a second test of insulation resistance is still low
after drying, replacement of defective windings may be
necessary.