Generac Power Systems 6872-3 Owner's Manual page 6

NOTE
The generator has a momentary SURGE CAPACITY
of up to 80,000 watts (80.0 kW). This feature
is beneficial when starting electric motors,
since many motors require more power for
starting than for continuous operation.
1.4-
OPERATING
SPEEDS
Correct rated a-c voltage and frequency can
be supplied by this equipment only when its
revolving field is operating at the correct
rated speed (approximately 3600 rpm).
To
operate the revolving field at its proper
rated speed, the power takeoff (PTO) shaft
which drives the unit must provide an input
drive speed of approximately 540 rpm. A heavy
duty GEARBOX provides the necessary "step-up"
in operating speed, from 540 to 3600 rpm.
Generator operating speed, a-c frequency and
voltage are directly proportional to each
other. A VOLTMETER is provided on the unit,
to provide an indication that voltage and
operating speed are correct. Operate the
generator ONLY AT ITS CORRECT RATED VOLTAGE
and at a 540 rpm PTO shaft inpuit speed.
DANGER!
High operating speeds are extremely dangerous
and may result in personal injury or severe
damage to equipment. High operating speeds
will also result in an OVERVOLTAGE/OVERFREQ-
UENCY condition. Operation at low speeds will
result in an UNDERVOLTAGE and UNDER FREQUENCY
condition. Some connected electrical loads
may be damaged by incorrect voltage and/or
frequency. In addition, sufficient horsepower
for generator operation may not be supplied
at lower PTO shaft speeds.
1.5-
COOLING
AIR FLOW
This equipment requires an adequate flow of
cooling air for continued proper operation.
Without sufficient air flow into and out of
the unit, it will quickly overheat and cause
damage to the generator and/or surrounding
property. Operate this unit only in free air.
NEVER operate the unit inside any compartment
or enclosure that might tend to obstruct the
free flow of cooling air into or out of the
unit.
1.6- OVERMHIMATURE PROTECTION
A THERMAL PROTECTOR is imbedded in windings
of the generator stator. This device is a
normally-closed (N.C.) temperature sensitive
switch that will open when internal generator
temperatures exceed a pre-set, safe value. On
switch opening, little or no a-c output will
be supplied by the unit. The device is self
resetting so that, when internal temperatures
decrease to a safe level, the switch contacts
will again close and normal a-c output will
resume. Should the unit's a-c output be lost,
immediately disconnect all electrical loads,
wait about 5 minutes and reconnect loads.
Make sure the rated maximum continuous a-c
power capacity of the generator
is not
exceeded.
Opening of the Thermal Protector contacts and
loss of a-c output may be caused by any of
the following:-
a. Inadequate cooling air flow
b. A shorted condition in the generator
c. A shorted condition in one of the
connected electrical loads
d. Exceeding the generator's rated
wattage/amperage capacity.
1.7-
THYRISTOR
OR
SILICONE CONTROLLED
RECTIFIER
LOADING
Solid state electronic control devices which
utilize THYRISTOR or SCR firing circuits
(such as variable frequency induction motor
controls, precision motor controls, no-break
powered battery chargers, etc.) can introduce
high frequency harmonics which adversely
affect or distort the normal generator
waveform. This creates additional heat in the
generator and may result in overheating and
opening of the thermal protector. Such
devices often present problems to non-utility
power generating equipment or to any limited
power buss system. The problems that can
occur are not limited to
the generator
itself, but can affect the solid state
control devices or the devices they control.
In addition, other associated
loads,
monitoring devices, or a number of
combinations over the entire system can be
adversely affected. GENERAC generators can
supply
Some THYRISTOR or SCR loads when
properly applied. For a single thyristor load
the maximum kva load on the generator should
be limited to about 6016of the unit rated ca-
pacity. Where thyristor or SCR loading is
less than 3096 of the total loading, generator
de-rating is generally not required. It is
recommended that the control manufacturer,
systems engineer, and GENERAC work closely
together to ensure the proper selection of
all components in such a system.
1.8- GENERATOR A-C
WIRING CONNECTIONS
TFigure
This single phase generator employs a stator
assembly having a dual set of a-c power
windings and a 3-wire connection system. In
this type of system, Wires 820 and #30 are
the HOT leads; Wire 810 is the NEUTRAL lead.
Figure 1-2. Single Phase, 3-Wire
Connection System
4