Generator Performance
Generator Loading
When a generator is installed or reconnected, be sure
the total current in one phase does not exceed the
nameplate rating. Each phase should carry the same
load, allowing the engine to work at its rated capacity.
An electrical unbalance can result in an electrical
overload and overheating if one phase exceeds the
nameplate amperage. Any unbalanced load that’s
required should be placed on phase 2, since current
sensing for voltage regulator is on that phase.
Power Factor
Power factor may be thought of as the efficiency of the
load the ratio of apparent power to total power. Power
factor is expressed as a decimal and denotes that
portion of current supplied to a system doing useful
work. The portion of current not doing useful work is
absorbed in maintaining the magnetic field in motors.
This current, although it is called the reactive load, does
not require engine horsepower to maintain it.
In most applications electric motors and transformers
determine the power factor of the system. Induction
motors usually have a .8 power factor. Incandescent
lighting is a resistive load for about 1.0 power factor, or
unity.
The power factor of a system may be determined by a
power factor meter or by calculations. Determine the
power requirement in KW by multiplying the power factor
by the KVA supplied to the system. As the power factor
goes up the total current supplied to a constant power
demand will go down. A 100 KW load at a .8 power
factor will draw more current than a 100 KW load at .9
power factor. A higher power factor increases the
possibility of overloading the engine.
A lower power factor increases the possibility of
overloading the generator.
Low Idle Adjustment
Electric sets require higher low idle setting than do
industrial engines. Low idle must not be below 2/3 the
full load speed of 60 Hz units (4/5 full load speed of 50
Hz units).
CAUTION
Disconnect the exciter circuit by removing fuses F1
and F2 (on SRCR) or Fuse F1 (on SR 4) before
operating the engine below the low Idle rating.
Failure to do this will result in generator damage.
On electric sets with Woodward governors, there is no
low idle stop. On electric sets with mechanical
governors and natural gas electric sets, the low idle is
set at the factory, and should only be adjusted by your
Caterpillar dealer if adjustment is required.
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