Voltage Regulator; Adjustment Procedure - Generac Power Systems 4451 & 4986 Repair Manual

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Figure 3-5. – Excitation Circuit Breaker

VOLTAGE REGULATOR:

A typical Voltage Regulator is shown in Figure 3-6
(12.5 & 15 kW Units) or Figure 3-7 (17.5 kW Units).
Unregulated AC output from the stator excitation
winding is delivered to the regulator's DPE termi-
nals, via Wire 2, the Excitation Circuit Breaker and
Wire 162, and Wire 6. The Voltage Regulator recti-
fies that current and, based on stator AC power
winding sensing, regulates it. The rectified and
regulated excitation current is then delivered to the
rotor windings from the positive (+) and negative (-)
regulator terminals, via Wire 4 and Wire 0. Stator
AC power winding "sensing" is delivered to the reg-
ulator "SEN" terminals via Wires 11S and 44S.
The regulator provides "over-voltage" protection, but
does not protect against "under-voltage". On occur-
rence of an "over-voltage" condition, the regulator will
"shut down" and complete loss of excitation current
to the rotor will occur. Without excitation current, the
generator AC output voltage will drop to approximately
one-half (or lower) of the unit's rated voltage.
Figure 3-6. – Typical Voltage Regulator Found on 12.5
kW and 15 kW Units
162
DescRiption & coMponents
Figure 3-7. – Typical Voltage Regulator Found on 17.5
ADJUSTMENT PROCEDURE (12.5 AND 15 KW UNITS):
The Voltage Regulator is equipped with three light
emitting diodes (LED's). These LED's are normally
on during operation with no faults in the system The
RED regulator LED is on when the regulator is on
and functioning. The Yellow sensing LED is powered
by sensing input to the regulator from the stator AC
power windings. The GREEN excitation LED is pow-
ered by stator excitation winding output.
Four adjustment potentiometers are provided. They
are VOLTAGE ADJUST, GAIN, STABILITY, and
UNDERFREQUENCY ADJUST.
1. Connect an AC Voltage/Frequency meter across wires 11 & 44
at the 50A Main circuit breaker. Verify frequency is between
59-61Hz.
2. On the regulator, set the adjustment pots as follows.
a. Voltage Adjust – Pot-turn fully counterclockwise
b. Gain – turn to midpoint (12 O'clock)
c. Stability – turn to midpoint (12 O'clock)
d. Under Frequency – turn to midpoint (12 O'clock)
3. Start the generator. This adjustment will be done under a no-
load condition.
4. Turn the regulator's Voltage Adjust pot clockwise to obtain a line
to line voltage of 238-242 VAC.
5. If the red regulator LED is flashing, slowly turn the stability pot
either direction until flashing stops.
ADJUSTMENT PROCEDURE (17.5 KW UNITS):
A single red lamp (LED) glows during normal opera-
tion. The lamp will become dim if excitation winding
AC output diminishes. It will go out on occurrence of
an open condition in the sensing AC output circuit.
An adjustment potentiometer permits the stator AC
power winding voltage to be adjusted. Perform this
adjustment with the generator running at no-load, and
section 3
Units
Page 11