Guardian 4389 Repair Manual page 30

SECTION 2.1
DESCRIPTION & COMPONENTS
Figure 5. Excitation Circuit Breaker
VOLTAGE REGULATOR:
A typical voltage regulator is shown in Figure 6.
Unregulated AC output from the stator excitation
winding is delivered to the regulator's DPE terminals,
via Wire 2, the excitation circuit breaker, Wire 162,
and Wire 6. The voltage regulator rectifies that current
and, based on stator AC power winding sensing, reg-
ulates it. The rectified and regulated excitation current
is then delivered to the rotor windings from the posi-
tive (+) and negative (-) regulator terminals, via Wire
4 and Wire 1. Stator AC power winding "sensing" is
delivered to the regulator "SEN" terminals via Wires
11 and 22.
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 approximate-
ly one-half (or lower) of the unit's rated voltage.
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PART 2
Figure 6. Typical Voltage Regulator
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
with a 62 Hz AC frequency (62 Hz equals 3720 rpm).
At the stated no-load frequency, adjust to obtain a
line-to-line AC voltage of about 252 volts.
MAIN LINE CIRCUIT BREAKER:
The main line circuit breaker protects the generator
against electrical overload. See "Specifications" in
front of manual for amp ratings.
AC GENERATORS