Hobart 60CU20 Operation And Maintenance Manual With Illustrated Parts List page 34

OM-2226 / Operation and Maintenance Manual
60CU20 / Series 500062 / 400 Hz. Generator Set
(5) Voltage regulator PC board [REG] (A4)
This voltage regulator PC board is designed to provide voltage regulation for a three-phase, four-
wire, 115/200-volt, 400-Hz brushless alternator. This regulator provides field excitation power as
required to meet varying alternator load conditions to hold the alternator voltage constant. In
addition, the voltage regulator PC board circuitry provides line-drop compensation. Any deviation
of the alternator voltage from its set, regulated level is sensed at the voltage regulator PC board.
The sensing signal is compared to a reference signal, and, with associated circuitry, varies the
field power supplied to the rotary exciter.
•
When the machine is started, and the engine is at rated speed, the rotary exciter is excited
from alternator residual magnetism through the half-wave rectifier-bridge, located on the
voltage regulator PC board assembly. As the rotary exciter voltage increases, alternator
excitation increases and the alternator voltage builds up. The sensing circuit of the voltage
regulator PC board then compares the input voltage to a reference voltage and adjusts the
field power of the rotary exciter to bring the voltage into regulation limits.
•
When the alternator is loaded, its terminal voltage decreases, lowering the rectified three-
phase voltage of the voltage sensing circuit. The sensing voltage is low in respect to its
reference voltage, causing the voltage regulator PC circuitry to increase the power to the field
of the rotary exciter. The alternator voltage increases until the voltage returns to its regulated
value.
May 2, 2013
Figure 9: Digital Control PC Board
Chapter 1-1
Page 18