Hobart 60CU24, Operation And Maintenance Manual With Illustrated Parts List, Page: 34 / 234

OM-2098C / Operation and Maintenance Manual
60CU24 / Series 500060C / 400 Hz. Generator Set
November 16, 2007
Revision 8 Chapter 1-1
Page 20
b 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.
c When a load is removed from the alternator, the alternator voltage rises. The rectified three-
phase voltage-sensing signal increases, causing this signal to be higher than the reference
signal. The associated voltage regulator circuitry causes the field power of the rotary exciter
to decrease, lowering the alternator voltage until the voltage returns to regulated value. The
line drop voltage compensation circuit consists of a current transformer on each phase of the
load circuit, and fixed resistance in parallel with each current transformer. The current
transformers detects the magnitude of current flowing through the power cables from the
alternator to its load and feeds a signal into the voltage regulator PC board. The PC board
processes this signal to change the output voltage proportional to the current draw. The
regulator output increases slightly so that the alternator output voltage is equal to the
regulated voltage plus the voltage drop in the lines. The line drop compensation
potentiometer may be adjusted to match exactly the voltage drop of the power cables
carrying the load current.
The under/over frequency protection, EF signal, and lost neutral detection are also monitored by
the REG and will signal the CTL when a fault has occurred. The CTL issues the appropriate
command that corresponds to the fault.
(8) Transformer-Rectifier PC Board [TRB] (A404) {Optional with TR, Reference Appendix A}
The TRB PC Board (see Figure 15) is only used when the optional 28.5 VDC transformer-rectifier
assembly is installed. The TR monitors the output voltage, output current, controls the input and
output contactors, and monitors all fault events associated with the DC output. When a fault event
does occur the TRB relays this information to the CTL. The CTL will issue the command to the
system that fits the fault event.
(9) +5, -12 VDC Power Source (PS1)
Supplies the internal power distribution of +5 VDC and –12 VDC into the control system.
Control System Power Source
Figure 14