EGCP-2 Engine Generator Control Package Manual 26174
146 Woodward
Chapter 6.
Calibration of Control Inputs and Outputs
Introduction
The EGCP-2 can be thought of as a digital metering device that monitors engine,
generator, bus, and mains analog signals. Being a digital metering device, the
EGCP-2 must be properly calibrated in order to perform its role as a controlling
device accurately. This chapter discusses the calibration of these various inputs
and outputs of the EGCP-2, and the effects of the calibration on the metering and
control functions of the EGCP-2.
The EGCP-2 inputs and outputs are factory calibrated for the best possible
tolerance between the input signal, and the signal as sensed by the EGCP-2. All
analog signals coming into the EGCP-2 are routed through analog to digital (A/D)
converters. These converters have the ability to be “calibrated” so that the input
signals sensed by the EGCP-2 software are equal to the true input signal.
While the factory calibration brings the EGCP-2 control within close tolerance of
the various inputs as fed into the control, it cannot account for losses in field
wiring that are common in power generation applications. Signal loss due to wire
length and impedance, transformer primary to secondary losses, and non-
linearity of sending devices cannot be calibrated out at the factory. This is why
the EGCP-2 must be calibrated upon commissioning.
The intent of calibrating the EGCP-2 is to make the unit read out the various
voltages, currents, frequencies, and temperatures in the various status menu
display screens as close as possible to what is actually occurring at the true
source of these signals.
For example, assume there is a 480 volt line-to-line generator set operating in a
system that uses 4:1 voltage transformers to feed the EGCP-2. The input AC line
to line voltage at the EGCP-2 is 118 volts due to primary to secondary losses
across the voltage transformers. The EGCP-2 Generator Status menu will
display a generator voltage of 472 Vac L-L for each phase, which is not truly
what the generator is producing. In this case, the Calibration tuning menu would
be used to adjust the A/D converters on the three generator voltage transformer
inputs until the Generator Status menu reads 480 Vac L-L for each phase. This is
how the calibration menu is used to compensate for losses in signal between the
source, and the EGCP-2. The calibration menu allows adjustment of all the
analog inputs and outputs of the EGCP-2.
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