Rockwell Automation 1407-CGCM Combination Generator Control Module - Manual (Page 64)

64 Rockwell Automation Publication 1407-UM001G-EN-P - April 2013
Chapter 3 CGCM Unit Operation
Limit defines the maximum per unit load share error reported to the host
controller.
Rate defines the maximum change in the load share error per CGCM unit
update cycle, expressed in percent of rated kilowatts per second. For example, if a
change of load of 50% is required and the rate set for 10% per second, the change
takes 5 seconds to complete. The CGCM unit has an internal relay that isolates
the load share circuit whenever the function is not active or when control power
is not present.
Metering
The CGCM unit provides true RMS metering based on voltage and current
samples obtained from the current and voltage inputs. All monitored parameters
are derived from these values. Accuracy is specified as a percentage of full scale, at
25 °C (77 °F) across the frequency range of the controller, at unity power factor.
Metered parameters are communicated to the host Logix programmable
controller via the Unscheduled Read table.
The Metered Parameter Accuracy table lists all metered parameters and their
accuracy.
3-phase generator side metering is independent of the Synchronization mode in
one or two breaker schemes. In the two-breaker scheme, single-phase bus side
metering is provided only for the selected bus.
Refer to the Specifications, Appendix D , for information on metering accuracy.
Refer to Power System Sign Conventions on page 66 for the sign convention of
power and current values.
Metered Parameters
The CGCM unit provides the following metered parameters. The collection of
metering data is dependent on the metering wiring mode selected, for example,
single-phase, open-delta, four-wire wye, and three-wire wye.
IMPORTANT
Series B units do not isolate when control power is lost. An external relay
must be used.