Manual

44 Rockwell Automation Publication 1407-UM001G-EN-P - April 2013
Chapter 3 CGCM Unit Operation
Excitation Control Modes
The CGCM unit controls the DC excitation current of the generator exciter
based on a number of factors, including the following:
• The selected control mode
• The configuration of the CGCM unit including gains
• Measured generator voltage and current
• The applicable setpoint or setpoints
• The value of the Auxiliary Input
• Various limiting functions
The CGCM unit offers several modes of regulation that are selected and
activated by using the software interface to the host Logix programmable
controller. An active ControlNet network connection must exist with the host
Logix controller for any regulation mode to be active.
The CGCM unit automatically shuts down excitation if one of these faults
occurs:
• Overexcitation voltage
• Reverse VAR
• Logix controller fault
Gains
The CGCM unit regulates excitation current by using a proportional, integral,
and derivative (PID) control algorithm. The regulatory response of the CGCM
unit is determined by your gain settings. The gains for each mode include the
following:
• Proportional Gain Kp – determines the basic response to changes in
generator voltage
• Integral gain Ki – speeds the return to steady state voltage after a
disturbance
• Derivative gain Kd – speeds the initial regulator response to a disturbance
• Overall gain Kg – adjusts the coarse loop gain of the regulator
• Auxiliary Gain – adjusts the effect of the auxiliary input on the regulator
output
Please refer to Chapter
4, CGCM Unit Configuration, for more detailed
information.