Rockwell Automation 1407-CGCM Combination Generator Control Module User Manual
Page 49
Rockwell Automation Publication 1407-UM001G-EN-P - April 2013
49
CGCM Unit Operation Chapter 3
If the generator is not up to speed when the soft start begins, the voltage increases
but only to the level determined by Volts/Hz limiting. When the unit is operating
in FCR mode, soft start operates as it does in the AVR mode, with the field
current, rather than the generator voltage, being the controlled parameter.
To activate soft start mode:
• the Soft Start Initial Voltage (tag SoftStart_InitLevel) and Soft Start
Time (tag SoftStartTime) parameters must be set.
• excitation enabled (tag SoftwareExcEn = 1).
• remote Excitation Enable On (discrete input).
• FCR mode not active (tag AVR_FCR_Select = 0).
• engine idle bit is set (tag EngineIdle = 1).
Internal Tracking
The CGCM unit provides a tracking function between the non-active modes of
operation and the active mode of operation, to minimize the potential for
instability that can occur when switching from one mode to another. There are
two settings you can configure. The internal tracking rate defines the time
constant of a first-order filter through which the CGCM unit matches the
non-active modes with the active mode and is scaled in seconds. The time for the
tracking function to settle out after a step change in the operating setpoint is
approximately four times the internal tracking rate setting.
The internal tracking delay setting adjusts the delay of the tracking function to
prevent a non-active mode from being adjusted into an undesirable condition.
For example, with AVR mode active, if the generator sensing VT fails open, the
excitation output goes to a full-on state. Applying a tracking delay reduces the
likelihood of this undesirable operating point being transferred to a new
operating mode.
Traverse Rates
You can control the speed at which the CGCM unit switches from one
regulation mode to another by configuring traverse rates for each regulation
mode. These settings define the rate at which the system changes to the new
setpoint when the mode changes. At the instant the mode is changed, the
regulator begins changing its operating point from the internal tracking setpoint
to the new mode's setpoint at a rate determined by the new mode's traverse rate.
Please refer to
for information on scaling and units of the traverse rate
settings.
Increasing a traverse rate causes the regulator output to change more slowly. A
value of 200 seconds is a special case that causes the CGCM unit to hold the
existing regulator output until the new setpoint is adjusted to become equal to or
pass through the previous mode's setpoint.