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CGCM-DLR Unit Operation
Chapter 3
Internal Tracking
The CGCM-DLR unit provides a tracking function between the non-active
modes of operation and the active mode of operation. This function minimizes
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-DLR
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-DLR 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. When the mode is changed, the regulator
begins changing its operating point from the internal tracking setpoint to the new
mode setpoint. The new mode traverse rate determines the change rate.
See
Chapter 4
for information on scaling and units of the traverse rate settings.
An increasing traverse rate causes the regulator output to change more slowly. A
value of 200 seconds is a special case that causes the CGCM-DLR unit to hold
the existing regulator output until the new setpoint is adjusted to become equal
to or pass through the previous mode setpoint.
The tag SetptTraverseActive = 1 when the CGCM-DLR unit is traversing
between the internal tracking setpoint and the new operating mode setpoint. The
tag = 0 when the operating point has completed traversing to the new mode
setpoint. This tag is used by the host Logix controller to determine when the new
mode has taken control.
Rockwell Automation Publication 1407-UM002B-EN-P - February 2019
53
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