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Chapter 3
CGCM-DLR Unit Operation
56
Over-excitation Limit
The Over-excitation limit (OEL) operates in all modes except FCR. The
CGCM-DLR unit senses and limits the field current to prevent field
overheating. When the limit is reached, the limiter function overrides AVR,
VAR, or Power Factor modes to limit field current to the preset level. OEL
operates in the area above the Field Winding Heating Limitation curve in the
generator capability curve.
The generator operates in one of two different states, offline or online. The
generator is offline when it is operating in a constant-voltage mode. The
CGCM-DLR unit is considered online if any of these modes are enabled:
• Droop (reactive power) compensation
• Cross current compensation
• Line drop compensation
Two OEL current levels, high and low, are defined for offline operation as shown
in
Figure
32. The generator can operate continuously at or below the low OEL
current level and for a time at the high OEL current level that you configure.
Figure 32 - Offline Over-excitation Limiting
Rockwell Automation Publication 1407-UM002B-EN-P - February 2019
High
CONTINUOUS
Current
Time
0...10 seconds
TIME IN SECONDS
High
Current
Level
Low
0...30 A dc
Current
Level
0...15 A dc
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