Allen-Bradley 1407-CGCM, User Manual, Page: 192 / 252

Rockwell Automation Publication 1407-UM001H-EN-P - November 2014
!PPENDIX" CGCM Unit Math Models
The operating characteristics are designed to mimic the characteristics of the
limiter on the P-Q plane. The desired UEL curve is generated based on the user
input points.
Typical UEL reference is illustrated in Under-excitation Limiter Reference .
&IGURE0ERUNIT"LOCK$IAGRAMFOR5NDEREXCITATION,IMITER
&IGURE5NDEREXCITATION,IMITER2EFERENCE
Per-unit Block Diagram for Over-excitation Limiter shows the model of the
CGCM over-excitation limiter (OEL). The OEL makes up the inner loop of the
voltage regulator and uses a PI type controller. In this control scheme the actual
field current is compared with a reference field current. The operating
characteristics are designed to mimic the field current short-time overload
capability given in ANSI standard C50.13-1977. The reference field current is
calculated based on the user input parameters as shown in
Over-excitation
Limiter Reference .