Rockwell Automation 1407-CGCM Combination Generator Control Module - Manual (Page 189)

Rockwell Automation Publication 1407-UM001G-EN-P - April 2013 189
CGCM Unit Math Models Appendix B
Figure 65 - Per-unit Block Diagram for Over-excitation Limiter
Figure 66 - Over-excitation Limiter Reference
V/Hz Limiter V/Hz limiter is designed to protect the generator and step-up transformer from
damage due to excessive magnetic flux resulting from low frequency operation
and/or over-voltage.
V/Hz limiter has been designed with an adjustable slope (K
V/HZ
) from flat to
3 pu V/Hz. When the system is in an under-frequency condition, the voltage
reference is adjusted by the amount calculated based on two programmable
parameters, the corner frequency and the V/Hz slope. Its mathematical model is
shown in V/Hz Limiter.
Figure 67 - V/Hz Limiter
Reference Field Current (I
OEL_REF
)
Count Down For Reset
Time (s)