GE SPM Series, Instruction Manual

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SPM Synchronous Motor Protection & Control GE Power Management
3.2 COLLECTOR-RING MOTORS 3 SYNCHRONOUS MOTOR APPLICATIONS
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3.2.7 CONTROLLER ACTION DURING PULL-OUT
If excessive mechanical load is applied to the motor shaft during normal running of the motor in synchronism,
the resulting lagging power factor and/or line current surge will be detected by the SPM. Two forms of pull-out
protection are available. They are as follows
a) RESYNC MODE
Resync mode operation causes the Field Application Relay, FAR, to remove the motor-field excitation. Action
will occur from either lagging power factor below the programmed setpoint or a line current surge above
approximately four times motor full-load current.
Relay FCX drops out at the same time as FAR. Load is removed if an automatic loader is connected.
The motor will continue to run with field removed for the programmed power factor delay time, and if resyn-
chronization does not occur within this time, the TRIP relay will operate and the motor will stop.
The display will indicate "FAIL TO RESYNC!"
b) RIDE-THRU MODE
If the alternate "ride-thru" mode is selected, the field is not removed immediately as in the resync mode.
Instead, if the power factor dips below the trip point and persists for the PF time delay, the TRIP relay will oper-
ate and the motor will stop. Also, a line current surge greater than approximately four times motor full load will
cause TRIP operation if the PF time delay is exceeded. Power factor trips are indicated by "PWR FACTOR
TRIP!" in the display. Line current surges greater than four times rated line current are indicated by "PULL-
OUT TRIP!".