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
3
3.2.10 POWER FACTOR REGULATION
Power factor regulation is useful in those applications where motors are subjected to high-level transient
impact loads (such as chipper drives). The PF regulator senses the power factor dip that occurs when the
motor is loaded and causes the SCR Exciter to respond with a boosted output. As a result, the pull-out torque
of the synchronous motor is increased for the duration of the transient load. After the load subsides, the regu-
lator senses an excessive leading power factor and causes the SCR to reduce its output. This automatic boost-
ing of field current to avoid pull-out is called field forcing. The Power Factor regulator thus provides automatic
boosting when field forcing is required and economical low field operation when the motor is idling.
Another application of the power factor regulator is to control power factor swings that result from various lev-
els of loading so as not to cause fluctuations in the plant system voltage.
The SPM provides the control signal to the variable SCR exciter when PF regulation is required. See the fol-
lowing figure for a functional operation overview of this feature.
Figure 3–13: POWER FACTOR REGULATION
701754A4.CDR
A
B
C
MOTOR
PF
Detection
Voltage
Input
Field
DC Supply to
Motor Field
PF
Setpoint
Reg
Output
Reg
Gain
Reg
Stability
Reg
Floor
Current
Input
PF
Feedback
Control
Signal
SCR
Proportional
Exciter
SPM
Field
Contactor
Main
Contactor
PF
Regulator