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3 SYNCHRONOUS MOTOR APPLICATIONS
3.2 COLLECTOR-RING MOTORS
3.2.6 POWER FACTOR OPERATION
Motor pull-out protection is provided by a circuit which monitors power factor and has a built-in time delay to
prevent inadvertent tripping on transients. The SPM senses power factor by monitoring the voltage across
motor Phases One and Two and the current in Phase Three. Figure 20 is a phasor diagram depicting the rela-
tionship of voltage and current for various power factors.
The SPM automatically suppresses power factor protection until the programmed setpoint "FCX" times out.
The SPM can be programmed to suppress power factor trip action if the line current is less than 6 percent or 50
percent of the rated full load current via the PF Suppression setpoint. Selecting the "Ridethru" mode for the PF
Mode setpoint places the SPM into ride-through mode. Selecting the "Re-sync" mode for the PF Mode setpoint
places the SPM into resync mode. These modes are described in the next section.
3
Figure 3–10: POWER FACTOR SENSING EXAMPLE
GE Multilin
SPM Synchronous Motor Protection and Control
3-
11
Courtesy of store.ips.us
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