Stall Protection; Power Factor (Pull-Out) Protection; Power Factor Regulation - GE SPM Series Instruction Manual

3 SYNCHRONOUS MOTOR APPLICATIONS
Stall protection is derived from stator current inputs from two lines feeding the motor. The protection character-
istic is shown in Figure 3–15: BRUSHLESS STALL/ACCELERATION CHARACTERISTIC on page 3–18. After
the motor synchronizes, the SPM monitors motor cool down approximately every 20 minutes rate to provide
protection against motor abuse from too-frequent starting. The SPM will indicate on the display the required
wait time period that must be allowed before attempting a restart on a motor that has been shutdown from a
stall protective operation, or one in which two or more rapidly successive start/stop operations have been per-
formed.
The power factor protection for brushless control operates as power factor protection for collector-ring motors
described in Section 3.2.6. However, current I
rents at the I and I
inputs.
1 2
It is important to connect current inputs for I
machines.
NOTE Only the ride-through mode is available for brushless machines. If an attempt to resynchronize is
desirable, set the "PF trip delay" parameter for one or two seconds. If the motor slips a pole in this
condition, the rotor-mounted, control device will remove the field instantaneously. When, and if, the motor
recovers from the disturbance, the main field will be applied. If it does not recover within the "PF trip time delay"
the motor will trip.
If no attempt to resync is desirable, set the "PF trip time delay" parameter to 0.1 second. This time will be too
short for the power factor to recover following a slipped pole condition and the motor will trip on lagging power
factor.
Power factor regulation is not recommended on brushless machines due to instability problems arising from
the long time constant of the rotating exciter field.
GE Power Management
is derived internally to the SPM by algebraically summing cur-
3
SPM Synchronous Motor Protection & Control
3.3 BRUSHLESS CONTROLLER

3.3.4 STALL PROTECTION

3.3.5 POWER FACTOR (PULL-OUT) PROTECTION

and I
as shown in Figure 8 for brushless
1 2

3.3.6 POWER FACTOR REGULATION

3
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