GE MI-869 Instruction Manual page 185

CHAPTER 4: SETPOINTS
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869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
to zero, and resets all Trips and Alarms so that a hot motor may be restarted. However, a
Restart Delay inhibit lockout will remain active (it may be used as a backspin timer) and
any trip condition that remains (such as a hot RTD) will still cause a trip.
In the event of a real emergency, the Emergency Restart input must remain asserted
until the emergency is over. All the associated output relays reset until the Emergency
Restart Input is removed. However, the TCU does not remain reset to zero if the
Emergency Restart input remains asserted, the thermal model continues calculating the
TCU.
The Emrg Restart Alarm operand is asserted if the Emergency Restart input remains
asserted for 10 seconds.
NUMBER OF STARTS TO LEARN
Range: 1 to 5 in steps of 1
Default: 3
This setting selects number of motor start and stop records to calculate learned data
presented in the Setpoints > Records > Motor Learned Data.
LOAD AVERAGE CALC. PERIOD
Range: 1 to 90 min in steps of 1 min
Default: 15 min
This setting adjusts the period of time over which the average motor load and power is
calculated. The calculation is ignored during motor starting.
SWITCHING DEVICE TYPE
Range: Breaker, Contactor
Default: Breaker
This setting specifies the type of switching device installed to Stop/Start motor.
MOTOR LOAD FILTER INTERVAL
Range: 0 to 32 cycles in steps of 1 cycle
Default: 0 cycles
This value (when non-zero) averages current and power factor for the programmed
number of cycles using a running average technique.This setting is intended for use on
driving reciprocating loads or variable frequency drives (VFD).
With the reciprocating load application, the number of cycles to average can be
determined from current waveform capture using the Oscillography/Datalogger
features in 869. The second way to determine this setpoint is by using the following
relation:
N = P / 2, where N is the number of cycles to average and P is the number of poles on the
motor.
For example: Set the "Motor Load Filter Interval" equal to 3 cycles for a motor driving
reciprocating load with 6 number of poles.
The latter approach of determining the cyclic load only applies to the applications where
loads are coupled directly to the motor (with no gear box).
When set greater than one cycle, Motor Load Filter Interval may increase trip/alarm times
for the following protection elements: Acceleration Time, Current Unbalance, Mechanical
Jam, Overload, Thermal Model, Undercurrent, Power Factor, Three-Phase Apparent Power,
Three-Phase Reactive Power, Three-Phase Real Power and Under Power. No other
elements are affected. Trip/alarm times increase 16.7 ms (or 20msec @50Hz) for each
additional cycle in the filter interval. The details are described in the VFD section.
SYSTEM
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