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5.7.2
Overload Alarm
OVERLOAD
5.7.3
Mechanical Jam
MECHANICAL
5–60
be increased if nuisance tripping occurs.
When a motor starts, the starting current (typically 6 × FLA for an induction motor) has an
asymmetrical component. This asymmetrical current may cause one phase to see as
much as 1.6 times the normal RMS starting current. If the
set at 1.25 times the symmetrical starting current, it is probable that there would be
nuisance trips during motor starting. A rule of thumb has been developed over time that
short circuit protection at least 1.6 times the symmetrical starting current value. This
allows the motor to start without nuisance tripping.
The overreach filter removes the DC component from the asymmetrical current present at
the moment of fault. This eliminates overreach; however, the response time slows slightly
(10 to 15 ms) but remains within specification.
PATH: SETTINGS
S6 CURRENT ELEM.
[
MESSAGE
MESSAGE
MESSAGE
If enabled as "Latched" or "Unlatched", the Overload Alarm functions as follows. After a
motor start, when the equivalent motor heating current exceeds the
, an alarm will occur. If programmed as "Unlatched", the overload alarm resets itself
LEVEL
when the motor is no longer in overload. If programmed as "Latched", the
be pressed to reset the alarm once the overload condition is gone. Event recording for all
alarm features is optional.
For example, it may be desirable to have an unlatched alarm connected to a PLC that is
controlling the load on a motor.
PATH: SETTINGS
S6 CURRENT ELEM.
[
MESSAGE
MESSAGE
MESSAGE
OVERLOAD ALARM
OVERLOAD
ALARM: Off
ASSIGN ALARM
RELAYS:
OVERLOAD ALARM
DELAY: 0.1 s
OVERLOAD ALARM
EVENTS: Off
MECHANICAL JAM
MECHANICAL JAM
TRIP: Off
ASSIGN TRIP
RELAYS:
MECHANICAL JAM
PICKUP: 1.50 x
MECHANICAL JAM
DELAY: 1 s
469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
SHORT CIRCUIT TRIP PICKUP
Range: Off, Latched, Unlatched
Range: Alarm, Auxiliary2, Auxiliary3,
Alarm & Aux2, Alarm & Aux3,
Aux2 & Aux3, Alarm & Aux2 &
Aux3
Range: 0.1 to 60 s in steps of 0.1
Range: On, Off
OVERLOAD PICKUP
key must
RESET
Range: Off, Latched, Unlatched
Range: Trip, Trip & Auxiliary2, Trip &
Aux2 & Aux3, Trip & Auxiliary3
Range: 1.01 to 3.00 x FLA in steps of
0.01
Range: 1 to 30 s in steps of 1
was
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