GE 269Plus

3- 60 269Plus Motor Management Relay GE Power Management
THERMAL MEMORY 3 SETUP AND USE
3
a) U/B INPUT TO THERMAL MEMORY
When U/B input to thermal memory is defeated, the 269Plus will use the average of the three phase currents
for all overload calculations (i.e. any time the overload curve is active). When U/B input to thermal memory is
enabled the relay will use the equivalent motor heating current calculated as shown:
where:
I
eq
= equivalent motor heating current
I
avg
= average of three phase currents
I
FLC
= motor full load current
I
start
= learned motor starting current (average of last 4 starts)
I
p
= positive sequence component of phase current
I
n
= negative sequence component of phase current
Thus the larger the value for K the greater the effect of current unbalance on the thermal memory of the 269
Plus relay.
I
eq
I
avg
(with U/B input to thermal memory disabled; factory preset)=
I
eq
I
p
2
KI
n
2
⋅+ (with U/B input to thermal memory enabled)=
K
175
I
start
I
FLC
⁄()
2
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=