U/B Input To Thermal Memory - GE 269Plus Instruction Manual

THERMAL MEMORY
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:
I I (with U/B input to thermal memory disabled; factory preset)
eq avg
2
⋅
I I K I
eq p
175
where: K
( ⁄
I
start
I
= equivalent motor heating current
eq
3
I = average of three phase currents
avg
I = motor full load current
FLC
I
= learned motor starting current (average of last 4 starts)
start
I = positive sequence component of phase current
p
I = negative sequence component of phase current
n
Thus the larger the value for K the greater the effect of current unbalance on the thermal memory of the 269
Plus relay.
3-
60
Courtesy of NationalSwitchgear.com
2
(with U/B input to thermal memory enabled)
n
)
2
I
FLC
269Plus Motor Management Relay
3 SETUP AND USE
GE Power Management