hager hw+ User Manual

74 6LE008146B
Advanced protection functions
5.7 Current unbalance protection (UNBC-46)
The current unbalance protection (UNBC-46), ANSI 46 permanently monitors the current
unbalances of each phase. When the unbalance is detected on one of the phases, the UNBC-
46 protection allows an alarm to be generated or the circuit breaker tripped.
The unbalances in phase currents generate significant heating and braking torques that can
cause the motor to degrade prematurely.
Current unbalance protection is recommended for motor protection.
Operating principle
Current unbalance protection calculates the current unbalances for each phase, in relation to
the average current, expressed as a percentage:
I
avg
=
I
1 +
I
2 +
I
3
3
I
nba
p
[%] = 100
I
p
- I
avg
I
avg
*
avec p = 1, 2, 3
It compares the maximum current unbalance value to the activation threshold for the
protection.
Example of maximum positive unbalance on phase 2:
I1 I2 I3 Iavg
I1 - Iavg
<0
I2 - Iavg
>0
I3 - Iavg
<0
If the maximum current unbalance is greater than the activation threshold, the protection trips
at the end of the activation threshold.

hager hw+ Specifications

General

Brand	hager
Model	hw+
Category	Circuit breakers
Language	English