hager hw+ User Manual

50 6LE008146B
Protection functions
4.1 Long time delay protection against overcurrent
The tripping time tolerance for the long time delay overcurrent protection is from 0% to
-20%.
Example:
For tr = 5 s and I = 6 x Ir, the tripping time for long time delay overcurrent protection will be
between 3.98 s and 5.03 s.
Thermal image
Closure resulting from an overload, successive motor starts or a fluctuating load cause
significant current swells that can potentially damage conductors (heating up, premature
ageing).
Traditional Long time delay protection is not able to protect the conductors against repetitive
faults of this kind because the duration of each detected overload is too short to cause
eective tripping.
Thanks to its thermal memory and imaging function, the sentinel Energy trip unit memorizes
and integrates the thermal eects of the detected overloads whatever the current value. These
functions are guaranteed even if the trip unit is not powered by an external power supply. This
reduces the associated Long time delay time to cause eective tripping before the conductors
overheat.
The thermal memory and image function of the sentinel Energy trip unit provides optimal
protection of the cables and busbars against overheating.
Tripping threshold
a)
c)
b)
I
1)
t
2)
Tripping with and without thermal image
Key:
a) Calculation with thermal memory
b) Calculation without thermal memory
c) Instantaneous current in the load
1) Tripping case a)
2) Tripping case b)
The example above clearly shows that the trip unit a) with thermal memory trips earlier and
thus protects the conductors better than trip unit b) without thermal memory.
N.B.
The thermal imaging function of the sentinel Energy trip units cannot be deactivated.

hager hw+ Specifications

General

Brand	hager
Model	hw+
Category	Circuit breakers
Language	English