Technical specifications
6.4 Derating and temperature compensation
3VA molded case circuit breakers with IEC certificate
632 Manual, 03/2019, A5E03603177010-03
Temperature compensation for thermal-magnetic trip units TM210, TM220 and
TM240
The trip units for 3VA1 molded case circuit breakers are factory-calibrated to a temperature
of 50 °C. The thermal response threshold of the trip unit changes when the circuit breaker is
operated in a higher or lower ambient temperature. To obtain the characteristic tripping times
at a specific ambient temperature, it is necessary to apply correction factors when setting the
thermal trip units.
Correction factor TK is applied to compensate for the ambient temperature.
The first step in calculating the correction factor TK is to determine the setting factor at 50 °C:
EF(50 °C) Setting factor at 50 °C
I System current
I
n
Rated operational current of the molded case circuit breaker
Using the setting factor calculated at 50 °C, it is possible to read the correction factor K off
the following charts:
No derating up to the rated operational current I
n
of the molded case circuit breaker
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