Correction Factors With Direct Current For The Thermal-Magnetic Trip Units Of 3Va1 Molded Case Circuit Breakers - Siemens 3VA1 100 A Manual

Technical specifications
6.4 Derating and temperature compensation
6.4.5 Correction factors with direct current for the thermal-magnetic trip units of 3VA1
molded case circuit breakers
With DC systems, a correction factor must be applied to the magnetic trip unit.
Where ambient temperatures differ from the calibration temperature, temperature
compensation as described in chapter Derating of 3VA1 molded case circuit breakers
(Page 489) must be performed.
Example:
Starting point:
A 3VA1 molded case circuit breaker 160 A with a TM240 trip unit is used in a DC system.
The molded case circuit breaker is required to trip instantaneously in response to an
overcurrent of 1200 A.
The setting value for the instantaneous short-circuit protection (I
I = 1200 A · 0.7 = 840 A
i
498
) is:
i
3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02