Siemens 3VA1 100 A, Manual

Page: 494 / 532

Technical specifications
6.4 Derating and temperature compensation
3VA molded case circuit breakers
494
Manual, 04/2015, A5E03603177010-02
Example 2: Calculation of the tripping time
Starting point:
Based on the example above, the tripping time for an overcurrent I
O
= 360 A will now be
calculated.
To compensate for the ambient temperature of 60 °C, rather than 50 °C, the thermal trip unit
has been set I
r(60 °C)
= 95 A for a system current I = 90 A.
The first step is to calculate the ratio between the overcurrent and the system current:
I
o
/I = 360 A / 90 A = 4
Using this value, it is now possible to read the tripping time from the characteristics chart:
①
Tripping time (schematic representation)