Siemens 3VA1 100 A Manual page 495

Inclusion of accessories
None of the accessories from the extensive range available for 3VA1 molded case circuit
breakers has an influence on the thermal response thresholds of the switching devices
except for two accessories that require additional correction factors. These are:
● Plug-in version / draw-out version
● Residual current devices
None of the other accessories has an influence on the thermal response thresholds of trip
units.
The table below shows the correction factors of setting value I
molded case circuit breakers in plug-in / draw-out technology and for 3VA1 molded case
circuit breakers combined with residual current devices:
Example
Starting point:
The current loading of a 3VA1 molded case circuit breaker is calculated to be 90 A and the
ambient temperature 65 °C for a given application. The plug-in version of the molded case
circuit breaker will be used.
The appropriate size of molded case circuit breaker is determined first on the basis of the
correction factor for 3VA1 plug-in technology (see table above):
Design of assembly at 50°C: I
It is therefore necessary to select a molded case circuit breaker that allows a setting value of
100 A on the thermal trip unit at a calibration temperature of 50 °C. A 3VA1 molded case
circuit breaker 160 A with I
The temperature compensation is then calculated according to the method described above:
● Ambient temperature 65 °C:
Setting factor EF(50 °C) = (100 / 125) = 0.8
Correction factor K = 0.69 (from chart)
Temperature compensation of switching device TK(65 °C) = (0.69 · (65 °C -
Setting value I
3VA molded case circuit breakers
Manual, 04/2015, A5E03603177010-02
n
50 °C) / 100) + 1 = 1.1
= 125 A · 0.9 · 1.1 = 124 A
r(65 °C)
6.4 Derating and temperature compensation
= (90 A / 0.9) = 100 A
r
= 125 A is therefore used for the application.
Technical specifications
for the trip units of 3VA1
r
495