Siemens SINAMICS S120 Combi User Manual page 34

Line-side power components
2.3 Overcurrent protection by means of line fuses and circuit breakers
Information on the tripping time of line fuses
In order that the line fuses trip in a timely manner, the loop resistance as well as the vector
group of the feeding line transformer must ensure that, if a fault occurs, the touch voltage of
the devices is disconnected by the fuses provided within the permissible tripping time (see
figure below, in accordance with EN 61800-5-1 Ed. 2).
Figure 2-2 Permissible tripping time of fuses
The boundary conditions indicated above also serve to avoid a fire in case of a fault. If you
do not comply with these boundary conditions, you must take additional measures, e.g.,
residual current transformer.
Fuse and plant conditions such as loop resistance and short-circuit power must be
harmonized to one another so that the limit curve is not exceeded. This guarantees the
shock-hazard protection.
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SINAMICS S120 Combi
Manual, Edition 07/2012, 6SL3097-4AV00-0BP3