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Max Short-circuit current of Silcon in Battery Operation

Electrical regulations require a UPS to be able to deliver a sufficient current to clear Fuses or MCB’s in the event of a short circuit on the output.

When the system is online this is not an issue as system switches to bypass until fault is cleared. When on battery operation, there is a current limiter which
limits the current to 150% and this would not necessarily be sufficient for the to trip the required protection in the specified time. However we also specify a sub-cycle 300% current limit for fault clearing for the Silcon.

This means that 300% of the max rated current will be supplied for up to 20 mil.sec. (0.02 Sec) If the MCB or Fuse is selected correctly, this will be sufficient to clear the MCB / Fuse.