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Transformer short-circuit current (estimate)

Maximum secondary fault current from kVA and impedance.

kVA
V
%
On the transformer nameplate

Calculating…

How it's calculated

I_FL = kVA × 1000 ÷ (√3 × V) I_sc = I_FL × 100 ÷ Z%

This "infinite source" estimate ignores the supply network and cable impedance, so it gives the worst-case (highest) current at the transformer terminals. Real fault current further out on the system is lower.

Use this for a quick sense check only. Protective device ratings and arc-flash studies need a proper fault-level calculation by a competent person.