Quick Fault Current Calculator

I _f.l. = Full Load Amperes
I _S.C. = Short Circuit Current
KVA = The KVA of your transformer, or bank of transformers
% ML = Percent Motor Load
E _L-L = Voltage Line to Line
Z = Impedance
100 / Z = Multiplier

Three Phase Calculations:
(KVA X 1000) / (E _L-L X 1.732) = Three Phase Full Load Amps, I _f.l.
100 / Z = Multiplier
I_f.l. X Multiplier = Transformer let thru Short Circuit Current, I _S.C.
4 X FLA X % ML = Motor Load Contribution to Fault Current, I _{S.C. motor cont.}
I _S.C. + I _{S.C. motor cont.} = Total Short Circuit Current, I _{S.C. Total}

Single Phase Calculations:
(KVA X 1000) / E _L-L = Single Phase Full Load Amps, I _f.l.
100 / Z = Multiplier
I_f.l. X Multiplier = Transformer let thru Short Circuit Current, I _S.C.
4 X FLA X % ML = Motor Load Contribution to Fault Current, I _{S.C. motor cont.}
I _S.C. + I _{S.C. motor cont.} = Total Short Circuit Current, I _{S.C. Total}

KVA
E _L-L
Z
% ML

Source for Formulas: Cooper Bussman Short Circuit Calculations PDF