A small and handy article for all of you working with motors.
"Calculating the short-circuit current across the terminals of a synchronous generator is very complicated because the internal impedance of the latter varies according to time.
When the power gradually increases, the current reduces passing through three characteristic periods:
Subtransient (enabling determination of the closing capacity of circuit breakers and electrodynamic contraints), average duration, 10 ms
Transient (sets the equipment's thermal contraints), average duration 250 ms
Permanent (this is the value of the short-circuit current in steady state)."
Read the rest of the article and the maths here.