Is there any information on what a regenerative drive will allow a motor to contribute to an upstream fault? I know ANSI has some standards for motor contributions based on <50HP or >50HP for across the line starters. We have some DC motors with regen drives connected to a 480VAC system and I want to model the contributions of the motors on the upstream switchgear. A few of these motors are 500HP or bigger.

We used to use Easypower and I remember that had an option for selecting if your drive was Regen or Non-Regen, and that would affect the contributions. But the contributions of a regen drive was less than across-the-line for the same size motor.

We've since switched to etap, and their drive model doesn't have a re-gen option. Not to mention they don't have a real clean way to model a DC drive on an AC system.

I'm thinking there's a way I can model the load and the short circuit calculations if there's some sort of impedance multiplier for re-gen drives for the 1/2 cycle or 5 cycle short circuit.

Sorry, but why did you switch to ETAP???

Look in the information on the drive. They will give you a maximum current draw. Worst case, the transistors are rated for RMS ratings so they can't exceed approximately 200% of their maximum name plate ratings or the transistors turn into very fast fuses (blow up).