SHORT-CIRCUIT CONTRIBUTION
SHORT-CIRCUIT CONTRIBUTION
(OP)
We are making a short-circuit calculation now, for industrial plant, and needs information about considerations of contribution of high power motors using soft-starters (without by-pass contactors)during short-circuit time. The question are: We need consider its contribution for short-circuit current in the switchgear bus or not?
Thanks
Thanks






RE: SHORT-CIRCUIT CONTRIBUTION
First, it may be as easy as checking with the soft-start manufacturer. Second, most soft-starts have two SCRs in parallel per phase, each conducting in the opposite direction. Once the motor is at full voltage, the SCRs are gated on all the time and in principle there is nothing to stop a reverse current from flowing back to the source, unless the soft-start has internal protection that would prevent this scenario.
RE: SHORT-CIRCUIT CONTRIBUTION
I know of no soft starter manufacturers that offer reverse flow protection, nor can I think of how we would do it.