I know this is a bit off track for this site but any advice would be helpfull. I have a 312amp motor on a centrifical compressor. It is controlled by a smc softstarter. It has a very high enercia load and takes quite a long time to start. It pulls 2860amps for 2sec ,then 1500amps for 10 sec, then 2600amps for 1 sec when the starter applies full voltage. The supply fuse is a TTM500 HRC. On a time vers current graph it shows that the fuse can only hold approx 3000amps for 5sec. What i thinks is happening is that over a period of time these fuses are degrading and failing. The 3 fuses have blown one after the other ie a ,b,c over approx 1.5 years use. This has happened only in the last 2 months. Even if the fuse can handle the current can they fail like this? Going to a larger fuse will give another 5 sec or so(for a 630amp fuse) however the cable,main isolator(500amp) and main feed are not large enough. Would a better option be to install a circuit breaker with adjustements to get passed this high starting currents?
