Blowing the MC-1 fuses on my shaper?

[Larry Edgerton]

I am running a 9 hp motor on a Unitronix and started blowing the one amp fast burn fuses on the control panel. Pain in the tush and they are about $15 each, and not available locally. This just cropped up recently, but I have blown 5 now in the last month. The shaper has two motors, but I never run two at the same time.

I am running it off of a 25hp rotary converter, and I suspect that is where it is coming from, but I am no expert, and that is an understatement. I am going to be switching to a Phase Perfect when I can, but for now this is what I have.

Anyway...... any ideas what can cause this problem? Another thing that is strange, it will work all day long, but all of the fuses have been blown when I come in in the morning. shut it down at night, come in to go to work, and nothing. Not every day, and never in the middle of the day.

Larry

[Rod Sheridan]

Larry, I would suggest that you verify that you're not feeding the control circuit from one of the manufactured legs of your converter.

The control circuit will probably have a transformer so it will be fed from 2 phases, make sure these are the same phases as your single phase source, not the manufactured leg.

The other issue is that fast acting fuses aren't normally used on control circuit primary power as transformer or contactor inrush can clear them.

I suggest you verify with the equipment manufacturer the exact part number of fuse that should be used, don't base it on what was in the machine as that may be incorrect.

Regards, Rod.

[Larry Edgerton]

Rod, converter was set up by a pro, not me and it has run this shaper for a couple of years with no issues. Just this last month.

I mis-spoke, the fuses are MCL-1 fuses.