3 phase plasma cutter wiring question.

[dsergison]

I just got a free old ESAB PCM-875 400v/460v 3phase plasma cutter.

The cord had been cut off. This is usually a bad sign for a power tool, like there was something wrong with it and it was put out of service, but the price was right. (I did carefully test the chassis and such to make sure it did not have any faults and I wasn't going to shock myself. I wore some arc flash protection for power up and testing etc..)

Upon wiring it with a cord I found that the 3 pole breaker switch on the unit had been wired with 2 phases passing through it and 1 phase bypassing it.

What's up with that? Can there be any good reason to do such? I could not in good conscience wire it up with one un-switched live phase, so I put them all through the switch.

It worked fine as I wired it, but I did pop a 15 amp fuse in the machine cutting at 60 amps, it's max setting. also tripped the breaker.

The schematic CB1 on page 13 does not show any bypassing.

the machine manual
http://www.esabna.com/literature/pl...kages/international/pcm-875_ce_f-15-424-a.pdf

Thanks,
Dan

 

[gbent]

It is possible the machine was used on a corner grounded delta system. As I understand it, the leg that is grounded shouldn't be fused.