Slow Blow Fuse??

[Terry G]

The Hypertherm 1000 manual states to use a slow blow fuse. I spoke with their tech support and they recommended a 60A slow blow fuse. I currently have a 100A disconnect switch with class H fuses to run my Tig welder. I have a 60A box that accepts Class H, K5 style fuses which I am connecting after my 100A switch. I was going to run the standard off the shelf 60A NON class K5 style fuse. Will this be a problem? Or do I absolutely need this slow blow fuse which I can't seem to find anywhere. Are slow blow the same thing as Time Delay fuses?

So what do others run for thier 60A plasma cutters?

Thanks.

[kreutz]

Are slow blow the same thing as Time Delay fuses?

Yes, they are.

[Terry G]

Thanks!

Has anyone used a non time delay fuse with the plasma cutters? I'm guessing the plasma cutters have a surge current that may blow a standard fuse. Though I don't know how thick of material I would need to cut to reach a 60A load.

[kreutz]

Sometimes it is the "power on" inrush current the one that blows fast fuses, many of the new inverter type equipment charges directly a bank of capacitors from the line (1 or 3 phase) through a bridge rectifier. This initial charging current can blow the non "time delay" fuses.

The surge is limited when the manufacturer uses a current limiting resistor in series with the rectifiers which is bypassed by a relay when certain voltage is reached at the capacitor bank or after a time delay.

Better designed equipment will have a soft-start controlled rectifier circuit or Power factor correction circuit which control the surge current.

[Terry G]

I found some 50A time delay fuses to fit my box. I went with the 50A since my receptacle is rated at 50A. Unless I am cutting 1" thick steel all day long, I don't think I should have a problem.

Thanks for the info.

[SCouch]

Time delay is the same thing as slow-blow. They are available at any electrical supply house, but you probably won't find them at a hardware store or lumber yard like Lowes or Home Depot.