VFD/3ph Welder question?

Anyone know if a VFD can safely (without blowing itself out) run a 3ph welder?

Ive a 25hp older VFD, which appears to be unused, and a 300 amp 3ph MIG welder.

Is it possible to run the welder, from the VFD, from single phase power, without blowing out the VFD?

Id have to say it would smoke the VFD..but..Im not particularly knowlegeable about this aspect of VFDs.


Reply to
Gunner Asch
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Gunner -

I suspect you would be driving a transformer in the welder. Surges - starting and stopping would be buffered by the magnetic core of the transformer.

The core is likely intended to be a 50/60 Hz core and dumping full wave alternate frequency would have varying power levels due to the frequency response of the transformer. It might have good response to react to the torch needs so it might work just fine.

It would be like using the VFD on a motor that wasn't designed for different frequencies. Some work ok and some don't.

Mart> Anyone know if a VFD can safely (without blowing itself out) run a 3ph > welder?

Reply to
Martin H. Eastburn

Now the big question is...will it smoke the VFD if I try it?

This particular vfds are going for $500+ on ebay..and Id rather sell it in good working order, than dump it in the trash can.

Its similar to this one, but 220vt and 25 hp

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Reply to
Gunner Asch

Transformers do not like to operate at frequencies lower than what they are designed for. They are designed for a ET ( voltage times Time ). So if the VFD ramps up the motor over about ten seconds, I do not think it will work. The VFD will be applying pulses, but they will be in same polarity, so I think the transformer core will saturate and then act as a dead short in the beginning.

After the VFD is simulating 60 Hz, there will be a lot of higher frequencies present. These will cause more eddy currents than usual.

In short I think you could operate the welder on single phase power , or use a bunch of capacitors ( as the young lad the Iggy sold a three phase welder to did ) or run it off a rotary phase converter. But I am skeptical of running it on a VFD.

=20 Dan

Reply to

Thanks guys. That was pretty much what Id thought, shrug..but it was a question that I had to ask. Chuckle..got this really nice welder..got this really nice but way way too big for anything I need VFD...

Much obliged folks.

Anyone want to buy a really really nice 3ph MIG?


Reply to
Gunner Asch

You'll be wanting to fix the VFD output at 60Hz (50 in the UK). It'll give it's rated output into a motor or a transformer (after all, a motor is a rotating transformer). Don't use the DC injection braking (if it has it)!!!


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