Question for Andy on 3-phase arc quality ??

[tooldude56]

Hi Andy:
I have'nt heard much about it lately,but I used to hear a lot of hype about the smooth 3-phase arc quality in welders with 3-phase input.I thumbed through one of my old Miller catalogs today and I noticed an add for the MM300 and It boasted a smooth 3-phase welding arc.My real question is; What about machines like the XMT and 350P?? Do they have a diminished arc quality when used with single phase input power?? I have had an XMT since 1998,but never have tried to used it with single phase power.I have 3-phase in my shop,so I try to keep as many machines as possible hooked to the 3-phase.I have welded with many inverters,way back to my first Arc-Pak 350,but have never hooked one to single phase power.This is just something that has been laying on the back of my mind for a while and I would be interested to hear what everyone else thinks about this subject.
Thanks
tooldude56

[HAWK]

tooldude56,

Andy's back in town, but still catching up from the trip. The XMT does not care about the input power phase as far as arc quality goes. You get the same stable clean arc on 1 or 3 phase power. As a matter of fact you can actually get the rated 400 amp output running the unit on 1 phase power. However, this does significantly increase the work load on the input rectifier bridge and filter caps. Therefore, the duty cycle on the upper end is effectively reduced to approximately 1/2 the 3 phase rating. For example the 3 phase rating is something like 300 amps at 60% so the same 300 amps output on 1 phase would be rated near 30%.

[ASKANDY]

The inverters you mentioned have no arc differences when hooked to single phase. It's the standard transformer/rectifier units that differ. A 3 phase units when rectified has overlapping current and voltage waveforms where the filter capacitors don't have to work as hard to keep the output smooth. A single phase unit really depends on the caps and stabilizer coils to help smooth the arc.

A