Question on CP200 conversion individual AC coil voltage output.

Hello All
I've been running my converted Miller CP200 for some time now and it's been performing well.
Today I decided to remove the side panels and blow out the accumulated dust. So after a through cleaning I decided to take out my multi meter and perform a variety of voltage checks. So it being a three phase transformer with three individual coils I went about testing each coil's AC voltage output. What I found is the center coil which runs through two motor run capacitors was only putting out half the AC voltage of the two outer coils, for example each outer coil tested at approx. 24VAC the center coil showed only approx. 12VAC.
Is this normal and to be expected? Since the center coil is running through the two capacitors? Or should all three coils be testing at approx. the same voltage?

Miller CP200 low or no output from "B" phase coil

jzr75601 said:

Hello All
I've been running my converted Miller CP200 for some time now and it's been performing well.
Today I decided to remove the side panels and blow out the accumulated dust. So after a through cleaning I decided to take out my multi meter and perform a variety of voltage checks. So it being a three phase transformer with three individual coils I went about testing each coil's AC voltage output. What I found is the center coil which runs through two motor run capacitors was only putting out half the AC voltage of the two outer coils, for example each outer coil tested at approx. 24VAC the center coil showed only approx. 12VAC.
Is this normal and to be expected? Since the center coil is running through the two capacitors? Or should all three coils be testing at approx. the same voltage?

Click to expand...

Also after welding a few minutes the "A" and "C" phase coils are warm to the touch while the "B" phase is cold to the touch.
Any help would be greatly appreciated.

That depends entirely on loading. If you're not working it hard, the center won't be carrying much... and when you work it harder, it will carry MORE. What happens when you weld for a few more minutes at a higher setting? Does it rise in temperature? Add 10uf to each leg, and try it again...

But don't worry about the voltage... it is not the job of the welding machine to give you a voltage reading, it's the machine's job to give you deep penetration, and a nice clean, workable puddle to marry two pieces into one.

Hello Dave and thank you so much for the reply
I did raise the output a bit, I was around 38VDC on the front panel indicator and still no discernable rise in temperature.
I'm using two cap's rated at 60uf 370VAC. I will try adding more capacitance. Thank you for clarifying in regards to the center phase only really starts to work at a higher out put, that helps out a lot! It does weld well, I was just thrown off by probing around .

What it really comes down to, is that WITHOUT the center coil having some amount of phase-shifted 'drive', the center segment of the transformer becomes a big parasitic loss. Once you allow compliance, it starts to circulate, which causes the outers to become much more efficient, and the INNER starts doing work.

Two things cause heat in a transformer: first, is resistance through the windings, the second is eddy currents in the core.

In an AC circuit, you can have a high current flow, but very low voltage... and you can have a very high voltage, with no current. This is the result of a series- or parallel-resonant circuit, so don't get too caught up in coil voltages on either the primary or secondary side. It isn't a machine to develop specific voltages, it's a WELDER. What's important, is how well it's doing the WELDING task.