Keep my MP-45E and RPC, Haas Kamp, or sell?

Hey there,

I am somewhat new here (and pretty new to welding as well). I picked up a MP-45E Generator, and a Millermatic D-52A (Not S) wire feeder for a somewhat good price. Right now, my home doesn't have 3 phase power (Canada, sigh...) but I do have 240V 400A available to me due to an uncompleted addition. Pretty much my question is: Since I don't have 3-phase, should I sell it (and make a small profit), try to convert it (I believe it has been done before), or build a rotary phase convertor? I have the electrical skills to complete the last 2 (I work construction, and high voltage mains is just something I deal with), so what do you think? Is it a worthwhile machine to keep? Thanks!

Hi Trend-

You don't note which serial range your MP-45 shows, but I took a random pick of the mid-series, and downloaded the manual (OM-227) from Miller, looking at page 11, your MP45E appears to have a 230/460 delta input on the main transformer, and a single-phase 230/460 on the control transformer.

Converting this one for 240 single phase would be very simple... basically the same as the SRH-333, it even uses magnetic amplifier control.

Set the main and control transformer jumpers to 230v, separate the delta connections, add phase shift capacitors to the center winding, connect the outer coils 180 degrees out of phase, and the capacitors' feeders however (doesn't matter which way).

As unobtrusive as it is, a conversion trial FIRST, and if after a little experimentation, you don't like, then set it back.

It's a beastly horse, you WON'T easily overrun it's capacity or duty cycle. I doubt very much that you'll find a machine with it's durability or duty cycle for under $3500CDN...

Hi there,

Wow! Thank you for the response! I honestly never would've expected you to be doing it haha. The machine was produced in Quebec and purchased around 1983, the problem is that the serial number doesn't match anything close to Millers site (or manuals). I've contacted them and I am currently awaiting a response. I definitely will be holding onto it if the conversion is possible, I wanted a project and it looks like I got it! Is there a way to calculate the uF of the capacitors I'll need, or is it trial and error? Thank you!

EDIT: Changed trail to trial

Yeah, the Canadian-built Millers used different serial number series... (they were all in French, eh!)

The way you determine proper UF, is get into the ballpark, then do some test welds at different current levels, and make adjustments to suit the best results.

With your machine being magnetic amplifier control, it's hard to say how it'll respond. Look at my SRH-333 writeup on it, as it's pretty darned close- it's a Constant Current (rather than Constant Voltage) machine, but it's 230 Delta, and uses mag amp. I would be inclined to bet that following that one would get you about the same result. I KNOW that you'll be needing a bit more capacitance than the CP-series. If it were ME doing it, I think I'd start around 80uf, and add another 10 or 20 to see how it responds.

I WILL note here that when I was volleying photos of my napkin-drawings to Peter, my math was appropriate, save for one basic overlook- I did my original calculations assuming 60hz, but that was improper- since I was operating in quadrature, the actual operating frequency was HIGHER (it was alternating every 90 degrees, rather than every 60 degrees. This means that it likely won't require as much capacitance as the math I noted implies. The real thing to remember, however, is that was an estimation based solely on a WAG... I did not have any 'good' data on inductance or reactive load, I was basically swatting a baseball out far, with the hopes of being able to 'tell which way the wind was blowing'. I didn't need precision, and it's a good thing... because every OTHER machine out there, has a little different transformer character, some needed a little more, or a little less, and some simply didn't care- once there was a capacitor in there, it went straight to work.