CP252-TS Single phase conversion

I picked up a 2002 Miller CP252-TS power source and have decided to Haas-Kamp it. I was a bit up in the air about it until I ran it off my friends Rotary phase converter and it welded VERY well, even compared to my Esab Migmaster 250. I have always liked industrial welders, but the three phase has always kept me away from a large MIG machines. My tig machine is a Lincoln Square Wave 355 and that thing is bullet proof and can run at 200A+ for days straight. I sold the Migmaster and am hoping to get this thing running with a good miller feeder (20 or 60 series) for a bit less than I got for my Migmaster.

I have been exchanging emails with Mr. Kamp and he thinks it is very doable especially since its configured in a WYE input very similar to the CP200. I will try to document the conversion well in my thread but quite often I forget to snap pics when I'm in the thick of things.

Here is the wiring diagram based on my serial number:



I put in an order with surplus center for a pair of 60uf 370v and a pair of 45/10uf 440v capacitors so I can try a few different values to see which works best.

If anyone has a lead on a good wire feeder for cheap besides Ebay let me know!

Hi Corey!

Okay, so what you need to do first, is delete the two jumper wires that make this transformer's primary a Y connection. They'll go from Terminal 1 of each coil set, to terminal 1 of the next. Best way to do it, IMO, is just get in there close with a pair of small clippers, and cut the ring terminal right by the stud.

Next, locate Wire 9. Goes from the switch, to terminal B5. Locate and disconnect it. It may be easier to locate and disconnect it from the SWITCH, than to clip it away from the back of the terminal strip (might be buried in a rat's nest of wires). If so, disconnect from the switch, and tape and tie it up good, so it doesn't get tangled in the mechanicals or short somewhere.

Now you'll have three separate coil sets, with two of our input wires already in place!

Next, find wires 20 and 40, they're connected to the back of the terminal strip.
Wire 20 will be connected to terminal 4 of ONE of the coils. We'll refer to this as COIL A.
Wire 20 will be connected to terminal 4 of the middle coil. We'll refer to this as COIL B.

Clip those wires off right at the terminal ring, and pull 'em out where you can work with them later.

Next, remove all the voltage selection jumpers.

Now, on each coil set, make a wire jumper, and connect terminal 1 to terminal 6.

Red 10awg wire from A2 to C5
Black 10AWG wire from A5 to C2

Blue wire from A5 to one capacitor
Blue wire from that capacitor to B2.

Blue wire from C5 to the other capacitor
Blue wire from that capacitor to B5.

Install 15k 5w wirewound resistor across terminals of each capacitor.

Capacitor size will be somewhere in the 130uf range, try to stay above 430v if you can...

Connect Wire 20 (fan motor) to A2
Connect Wire 40 (fan motor) to A5

Tighten all terminals carefully (they're brass!)

On the terminal panel, you'll find three power input terminals... wire 5 corresponds to your incoming line BLACK wire (hot) and wire 7 corresponds to RED (HOT). No neutral (white) is required here, just a green ground connector to your single-phase 240v plug. Connect to a 50A outlet, flip the switch on the front, wait for smoke, then apply hideous laughter while striking an arc.

Diagram - CP-252TS Haas-Kamp single-phase

Okay, let's try this...

By the way... as long as Mr. Kamp is still alive, everyone calls ME Dave.
In the meantime, I take every opportunity to have lunch with my Dad, 'cause someday I'll be Mr. Kamp...

Thanks for the info Dave ;-)! Ill be out of town for the next few weeks so I wont have a chance to tackle the conversion until I get back. Until then ill be studying the diagrams and reading, reading, reading.

So I finally cleared enough time to work on the welder. Using my forklift to move it to my work table I didn't secure the welder good enough to the forks and it tipped off the table onto the concrete floor. luckily no one or thing was damaged besides the welder which actually fared pretty well, only bent the back corner and fan shroud which took about 5 minutes to fix. I learned a darn good lesson about quick rigging on the forklift! I had no access to three phase so I couldn't test to make sure the welder was still working. Instead I went straight top the conversion.

The conversion went really smooth and after triple checking all the connections with Daves diagram I fired the machine up. The fan came on right away and after jumpering the remote contactor (I'm testing it with my 8VS wire feeder) I had voltage at the outputs which I confirmed the machines meter with my hand held digital meter.

I first tried welding at 17v but couldn't get more than a few sparks and the amp meter only read 50a. I cranked it up to 30v but the same problem, only 50A. The voltage doesn't change while attempting to weld. No matter what I set it to I can't get over 50A of output, which of coarse is not enough to run .035" solid wire.

Attached is a picture of how I wired the capacitors in parallel (I think). I am currently running 115uf of capacitors instead of 130, since I didn't order enough. The round capacitors are 60uf 330v and the oval ones are 45/15uf 440v. I checked voltage at a few leads and have 255 volts coming in, and 140v at the capacitors. Ignore the small #10 wires, I ran out of #8 so just used the #10 temporarily. Once I get it running all the connections will be cleaned up and properly secured.

Any ideas on what the problem could be or suggestions on what to try? I would think 115uf would get me in the ballpark.

I went thru this afternoon and checked the wiring again. I had everything correct. I tried the welder with my ready welder with flux core and it would put out over 200 amps set at 30v. Running DCEN or DCEP would result in large craters and blowing slag balls all over the place no matter the voltage or wire speed. I hooked up the 8VS again and was able to get 150amps out of the machine but the welds had no penetration and responded the same in DCEP and DCEN.

Additionally the max OCV is 30V versus the 44v as stated on the label.

Attached is a picture of the welds. The good looking welds at the edges of the picture were done on my engine drive using the same 8vs feeder.

Kinda sounds like it's not getting the center phase to wake up... OR... may have a diode in the bridge that's nonfunctional/broken/shorted. May not LOOK bad, but if it got bumped just right, one could be fractured.

Seein's how ever wire is red, I'm having some difficulty determining wether you wired the capacitors up properly. If so, that'd keep the center coil from playing ball... and I've got a gut feeling you'll need more in the capacitance department. Equip yourself with another 50-75uf on each side and see what happens.

Thanks for the response dave. I have two more 65uf's on order.

Are the diodes you are refering to labled D1,D2 & D3?

Yes, and also make sure the thyristors are good, and connected solid... if one of the thyristors is disconnected, that leg won't carry any current.

When I first started doing these conversions, I kept everything simple by NOT considering the effects of phase-distortion on the output, because for welding purposes, it was irrelevant- the center leg's phase angle would wander (based on load) but had no discernable effect on DC output whatsoever. My thought, when first considered, that the 'wander' may confuse the control board that's firing the thyristors a bit. I helped one fellow through a conversion with a LATER version of the CP-series that used thyristors on half the bridge for 'cutoff' (rather than contactor control), and it worked fine. After several guys sent me messages that they'd been successful doing the conversion on other units that used thyristors not only for cutoff, but also variability, I got the impression that it was probably not as big a concern as I'd anticipated.

But there's no reason to expect that just because SOME machines worked fine under that circumstance, that ALL would, so we're amidst a learning-environment here. This machine may teach us a lesson, and unfortunately, I'm 2000 miles from it, so I can't stick my nose and a pair of test probes in it myself. We'll just hafta see what he finds out.

DaveKamp said:

Seein's how ever wire is red, I'm having some difficulty determining wether you wired the capacitors up properly.

Click to expand...

Looks like he used two dual value capacitors in his setup (taller oval capacitors), which really complicates things. I can see the three wire connections on them. I would ditch them in favor of two wire connection types and re-test.

DaveKamp said:

Yes, and also make sure the thyristors are good, and connected solid... if one of the thyristors is disconnected, that leg won't carry any current.

When I first started doing these conversions, I kept everything simple by NOT considering the effects of phase-distortion on the output, because for welding purposes, it was irrelevant- the center leg's phase angle would wander (based on load) but had no discernable effect on DC output whatsoever. My thought, when first considered, that the 'wander' may confuse the control board that's firing the thyristors a bit. I helped one fellow through a conversion with a LATER version of the CP-series that used thyristors on half the bridge for 'cutoff' (rather than contactor control), and it worked fine. After several guys sent me messages that they'd been successful doing the conversion on other units that used thyristors not only for cutoff, but also variability, I got the impression that it was probably not as big a concern as I'd anticipated.

But there's no reason to expect that just because SOME machines worked fine under that circumstance, that ALL would, so we're amidst a learning-environment here. This machine may teach us a lesson, and unfortunately, I'm 2000 miles from it, so I can't stick my nose and a pair of test probes in it myself. We'll just hafta see what he finds out.

Click to expand...

I'll check the thyristors and make sure everything is solid.

I was curious about the load making a difference since the capacitors are size at full load. I'm no engineer so I am probably way off. The pcb is pretty simple so hopefully it wont cause many problems. I hope I can get is all sorted out, I'm planning on making this machine my main Mig welder and selling my MM350p.

No Vegas vacations planned? :-)

Philabuster said:

Looks like he used two dual value capacitors in his setup (taller oval capacitors), which really complicates things. I can see the three wire connections on them. I would ditch them in favor of two wire connection types and re-test.

Click to expand...

I used the duals so I would have some options of changing up the capacitance 10uf in either direction. I've looked it over and everything is definitely wired in parallel with no mistakes. When I get the new capacitors I'll abandon the 10uf half of the duals.

I took about an hour today to check the diodes (all 4 checked out good according to my meter) and look over the machine. the thyristors (SCR's) look good but I couldn't figure out a way to test them without applying voltage to them and even then they say they really need to be tested under load. I went thru every connection and found no problems.

The PCB is super simple and consists of 13 resistors, 9 diodes and a capacitor. There are no chips at all. The welder is very simple so hopefully the added capacitors will do the trick.

I checked voltages again and I'm getting 250v+/- at the two outside phases but only getting 140v at the center phase that is fed by the capacitors. Are the capacitors fooling the meter or is there a problem with the capacitors?

As far as wire size, is #10 good enough to feed the center section? By my calculation those wires should be seeing 15A which the #10 is more than capable of handling. I cannot find any female crimp on terminals for #8 wire so using #10 would work the best for me.

The voltage you read across the center coil, is a function of phase-shift... a portion of that being capacitance, the other, being inductance. The former, you control, the latter, changes with load. The voltage you read, is a moving target. Once you place a load on the transformer, that voltage will increase, but at the same time, the phase angle at which it's being 'bent', is changing too... because the transformer core's action on the left and right sides, is changing what happens in the CENTER.

Okay, here's one way to consider it:

In an ordinary single-phase transformer, you have a pair of coils (primary and secondary) and a core. The coil's windings have resistance, inductance, and capacitance. Assume the resistance and capacitance are negligable, because at these frequencies, they are.

The inductance, if there were NO core (aka. an air-core) would be very little. Because there IS a core, the core's density and permeability determine that coil's inductance, and therefore, how it responds within a frequency range.

A power transformer intended for 60hz, needs to have core and coil properties that are most efficient at 60hz, and present the lowest losses (minimal eddy-currents within). So in a single-phase, it's all built around 60 cycle alteration.

If you dial it to 50hz, you'll need more mass. Go to 400hz, you need much LESS (this is why 400hz is popular in mobile applications, like aircraft).

Now... in a THREE PHASE transformer, you have the A and C coil sides, with B in the middle. One could use three SINGLE_PHASE transformers, and just wire them in wye or delta, and be done with it, but since the phases are running in 120 degree intervals, rather than 180-degree opposites, it is possible to connect the three cores TOGETHER, and SHARE a certain amount of the magnetic alternation, so that the end result is a smaller, lighter core, and if designed well, even greater efficiency in terms of core loss.

The catch being... what happens between A and C, must also include some action in B.

It's like having a three cylinder engine, using common intake and exhaust. If you kill one cylinder, the tuning of the other two cylinders falls off... because the intake and exhaust pulses are no longer 'helping'.

In a single-phase transformer, the magnetic alternations go up and down. (read 'Right Hand Rule').

In a three-phase transformer, the magnetic alternations go up and down in each core, but must go between A->B, B->C, C->B, B->A.... in a figure eight. That means, when A is pushing south, the outflow goes down, then right, then up through B (so B is opposite A), and then out the top of B, into the top of C, then down... then left, then up B.

So what we're doing, is making this transformer CIRCULATE. Now, it naturally WANTS to, but when you just drive A and C (inverted), B has no real reason to want to play. It's like two girls swinging a pair of jumpropes and Charlie Brown stands there watching. If we push Charlie in (like, powering B directly from A or C), he'll get clocked in the head by one of the jumpropes.

In this conversion, the REASON it's happening, is because we're feeding B with capacitors, and as a result of the INDUCTANCE of B, and the Capacitance we've added, DELAYS pushing just long enough so that SNOOPY jumps in BETWEEN the rope swings, and then, all he has to do, is jump when they're both DOWN... and now, we're skipping Double-Dutch.

Ah, I digress...

Okay, so yeah, the thyristor board, having no 'brains' is a good thing. All it's doing is firing the SCR when it gets to a certain point in the rise... like a lamp dimmer.

Let's try next step- increase capacitance.... go up with both sides, work your way up with whatever you have (don't hafta be 'pretty' with it, just hook up and gun it), and see what happens. When you hit the 'sweet' spot, it'll wake up and burn metal. If you get to oh... 220uf or so, and don't see a change, then it's time to drop back and punt.

I suspect we just haven't found where this transformer wants to come out and play.

Thank you Dave for the explanation. The Snoopy and Charlie Brown analogies really helped me understand :-)

I'll add more caps and see what that gets me.

I installed the 65's for a total of 170uf on each leg. Looking over the wiring I realized I forgot to install the second leg from the inductor to the bridge when I was testing the diodes. I then connected it and fired it up and had a humming and only 20 volts. I looked at it again and realized I connected the leg on the wrong part of the bridge and had directly connected legs 2 and 3 :-0. Luckily there was no smoke and it just made the wires and transformer coils warm to the touch. Its been a long week so I guess my head wasn't into the wiring. Probably not the best idea to be working on 250v equipment with your head in a fog.

After slapping myself, I then went over the diagram and got everything connected correctly to the bridge. Fired it up and had a max of 30v. I could get it to weld at 200a and it seems to weld a bit better but still far from good. It makes a decent bead around 60a, 18v using slow wire feed on the ready welder. I should have two more caps here by mid week to get me up to 215uf.

I received the cap this afternoon and installed them for a total of 215uf per leg. Still no dice. The weld still hasn't changed much and it only hits about 32v max.

Any ideas where to look next?

Something's not right.

Okay, find your connections to either A or C, and reverse them, and try again. Perhaps they have the phasing marks reversed in the diagram.

Which connections are A & C? Is it where L1 and L3 would connect in 3 phase?