Miller CP-250TS converted to single-phase - Page 2
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  1. #21
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    Default So what I've done here...

    So in reviewing the photos, what I've done here is:

    Set all jumpers for the 230v position. There's an auxiliary transformer in here to power the controls, so that makes FOUR sets of jumpers.

    Removed the fan housing (disconnect two fan leads, and remove two screws down at the bottom), lifted it out of the way.

    Two bolts hold the wiring terminal strip - remove those, and then remove the jumpers providing power to the center coil, attach two blue wires there. Install a new power jumper from the far coil (on the contactor side) to the far edge of the opposite coil... now the two end coils are 180 degrees out-of-phase. I used red wire for the jumper, as it will be one leg of the 240v single phase setup... the other is black, which is the natural color the manufacturer used.

    I've carried black and red leads around to the capacitor array, and wired them to one side of each pair of capacitors. The other side has one blue wire (one for the red side, one for black) going to the center coil. No polarity issues on the blue wires... leading or trailing by 90 STILL results in a figure-8 flux sequence. I've put jumpers between the capacitor segments... SOME of these may get disconnected if observation rules that I can change final capacitance if necessary.

  2. #22
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    Default Progress update...

    Okay, it's been stormy, hot, and muggy here for the last week... entirely NOT conducive to being in the workshop, but I have made a little progress...

    Unfortunately, the cost of this conversion took a huge leap...

    Typically, I've been using off-the-shelf 'range cords' for my conversions... when you set a big welder up in a stationary application, you only need about 6'. This time, I wanted to be able to roll the CP-250TS around a bit. Also, my shops are fitted with 3-pin 250v/50A plugs that look like common 120v outlets on steroids. They've always worked well, because in general practice, I never set up my machines to require a neutral.

    But... the local stores have discontinued this plug type... now they ALL hafta have a danger-wire (white)... and they've discontinued carrying 8/2 + 10/1 in SO cable, now you get 8-4 (huge) and the 14-50P plugs that don't have enough internal space to keep one terminal's screw from digging into the adjacent conductor's insulation. (Brilliant!).

    Oh, and of course, to make it work, I hafta install the stupid 14-50R socket to the wall... all this stuff... rather than costing $14 for an 8' range-plug... added up to about $150.

    If I wasn't planning on rolling this around, I'd go with a different range-plug and be done with it... but getting longer wire didn't leave many options... it'll work for now, mebbie I'll find a better solution and yank this 8/4 and use it for 3-phase (it is 600v) later.

    But for now, we'll get it wired and fired, and hope for no smoke. Looks like we get a couple'a cooler, drier nights, so stay tuned!

  3. #23
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    Very nice Dave! Im a huge fan of Miller machines. You are a smart guy with the electrons!

  4. #24
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    Thumbs up Thanks for the support, Dave...

    Sorry I haven't posted any progress here... just got back from a 2-week company assignment, and still trying to catch up on the honey-doo's, but hopefully will have this one's power cord wired in, and the wire-feeder installed, wired up, and ready for a metal-burning test over the weekend. I've got some welding projects to do, so I'm well-motivated.

  5. #25
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    Dave,

    A 3 phase DC welder would give a more stable, smoother arc than a 1 phase welder?

    What you are doing is to lag the one leg of the input with the capacitors to stick a bump in the middle of the other two bumps?

    Assuming we are looking at the DC output wave form on an oscilloscope.

    Paul

  6. #26
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    "Typically, I've been using off-the-shelf 'range cords' for my conversions... when you set a big welder up in a stationary application, you only need about 6'. This time, I wanted to be able to roll the CP-250TS around a bit. Also, my shops are fitted with 3-pin 250v/50A plugs that look like common 120v outlets on steroids. They've always worked well, because in general practice, I never set up my machines to require a neutral.

    "But... the local stores have discontinued this plug type..."

    Three-prong "range cords" (really, these are heating appliance cords, and are applicable to ranges, cooktops, ovens and clothes dryers) are still legal in most jurisdictions for "old work" or "replacement in-kind" applications.

    The more-or-less standard three-prong plug, available at almost all ACE Hardware stores, comes with four prongs, a molded plug and cap, in a bag with instructions.

    I believe the actual parts are made by Cooper Industries.

    Anyway ...

    When assembled using only the supplied straight prongs, the device is rated 50 amps, although it is really capable of 60 amps.

    When assembled using the two supplied straight prongs and the one supplied "L-shaped" prong, the device is rated 30 amps, although it is really capable of 50 or 60 amps.

    Three-prong receptacles are still available in a variety of case styles, from the molded case, surface-mounted type to the bracket-mounted type which is most suitable for installation in a 4 x 4 "deep" box.

    (I use the surface-mounted type in my residence, and the 4 x 4 "deep" box-mounted type in my shop, which is in a separate structure from my residence).

    As a residential "heating appliance" will almost never be installed in the same structure, or the same room as a welder, I suppose you can accept the almost infinitesimally small risk of a mix-up, and install a 50 amp receptacle and a matching plug and cord cordset which uses, say, #6 stranded wire in a SOOW or SJOOW cord style.

    (SJOOW is rated for 300 volts, so it is the most economical choice for 240 or 120/240 volt applications. SOOW is rated for 600 volts, so it is the appropriate choice for 480 or 550/575/600 volt applications).

    I would spray-paint the devices red, or another distinguishing color, and affix a placard which designates that receptacle as "suitable only for Haas-Kamp-converted welders" ;-) .

  7. #27
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    Here ...

    Cooper Wiring S80-SP 3 Wire Angle Power Plug Black #6857684 at HardwareAndTools.com

    ... is a Cooper 120/240 volt 30/50 amp (male) plug which could be re-purposed as a 240 volt 30/40/50/60 amp (male) plug for a single-phase welder purpose. Matching (female) receptacles are available from others.

    Here ...

    Cooper Wiring S42-SP 3 Wire Grounded Power Plug Black #6409478 at HardwareAndTools.com

    ... is a Cooper 240 volt 30/50 amp (male) plug which could be re-purposed as a 240 volt 30/40/50/60 amp (male) plug for a single-phase welder purpose. Matching (female) receptacles are available from others.

    I have found that most ACE Hardware stores, and also all OSH Stores (perhaps in California, only) stock these.

  8. #28
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    For you purists out there, here …

    Cooper Wiring S21-SP 4 Wire Grounded Power Plug Black #6410096 at HardwareAndTools.com

    … is a 4-pronged 120/240 volt 30/50 amp U-grounding plug, and here …

    Cooper Wiring S42-SP 3 Wire Grounded Power Plug Black #6409478 at HardwareAndTools.com

    … is a 3-pronged 240 volt 30/50 amp U-grounding plug.

    For the welder application, you would use three conductors, only: L1, L2 and protective ground (never neutral).

  9. #29
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    Default A "bump"...

    Hi Paul-

    "bump"... hmmm... Well...

    What's happening, is that the 120 degree span between legs now becomes 180 degrees, and the center coil is phase shifted 90 degrees, so you have something not unlike a 'two phase' system of long ago. What we're looking for here, isn't a purist result, but rather, a method that will lay down decent welds as would be expected from a machine of industrial caliber. While a little bit of performance loss is expected, it shouldn't be so high that the user needs to seriously reconsider before making a weld.

    Of course, running the welder on three phase, as originally designed, would yield the best result. We're not doing this to 'beat' that concept. We're doing this so that a guy can buy a used industrial-grade machine, and power it with reasonable performance in his home or farm shop, where only single-phase power is available.

    If you look for conversion info on many of these welders, you'll see that the most common answers are:
    1) Impossible
    2) Possible, but miserable performance
    3) Possible, but cripped above a certain point.

    The conversions noted are usually either just disconnecting the unused leg, or driving all legs in phase, or driving the center leg in reverse phase. Trying to drive the transformer missing one leg, or trying to drive 'em all together, means the magnetic flux is flipping back and forth between ends of the polepieces, but not working as a 'team'... instead, they're actually 'bucking' eachother.


    What Peter and I worked out, does NOT do any of those, but rather, it re-establishes the A-B-C sequence enough so that the MAGNETIC flow through the core mimics that of the original 3-phase connection plan. The result here, is a transformer with 3 acting cores, and the flux pattern is a figure-8.

    When operating at minimal load, that center core isn't carrying much current, but as you load the machine, the capacitors increase phase shift, which at max, is at 90 degrees, so the A-B-C sequence is back in order, so the transformer is back to developing output in the realm of it's original design.

    And it works... matter of fact, it works wonderfully... better than I expected.

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    Thumbs up Progress...

    By the way, I've been doing lots of business travel, so haven't had a chance to put much time in on my projects, but I DID get some progress here today.

    Fired up the CP-250TS this afternoon... all control circuits and fan motor working fine, but had no DC output... and after metering, saw no DC input. Reason is because I selected the wrong wire coming off the main contactor's terminals... was getting no AC power to the input of the main transformer. FOund correct wire, corrected wiring, and now it's showing 31.5 OC volts.

    Now I'm wiring up the wire feed unit.

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    now it's showing 31.5 OC volts.
    Dave, you may want to examine that farther ... both my inverter power source (HTP Invertig 201) and my engine drive (Miller Trailblazer 302) run closer to 80 OC volts, sometimes 90. Enough that when my gloves are sweated through & an electrode is held to tap-start an arc, a strong tingle is often felt.

    As soon as the arc is established, the voltage drops to the "normal" 20-25 volts.

    ----------------
    Barry Milton

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    We're doing this so that a guy can buy a used industrial-grade machine, and power it with reasonable performance in his home or farm shop, where only single-phase power is available
    and cause these old 3ø machines are 10 cents on the dollar compared to single phase in the same year and size class and include wire feeders that put the little machines to shame.

  13. #33
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    Default Ocv...

    Hi Barry!

    Yep, on TIG and STICK applications (Constant Current), it is very normal to see OCV numbers from 50-85V, and then have 'em sag to 25 or so under load- that's what makes it separate from a 'constant voltage' supply.

    The CP-250TS is a Constant Voltage supply, and while that's somewhat of a misnomer, the reality is that the supply is wound and core-saturation calculated so that the amount of variation from open-circuit to full-capacity arc is pretty minimal.

    There IS a certain amount of SAG that has been designed into the CP-series welders, that's so that the wire feed rate vs. arc current self-stabilizes. The wide variation of a Constant Current welding supply is what makes it unsuitable for wirefeed welding.

    But the numbers I'm seeing for OCV are quite proper- the CP-200's operating profile is exactly the same. The SRH-333 conversion (a DC-only stick/tig supply) looks a whole lot more like yours... OCV up in the 80's.

    I'm kinda held-up right now, as the CP-250TS has a twist-lock 3 conductor 115vac power receptacle for the wire feeder, and I don't have one of those plugs... so I'm hunting for opportunities and options here.

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    I'm kinda held-up right now, as the CP-250TS has a twist-lock 3 conductor 115vac power receptacle for the wire feeder, and I don't have one of those plugs... so I'm hunting for opportunities and options here.
    bungy in a drop cord, male end on the feeder, female on the power supply

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    on TIG and STICK applications (Constant Current), it is very normal to see OCV numbers from 50-85V, and then have 'em sag to 25 or so under load- that's what makes it separate from a 'constant voltage' supply.
    I appreciate that easy to understand explanation

    Ran my Trailblazer 302 for 59 hours on a recent construction job - high heat & high humidity, so the gloves were always moist. Did almost all the welding from a fold up step stool (plastic) so never got a shock, even using the left hand to guide the 7018 rod for tap starting.

    Preparing for that job was a different story, since practice pieces were set up in the shop vise & my elbow leaned against the metal welding table for support. Lost count of how many times I got zapped, although none of the shocks were painful. Just distracting when attempting to lay in a perfect, code quality weld

    FWIW, the TB302 runs either constant current for stick & TIG, or constant voltage for MIG. Using the Miller Suitcase 12RC feeder and Lincoln NR-212 flux cored wire, there is nothing sweeter for portable MIG.

    -------------------
    Barry Milton

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    Default Sounds right...

    That sounds right, Barry, but try this once:

    Set your TrailBlazer to CV, and put a voltmeter on the output, see where it goes open, and then measure under MIG arc... I'll bet the OCV isn't as high, and it doesnt' sag as much.

    Peter- I got a chuckle out of your plug-marking reference... think I'll have a buddy engrave that on a piece of plastic, to make a replacement for the receptacle cover... ;-)

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    Default Great thread!

    Dave, been following this build of yours with interest, as has been stated before, the HD 3 phase machines are a much better value than single phase comparable machines. I'm not that great with wiring diagrams, but looking at your rebuild, it seems in the realm of possibility for me to do, taking time to study up and not rush it, of course. Just wondering how this one is coming, it's been a few weeks since you've posted on it, and it sounded like you were getting close. Oh, and one question, if you had your pick of the litter of any 3 phase industrial duty machine to convert, which make/model/year would you choose, and why? Thanks much!
    Last edited by alha; 10-06-2010 at 03:56 AM. Reason: spelling...

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    Thumbs up Hi Al

    Sorry about the lack of updates... company travel has made my home-time somewhat fragmented. My most recent work on it, has been fitting up a wire feeder (leant by Wippinboy Kevin) 'cause my Craigslist 10E feeder has turned out to be a dud... cursory probing with voltmeter suggests that the SCR in the feed motor armature circuit isn't firing. Rather than burn diagnostic time, Kev leant me a nice 10A (identical, but nicer than the one used on my CP-200 conversion project also appearing here on PM). I have the controls working, but haven't had time to make the final power jumpers.

    I DID, however, check the CP-250 TS by borrowing cables from my stick welder and clamping in a 3" segment of channel iron... I triggered the CP's contactor, and dialed it up... got to 300A at 26v (indicated by panel meters), so roughly 0.08 ohms. My Fluke obviously isn't incredibly sensitive down that low, but sounded reasonable to me. Didn't trip the 50A breaker, so she's clearly a winner.

    As for favorites... well, I've been doing Millers, particularly the pre-solid-state-output units. If you search the forum, you'll find that I've already done the CP-200 (mig) and the SRH-333 (stick) supplies... then this one.

    They all have a few things in common- First, they're serious industrial workhorse castoffs that few people are willing to work with (pronounced "inexpensive"), they have a 3-phase power transformer that can be somehow configured for 230v input... and there are wiring diagrams and owner's manuals available for free right off the website.

    There's LOTS of variations of machines out there... Lincoln, Airco, Hobart... all industrial-grade welding supplies, and all have a 3-core 8-shaped transformer. I'm sure that I could convert most welders that have such transformers, but having those diagrams on-tap really makes it easy to perform and document... so if people are gonna ask for my assistance on converting 'em, I'll choose ones where I can look at the same diagram, and know that they've properly identified the machine, the wiring, etc. Anyone who's sharp enough to understand HOW the Haas-Kamp conversion technique works, is sharp enough to figure out how ANY 8-shaped transformer core is wired, and thus, won't be limited to any brand or model... but so far, I've fielded about 30 direct inquiries about conversions, and 22 have actually performed and reported back to me, all with positive results.

    The only comment I have about the ones I've done (and assisted on) so far... is that Y-input machines (like the CP-200 and CP-300) can be a little more tricky to identify the wires. I already did the math to sort it out on the CP-200, and to make 'em work really well, the OUTPUT side has'ta be converted to Y output (to boost output voltage up a smidgen)... so the preference is towards a delta-input machine, but they all work well. The best ingredient is patience.

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    Post Status update: Testing

    Hi Everybody!

    Okay, so I've been slightly swamped with work, but I HAVE managed to get cables made, etc., and set it all up for a test tonight.

    Yep, it welds. Welds smooth, but doesn't weld great... or perhaps I should say, what I'm seeing for meter indications doesn't match what I see in the weld puddle.

    I suspect that what I'm seeing here, is a failure of the current-measuring 'shunt'. First failure result would be an errant current reading, and I suspect this to be the case- I was able to hit 400A well before the manual's V/A curve indicated... and when I did, the bead didn't have penetration indicating anywhere NEAR 400A...

    The second failure, is lack of penetration, which means the arc energy isn't high enough...

    These two things in common suggest to me that the metering shunt is failing... generating high resistance, and preventing current flow, while at the same time causing an excessively high meter reading.

    Another possibility is that I have a bad diode or two.

    Since I had no opportunity to check this machine PRIOR to the conversion, I'll be exercising my brain to sort out just what the problem is.

    I'll investigate this further this week.

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    Hello,
    I have a CP250TS i just traded for and I plan to convert it to single phase. I looked at your electrical print and i dont see where you have your Caps hooked up if you dont mind posting your full print i will convert mine and see if mine has full power output mine was working before i bought it. Thanks


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