Miller CP-250TS converted to single-phase - Page 7
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  1. #121
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    Bennettdan,
    Why is cast iron better core material? Never seen any inductor
    with a cast core. Is it sort of a way to mimic laminations?
    Tvan56

  2. #122
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    I think Dan selected CI rod for the same reason I used an old sash weight- it had lots of iron, and was readily available. From an efficiency standard, a laminated core would probably be a little bit better, but finding a core that a guy can D-I-Y it in his own garage kinda precludes finding some silicon-steel laminations to make his own. Snagging an output inductor from a scrapped-out welder is a shoe-in answer for the CP-250TS, but if a guy has one with the inductor in it (and he's me), he'd probably not wanna rip it out, as he'd be using THAT welder, too.

    Now... one thing I HAVE considered... is that there's a fried-out 3-phase 50kva transformer sitting in my driveway, and if I were to put it in the bandsaw, I could cut that bugger into several really nice laminated stacks. Unfortunately, I'd hafta make sure that the laminations were all properly fastened together, but I could probably solve that prior to cutting, by applying a nice bead across carefully suspected spots in the laminations... and when done, there'd probably be enough space for me to wrap about 30 turns of stout copper on that chunk.

    Would'a been cool, though, if that sash weight did the trick completely... there'd be guys just goin' CRAZY, replacing the aging windows in their house for high-efficiency windows... and saving all the old sash weights!

  3. #123
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    That is exactly what I have been thinking. I have a fried spot welding
    xmfr. of around 100kva. May even have big enough copper in it to
    wind an inductor. I do have a friend who make racks for the plating
    industry and he has the flat copper bar and the benders to duplicate
    that CV300 inductor shown earlier. Just need to get busy and do it.

  4. #124
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    1_6_13-002.jpg1_6_13-003.jpg1_6_13-005.jpg1_6_13-007.jpg
    Quote Originally Posted by tjb836 View Post
    Dave,I have been following your threads on 3 phase welders for a while .I even tried it on a Hobart RC300 for a friend. It works as if it were hook to 3 phase. Now I have come across a new challange and need some help.
    The welder in question is a Hobart RC256. The primary has only 2 coils instead of the normal three. If I have done it correctly, the attached photo should show this. My first idea is to connect one leg to 102 and the other to 101 and103. The transformer seems to be 2 separate units. I am open to any ideas you or anyone else may have.
    PS: the stats
    input
    voltage 208/230/460
    output
    24v 200 amps
    is this the machine you converted if so i would like to talk to you

    archie =) =) =)

  5. #125
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    Quote Originally Posted by DaveKamp View Post
    By the way... on mine... ANY of mine... I didn't hear any buzz... all I heard was the cooling fans roaring. In the 250TS, I'm considering putting some ballast resistance, or perhaps a triac-based dimmer in series, to try and slow the fan down a bit... it's a beast, and I"m sure I'll never work this thing hard enough to need that much airflow... dialing it back just 10% SHOULD cut the noise in half, or more.
    dave I had a linde welder that I thought about streightening the fan blades some for the same reason.
    archie =) =) =)

  6. #126
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    I know this thread is a few years old since any updates, but how has the quest for solving the inductor come for those who have done the conversion?

    I have a converted CP250ts, and it definitely wants to run in the higher ranges. I was hoping to salvage an output inductor out of an old non functioning (mechanically) miller two fifty twin (250A machine), but it's spent too much time in poor conditions to be useful.

    I have tried a coil of aprox. 50' of 1/0 welding lead around a 2" steel bar with moderate improvement, but it gets quite warm, and I'd prefer not to have to lug this around in addition to the machine.

    I'm considering selling the machine, back in its original 3 phase configuration to recoup my $ and working on my CP300 instead, if there isn't an economical way of getting this to settle down in the short circuit mode.

  7. #127
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    Awesome work

  8. #128
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    I got a Miller CP 250 unexpectedly at auction. Placed a bid with no idea of getting it. Might be welder number 10. I should quit bringing them home.
    I think I will start the process of making it single phase. The bugs should be worked out by now.

  9. #129
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    I have a 1975 Miller Cp-300. I want to convert to single phase. Looking for help

  10. #130
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  11. #131
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    Quote Originally Posted by YoungDen View Post
    I got a Miller CP 250 unexpectedly at auction. Placed a bid with no idea of getting it. Might be welder number 10. I should quit bringing them home...
    It IS a sickness. I have 6 that have come home with me...

    Successfully converted 3 so far. 1 works, but doesn't quite work right, and one is currently a work in progress. 1 doesn't work at all, and I don't know if it was working to begin with. I'm batting 500!!!

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    I don't see where you get an I of 18.6 / 3 on the CP-250 mod. Congratulations on your work. I try to tell people all the time that these older welders are very reliable. The newer inverter types are great when they work. Out of warranty work can be expensive.

  13. #133
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    So it's been a year or so, what the heck. I'm trying to help a buddy convert a Miller SRH-404 from 3 ph to single. Is there anyone who can help on this line? Thanks

  14. #134
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    Try here:Miller SRH-333 to 240v single-phase This looks very similar.
    It may help to start another thread to get more attention.

  15. #135
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    Hi, I know this is an old thread and there is another thread on the CP-252TS, but I was looking for a little help understanding the CP-250TS before I start on a later model CP-250TS. I have a converted CP-300 that works great, but when I compare the volt-amp curves for the CP-300 and CP-250TS, the CP-300 seems like it would have less inductance just based on the flat slope of the volt-amp curve. Do you think the CP-300 just shows the low inductance setting (mine has two settings). I have an output circuit from a POWCON 300SS (output inductor-capacitor filter followed by another inductor in series) I will try on the CP-250TS once I get it converted.

  16. #136
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    John, the impression I get (both from experience, and discussing it with an engineer that worked on the development) is that the CP-250TS's transformer design was superceded by the CP-200/300 as a result of short-arc welding process being the upcoming mode of choice... I believe the CP200/300 core design doesn't need as much external inductance, because the CP200/300 core naturally exhibits the reactance character that the TS could not attain without an external feature.

    One thing that's important to remember: The CP200/300 are TAPPED transformer designs. When you have it cranked up to higher voltage, there's more secondary windings, and as a result, more inductance. At lower voltage, you have lower inductance, but higher current available to provide muscle if you're running enough wire speed.

  17. #137
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    Dave, thank you for the message! I took some inductance measurements to get an idea of what's going on before saturation. The CP-300 measures 94uH (low inductance tap) and 194uH (high inductance tap). The CP-250TS measures 10uH at Tap 0, 100uH at Tap 8, and 194uH at Tap 14. I don't plan on thinking anymore about the effects of the inductors placed before vs after the rectifiers, other than I would imagine it isn't too different. The two inductors from the POWCON measure 49uH (part of output filter so I don't expect it to saturate before the POWCON's 375a max current) and 453uH (this is the output stabilizer and the coupling coil for the arc starter circuit and probably saturates well below 375 amp). I am thinking of using both, with a 15000uF capacitor in parallel with the output rectifier.


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