CP-200 Terminal block wiring and single phase conversion
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  1. #1
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    Default CP-200 Terminal block wiring and single phase conversion

    Howdy,

    I purchased a CP-200 a couple days ago with a nice looking old hobart feeder for a reasonable price. The gentleman i bought it from gave me the impression he didnt know much about electricity and had bought the unit cheap with the intention of running it on single phase with no conversion or adaptation. When i arrived to pickup the unit i inquired more about this and he said he bought it used from a guy who had tried to convert it but it never worked and he sold it. I asked about the state of the wiring and was assured he hadnt opened the unit so everything should be factory inside. He had no 3 phase power to test and we arrived on a price taking into consideration the fact that i couldnt test it.

    Mistake#1, not pulling side panels and investigating right there

    Mistake #2 not noticing screws from said side panel partially missing


    Opened her up today and found this



    Lots of new wires added to the front terminal jumpers and lots of cut wires on the back in addition to the terminal numbering called out in the haas-kamp conversion procedure.

    So, best i can tell someone did the conversion (most likely improperly or incompletely) and did all this to revert back to original wiring. The first issue i spotted is a broken solid wire off the top transformer, could have been the issue this whole time.

    I'm unsure where to start, do i get a listing of what the factory wiring should be and double check whats there now? Do i pull everything off the terminal block and start fresh?

    I have wire and 2 55/5mfd caps will be here buy the end of the week. Wasnt expecting such a mess when i went to go clean things out to start today.

    Thanks for any help. Thanks to Dave for writing this quide and helping us all get through it!

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    Once you thoroughly understand the theory of the conversion, you'll be able to master the wiring.

    And there are various flavors of the CP200, the Kamp Haas candidate is the 230/460 version (right?)

    Mistake #3 is not being aware of which version is the candidate you require.

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    According to the data plate on the machine its a 230/460 unit, which i understand to be the correct one. This was verified prior to purchase. Serial number puts it about 1980 which is also similar to the one used to do the original conversion.

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    If it's 230-460, then it'll be identical to the 'step-by-step' doc. Broken wires on the back of the terminal is not uncommon- that copper wire is rather hard, and they CAN crack, particularly if the terminal strip is handled a little rough. I'm certain that I mentioned it in some of the threads- the very first unit I attempted the conversion on, came to be on-the-cheap from a guy who'd fought it for years, and the problem I found, was a cracked wire.

    Correct the wiring, get it hooked up, and burn some metal!

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    Got her all wired up and going but wasnt burning right, low voltage. Less than half of the reading on the chart.

    checking voltage around the transformer wiring it looks like the output from the caps is only 140v.... so is that a cap problem or? others are 243 or so. This was confirmed metering across the input leads and output leads of the caps
    Last edited by Jared; 09-12-2015 at 11:34 PM.

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    So increasing the caps seems to increase voltage, at 145uf im seeing 173 volts at coil 2. i didnt have enough caps to go any higher then that. should i be adding caps to get 240 volts across coil 2? why is my cap value so far off? If the values i tested are linear that suggests ill need roughly 200uf of caps to get 240v

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    Quote Originally Posted by Jared View Post
    Got her all wired up and going but wasnt burning right, low voltage. Less than half of the reading on the chart.

    checking voltage around the transformer wiring it looks like the output from the caps is only 140v.... so is that a cap problem or? others are 243 or so. This was confirmed metering across the input leads and output leads of the caps
    The voltage readings you get on the output side of the capacitors will be irrelevant for troubleshooting, because it is phase-shifted and load-dependant.

    Most of the time when this happens, the issue is simple and elsewhere. These machines come out of industrial service for one of a few reasons- either they went out of business, took that machine out of service in leiu of a new robot, or they developed problems and opted to buy a new system rather than fix it.

    This is why some guys have no problem making conversions work, and others are challenged a bit. My first one challenged me, because it was in the third category.

    After doing many conversions of not only the CP200, but all the others, I found a few points of problems:

    1) Broken wires on the BACK of the terminal strip. The wires coming from the transformer primary are solid copper, and make an abrupt bend right before reaching the terminal strip. They're brittle at that bend, and thus crack, and the crack is often very hard to see and find. I found mine by accident, and in process of repairing, had another crack and break same way.

    2) Dirty/worn face on the secondary variable side. Notice that the whole side of the transformer cores' secondaries is a large sweep surface, and the hand-crank controls leadscrews which raise and lower three sets of brushes. These are the variable contact points for controlling primary output voltage. In many cases, the CP-200 and CP-300 were used in production where once set, the brushes would rarely, if ever, change. in a robot, for instance, the machine would be set up initially, and NEVER change, because it'd be spitting thousand-pound spools of the same wire for years-on-end... there was never any reason to change. During this timeframe, the REST of the variable stack would NEVER see the brushes come across, so the surface would corrode a bit, and become contaminated. If someone attempted to adjust the brushes, they'd get crud between the surfaces, and then not carry current. Hence, when I do these, I crank the brushes all the way down, then scrub the top half to shiny clean, then crank the brushes to the top, and scrub the bottom, then clean the brushes up good... after which, the machine is MUCH happier.

    3) Poor contact in busbars, internal high-current connections, cable connections, or cables. Typically when this happens, the voltage under a crowbar test (placing a piece of scrap steel between the output terminals and triggering the machine's contactor) seems high, but current is low. That indicates that resistance from the transformer's output is too high... and limiting current. During welding, the resistance across arc gap is about 0.1 ohm... that yields about 160A at 18 volts. Dial it up to 21v, you'll be passing 210A across the same arc, and you'll be generating substantially higher heat. IF there's ANYTHING in that secondary path that has ANY measureable resistance, it will limit arc current, and prevent your arc from having heat. To find this sort of problem, once you've established that you have output (that the crowbar test indicates high current), the next step is to run the machine, either with a gun, and attempting to weld for a few minutes, or using the crowbar test for about 10 seconds, then disconnecting power, and checking all the cables, connections, busbars, and contactors for heat. ANY connection that is getting warm must be disassembled, scrubbed clean, and reinstalled.

    NOTE: Don't discount the welding cables- they're fine-stranded wire, which can draw in moisture via capillary action, many feet UP the wire, and cause the pretty red copper inside to become fuzzy green powder that doesn't carry electricity. Substitute for KNOWN GOOD CABLES for testing.


    4)Failing contactor. The contactor has three sets of terminals. Most of the originals I've had apart, looked to have (had) silver plated contact surfaces... very good stuff, but Over time, the terminals will loose a little bit of plating. If it were a normal manual-shop supply, the plating would probably last several generations of lifetimes, but in a welding robot, they'd see literally tens-of-millions of cycles, and those contacts which would likely never need replacement, eventually burned through. Although they look good and clean, they may not be making good contact. See note above about resistance- even the SLIGHTEST, will be a problem. The giveaway, is local heat. An IR thermometer will tell you nicely WHILE the machine is in operation... just how much the temperature is rising on a contact, so if you have one, light it up.

    *Later models of the CP series were BUILT with no contactor- instead, three of the six output rectifiers were replaced with SCRs, and a gating circuit switched the SCRs on anytime the gun trigger was pulled. While the contactor was actually very reliable considering the duty to which it was applied, the solid-state switching totally eliminated the need for contacts, so it took what was already very stout, to making it obsolete. I have worked on CPs that were originally built with contactors, and later on, fitted with SCRs and a control board. I suspect that there was some sort of either a 'retrofit kit' applied to these, or they may have been built at a point where the manufacturer was amidst a design change, where many machine frames were built with brackets for the contactor, but the circuit board was being installed at-factory-build-time anyway.

    I've never found a CP that actually had bad windings. I'm sure there's been a few that burned up from some problem, but catastrophic internal failures on things like this are usually so obvious that one doesn't need binoculars from football-field distances to recognize it. If yours was fairly clean and normal-looking, I'm certain this one's issue is something simple.

    Hopefully that helps. Patience and methodical testing should get this one going.
    DK :-)

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    Thanks so much for the help Dave, all of us converts are surely lucky to have your help along the way.


    I was mostly waiting to figure out if the voltage at the primary side of the coil was an issue or if i should look elsewhere. You answered that and sure enough the contactor contacts were hammered and getting quite hot.

    So off to replace the contacts or the whole unit. Thanks for the help again!

    Jared

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    The contacts were replaced and the issue continues. After several minutes of welding the middle transformer coil was only slightly above room temp while the top and bottom were in the 140f range. this was with the voltage at max. I was only seeing 21v at the gun. So im thinking the issue is a broken transformer wire and that middle coil isnt getting juice. Going to troubleshoot that this weekend. I wish those damn wires weren't so fragile.

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    That certainly means you're not getting power flow through the coil... and yes, a cracked wire would be my suspicion. I'd think that the wire was somewhat hard to begin with, and hardened more from the coil-winding operation... I don't THINK they would have selected materials and process to yield such hard conductors... or it may be that vibration in-use was a contributor, but the long and short of it, is that they crack.

    What I would probably do... is unhook the connections to all taps on the coil, then take an ohmmeter and measure from tap to tap, and determine WHICH tap is indicating the 'most unique' value. Some will be very low resistance, and others somewhat higher, but you shouldn't have any 'high resistance' connections, other than the bridge between one set of coils and the next.

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    I have checked resistance on all 6 coils and the middle 2 coils reads differently than the rest. The odd thing is the top and bottom two coils show continuity between all 4 wires. This is different than the middle coil. This resistance changes depending on if its one end of the coil to the other end (low resistance) or between coils (higher resistance)

    Should the 6 coils all be independent?

    Thanks guys. Gonna get this figured out this winter so i can move on to the sharp mill.

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    Y'know... the previous guy may not have gotten all the cross-connect jumpers removed. Look on the back of that terminal strip, and see if there's some that he didn't remove.

    FWIW, when I did the first one, I opted to do it in a 'fully reversable' way... by removing nuts and taking off jumpers from the back-side. I found that doing so, put me at risk of breaking the transformer leads. The next time, I got smarter, and used end-cutters and snipped the jumpers out, so I didn't have to pull the terminal strip out and risk breaking wires or terminals off. The side-effect, is that those jumpers would need to be replaced if I ever wanted to 'put it back to 3-phase'...

    But... if I were to do that, I'd make my life a whole lot easier, and put the darned jumpers on the FRONT side, where they're visible. ;-) (the guys that whined about it being 'not reversible' ... sheesh...

    IF the coils are separated, then you'd see continuity at just two points... one end of each. If not, there's certainly something not connected right.


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