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Ok, I hooked the welder up as shown in the last drawing and here are the results: OCV 27 volts The best I could see the amps were approaching 200 with wire speed at max. I am working alone so it is difficult to weld and also watch the meters.
It is still sputtering some but am not sure if it is a wire feed problem or maybe not enough gas as the torch lead looks as if it had been hanging on a hook for a while. It has a bad kink in it. I will probably have to get a replacement.
All in all it looks promising so I will continue on with the project. Any and all feedback will be appreciated. Get a better image of that second diagram. Specifically, the upper left quadrant.
My cursory look at the diagram suggests that since it has two separate cores, there's no need for capacitors. There's no three-phase sequence occuring here. What they did, was just set it up so that it was driving off of all three legs, with just two windings. It's really just pulling from A to B, and B to C.
With the coils wired as shown in #3, it SHOULD be working. Now, the lack of stability makes me suspect that there's a problem with some component somewhere. Either the output controls, or a rectifier, or a power contactor. A clearer look at that diagram will provide good direction towards troubleshooting. Always keep in mind, that when converting a 3-phase welder to single phase, that there's a REASON why the machine ended up in your hands. I just completed a conversion and improved step-by-step writeup of the CP-200, and in my unit, I found that it had been pulled off the production line and put in a storage bin simply because one contact of the welding power contactor had burned. Every time I pulled the trigger, I got a different output voltage.
Dismantled the contactor, and the top half of the contact fell out of the works. Slapped in a surplus contactor from my storage warehouse of evil devices, and it works like dream now! Okay, so I've been contemplating this one more, and I wish that you, me, and it was sitting in the shop, so we could team up on it. This welder uses two separate cores, and they're wired with two primaries together, hooked to the 'B' phase, with the far ends of each hooked to A and C respectively. This corresponds to delta, but with one core (A to C) missing. The outputs are wired just the same. Tied in delta to a three-phase rectifier array.
My gut feeling here It will probably work alright wiring A and C of the primaries together, but it'll probably work the rectifiers over pretty good, as they'll be carrying current in a different sequence, so the cyclic currents will likely be high. If you REALLY wanted to try an synthesize the original working condition, you could try driving one coil directly off the mains, and driving the second coil with some capacitors to phase shift it.
Optimally, you'd do it at a 120-degree interval (360 / 3 = 120), but the limit would be 90 degrees. I'm thinkin' that the end result would be fine at 90, you'd have quadrature going through the rectifiers. Which is essentially what happens in an H-K setup. Off the top of my head, I'm thinking that just installing a pair of caps in series with each lead of one coil would be enough to determine wether improvement is within reach. The mathematics for estimating appropriate capacity will follow the lines of what I did with the CP and SRH's, so get the ballpark, and then give it a try. Yes, I DID take voltage readings, and while it was interesting to look at, I've come to the conclusion that the apparent voltage probably isn't all that indicative of anything, because there are too many variables at play for the reading to be relevant. Current flow IS more relevant, but it's also LOAD dependant.
And loading is a very big (and wild) variable. Just like an RPC, the amount of phase-shift that occurs, and the voltage and current that appears, is very dependant upon the amount of load. The best I've found, Is to get them so that the output look-and-feel is close, then work with it a bit, and 'trim' the capacitor banks until the machine and operator are happy. Your RC is really unique in respect to what I've been doing with the true three-phase machines. And if you've got it working really well, document out all the steps, indicate it on diagrams, and post it! Because you have two separate transformer cores, you won't get the same benefit of the H-K conversion- the 'flywheel' of flux circulating through the shared cores. You may find that you'll get better performance with a lesser value at low power, but need more capacity at higher levels.
Reason why I suspect this, is because Peter and I based the calculations on the common-core's design FLA-per-winding, and then I experimented backwards to find the 'sweet spot'. Transformer cores and windings aren't ideal or pure, and in the case of a welding transformer, they've got some design characteristics that wouldn't be employed in a power or signal transformer. When running the transformer at the low end of the power range, the amount of magnetic intensity developed and passed through the core won't be an even proportion to input. And the amount of capacity will obviously skew what's really happening.
It's permeability, saturation, reactance, and stuff like that. I have finally gotten around to finding and posting a better copy of the diagram.
Dave, if you see this and have any ideas to make the conversion better I would like to hear them. In using the welder more, I have found most of the problems I was encountering had to do with the liner and rusty wire.
Having remedied these problems it runs fairly smooth. I am thinking of trying my original idea of 180 deg. Out of phase again to see how it works, now that I found the problem may have been the wire and liner. I have finally gotten around to finding and posting a better copy of the diagram.
Dave, if you see this and have any ideas to make the conversion better I would like to hear them. In using the welder more, I have found most of the problems I was encountering had to do with the liner and rusty wire. Having remedied these problems it runs fairly smooth.
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I am thinking of trying my original idea of 180 deg. Out of phase again to see how it works, now that I found the problem may have been the wire and liner. Yeah, having wire/liner and other ancillary problems really screws up the empirical results. Just so you know. TA and TB appear to have extra windings X3A-X4A and X3B-X4B are 'buck-boost' windings.
What happens, is that when the hi-lo switch is thrown in one direction, a certain amount of current from the windings labelled '115vac' are fed to the variable transformer (inverted V shape), then routed to the smaller winding of the 'buck boost' coils. When the switch is thrown to LOW, the polarity 'bucks' the output voltage down. When it's thrown to HI, it 'boosts' the voltage up. I've been working on a conversion for some Airco CP-series machines that use a similar technique.
But somewhat more complex. The 'catch' of the buck-boost concept, is that there's a phase-relationship that MUST coincide with the buck-boost in order for it to exhibit consistent performance along that variable transformer's range. The variable transformer is PROBABLY a variac, and it may be arranged so that it is, by nature, a 120-degree-interval device. If so, it's somewhat aloof in a 180 degree circuit, but that doesn't mean it won't work. The results of your experimentation should identify how critical that sixty degrees is. I think the biggest giveaway of a problem, would be detected by an infrared thermometer pointed at various components, and plotting out all the readings over a range of output loads.
Substantial temperature rises on one branch of the variac MAY clue us in to what's happening.