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Haas-Kamp conversion for Miller CP-300, and CP-302 200-230-460

DaveKamp

Titanium
Joined
Oct 3, 2004
Location
LeClaire, Ia
Hi All-

Recently, I got some inquiries about conversion of the Miller CP-series that are set up for 200/230/460v 3 phase.

If you've read the threads on my conversions of the 230/460v versions of the CP-200, you'll note that there's wiring on the primary side (phasing and capacitors) as well as the secondary (changing it from delta output to wye). This is because the CP-series is Y input, and the wiring on the primary side nullifies the Y... it drives the coils... which are expecting 277v... at 240v. By switching the delta output to Y, it brings up the secondary side the exact same ratio as lost at the input.

Later models... particularly CP-300 and CP-302 frequently appear with taps for 200v, as well as 230/460.

Where a 200v Y input exists, a different choice of input tapping makes it a perfect candidate, and at same time, no secondary modification is required.

It has already been tested with Ari's CP-300, and will be tested on Vern's CP-302 in the near future.

Stand by for details!
 
Okay, so Ari hasn't posted anything yet, but here's the preface:

There are versions of the CP-200 and CP-300 that have 200-230/460v operation.

On the ORIGINAL conversion (230/480), the transformer primary is Wye configuration, which means 277v across each coil (to the centerpoint connection). To convert it to single phase, the center point must be disconnected, so the coils can be individually driven. This means each coil is 'expecting' 277v, but we only have 240v. The transformer operates fine at 240, but won't yield full voltage output at that drop... HOWEVER, I compensated for that drop by taking the secondary side (configured in Delta) and changed it to Y with the Contactor Mod... effectively bringing the output voltage back up to the same point as it SHOULD have been.

On the 200-230/460v machine, the coils have an additional tap on them to run down at 200v... well, when you disconnect the Y connection point, and utilize that 200v tap, it just so happens that the coils are practically perfectly matched to 240v... so it'll wire up, and operate just fine, without doing the 'contactor mod' on the secondary side.

As always, the FIRST step is to get the RIGHT DIAGRAM for your machine. Once you've identified it as proper, remove ALL voltage selection jumpers from the terminal strip... you won't need them.

Next, carefully unbolt the terminal strip from chassis and swing it out JUST FAR ENOUGH to be able to reach in with a pair of small end-cutters and snip off all the wires that we WON'T be using... first and foremost will be the jumper that ties all the coils together (the Wye connection). Compare your diagram to the machine's terminal strip, and you'll see it goes from one terminal of the upper group, to one terminal of the middle group, to one terminal of the lower group.

Now it's time to post some pictures... please stand by...
 
Step 1: Clean house

First step is to clear the stuff that's gotta go. This includes the Wye connection and the L2 connection. Look for these, and disconnect/remove. I suggest that you just locate and clip them off with cutters, rather than try to remove the nuts from back side of the terminal strip.

Here's what it looks like from the factory diagram, and what it'll look like AFTER cleaning out those things.
 

Attachments

  • cp-300 200v mod before.JPG
    cp-300 200v mod before.JPG
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  • cp-300 200v mod step 1 - clear unnecessary.JPG
    cp-300 200v mod step 1 - clear unnecessary.JPG
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Step 2: Configure coils for 240v

Next step is to install jumpers on the terminal strip to make each coil good for our 'target' input voltage of 240v. This means for each coil set (A, B, and C) we'll use two of the connection points that were previously for 200v 3-phase operation... here in luminous Green.
 

Attachments

  • cp-300 200v mod step 2 - 200v wiring.JPG
    cp-300 200v mod step 2 - 200v wiring.JPG
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Step 3: Connect capacitors to coil B

Next, we'll connect capacitors (with bleeder resistors attached) to the B coil 'driven' windings (blue lines) and feeding the capacitors with 240v hot from the A and C coils (black, and red lines, respectively...:
 

Attachments

  • cp-300 200v mod step 3 - Capacitor wiring.JPG
    cp-300 200v mod step 3 - Capacitor wiring.JPG
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Step 4: Connect main feeds

And last, connecting the remaining two hot leads to A and C (black and red wires)
to the existing coil connections' 240v mains power...
 

Attachments

  • cp-300 200v mod step 4 - 240v mains wiring.JPG
    cp-300 200v mod step 4 - 240v mains wiring.JPG
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Step 5: Connect mains

After that, you SHOULD be able to connect L1 and L3 to the 240v leads of an ordinary 'range plug', or whatever feed you have of 240v single-phase power... and turn it on for a test!!

And for those of you that said "Wait- you didn't do the 'contactor mod' of the other CP...

...That's correct, we didn't. Reason being: It isn't necessary.

The 230/480 Y arrangement illustrated in other conversions does not have a 200v winding tap. As a result, the only option I had was to power each coil (that was wound for 277 per coil, in Y... comes to 480) with a bit lower voltage than it was 'expecting'. That meant that the transformer's OUTPUT would be a few volts low. The contactor mod compensates for that...

But on this 200-230/460 machine, I wired the 200v taps in series to result in coils expecting just a sniff shy of 240v (because 200v Y equates to 114v per coil... which when placed in series... is 228v... which means 240v mains will be pushing it 12v HIGHER than design... but 12/228= 5.25%... so well within +/- 10%... and still within reach should line voltage reach 250v.

SO... it should work just dandy as-is...
 
Dave,
I have a CP-300 200V/230V/460V wired up this way and have put up to 180uF per leg. The open circuit voltage only gets to 34V. My capacitors are 60/5uF so I can trim up to 195uF, or am I just better off tracking down 80uF or 100uF capacitors.
Thank you,
Jon
 
One thing to add I know I am getting the right voltage across the primary coils because the remote sockets are providing 24/120VAC.
 
John... if you're getting to 35V on open circuit, I think you're doing more than okay... you might get enough heat to weld a concrete block to the surface of the sun... Put some wire in the feeder and try it.

It's important to realize that when you measure voltage across the coils, the reading you're getting will be largely irrelevant... particularly when you're not actually welding.

The reason this is the case, is because that center coil and capacitors constitute a rather 'complex reactance'.

If you do a 'pure' model of just a coil and capacitor (a 'tank circuit') at a fixed frequency, you can calculate impedance, thus current and voltage... and because of the circuit being a resonant device, you can throw Kirchhoff's Law right out the window.

...but this isn't just a coil. The coil, since it's core is physically SHARED with two others, changes in it's personality when in operation... it become's a moving target, based on how magnetic flux circulates through the core.

What matters, is that there's current flow through the middle core... enough at the low end to 'start' the circulation, and not so much at the 'high' end to cause saturation problems. My experimenatation suggested that there's such a forgiving nature of these cores and coils, that it's hard 'not' to make it work well, and it's seemingly next to impossible to saturate anything. I'm certain that eventually, someone will find a way to make it happen, but I haven't found that limit yet.

Do the conversion, put on torch and leads, and burn wire. Don't worry about the meter, don't try to make finite sense of it... just strike an arc and fiddle with the voltage and wire speed.
 
Dave, thank you for the response! I just fixed my suitcase feeder and will test it hopefully this weekend. I will back off the capacitance to 130uF - where it was happy using the 460V taps on the primary and wye modification at the contactor. The good news is the clicking at the contactor went away completely when using the "400V" tap schematic above.
 
I realize this is an older thread, but I just started converting a CP-300 with S-54a feeder. The thing ran fine on my rotary converter, but now it acts like it's getting low voltage. The fan motor barely turns. The feeder does feed wire and the contactor pulls in solid when triggered, but the fan isn't going to cool anything barely turning. I tried flip floping my 120uf capacitors, and that made the situation worse. The coils are getting 240v ea on the feeds.
 
B.Reilly, the fan wiring need to go directly to the black and red leads in the pictures above, which is either the second and fifth terminal on the left or right coil in the schematic above. I didn't quite understand what you meant be swapping capacitors, but if you follow the schematic above and change the location of your fan wiring, you should be good. As soon as I figure out how to post pics, I will show you where I connected mine.
 
B.Reilly, the fan wiring need to go directly to the black and red leads in the pictures above, which is either the second and fifth terminal on the left or right coil in the schematic above. I didn't quite understand what you meant be swapping capacitors, but if you follow the schematic above and change the location of your fan wiring, you should be good. As soon as I figure out how to post pics, I will show you where I connected mine.

Thank you, I'm assuming the connections for the fan motor are on the back of the terminal strip?

EDIT: Also I left the connection between L2 and the center transformer core (wire 9 I think) - L2 isn't connected to anything, so I didn't see a risk with this. Do I need to locate and remove that connection as well?
 
Hi B.!

Yeah, the fan motor connections are frequently landed on the BACK side of the terminal strip.

MY experience has been that it's best to just very-carefully-snip off those wires, rather than disconnect the terminals... and install new ring terminals and connect them at the FRONT... because disturbing the terminal connections on BACK tends to result in broken transformer wires. Moving fan to the front becomes really easy and obvious once you've got 'em clipped off.

The unused leg is just that- unused. If the wire you're using is connected to the power-transformer side, you can disconnect it at whatever terminal it's landed to, or cover it with a piece of shrink-wrap and eight-ten turns of good electrical tape, then secure it somewhere benign.
 
Okay, got the fan motor moved, and now it SOUNDS like it's running well, but I struck an arc with the same settings that worked before and it's running super cold. The wire is just stacking on top. I was expecting that it was going to be closer after conversion. Is this to be expected? What voltages should I be seeing at the contactor? Would the other conversion (with the contactor mod) be better for full output?
 








 
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