Rotary Phase Converter Problems

Erikflor · Jun 27, 2015

I recently purchased a rotary phase converter to run a small CNC lathe in my shop. I wired it to the 220 single phase panel yesterday, flipped the switch and nothing good happened. My best explanation is that it quivers...like it turns back and forth but won't make up it's mind about which direction to turn. I tried over and over but continue to get the same results. I have also wrapped a string around the motor shaft to give it a spin before flipping power on, same results.

I'm not sure how big the motor is because it has no plate but my best guess would be 15hp. I have always used VFD's so this is my first run with a RPC. I'm wondering if I need to replace the magnetic controller??

9100 · Jun 27, 2015

I don't see any capacitors in the pictures. If you apply single phase to two legs of a three phase motor, it will exhibit the symptoms you describe. You should be able to rope start it, but you may not get it spinning fast enough. At least a starting capacitor is needed to self start.

You might be better to post this in the transformers, phase converters and VFD forum.

Bill

lowCountryCamo · Jun 27, 2015

Is there more to it than in the pictures? Most rpc's have capacitors banks. When built my rpc I mistakenly put single phase power to all three legs instead of two and it quivered like that. I realized my mistake after a moment.

JST · Jun 27, 2015

Looks like a bit of a mess.... lots of taped wires, things hanging loose, etc. Needs cleaned up bigtime.

The actual problem is likely to be the start circuit (you knew this, right?

) There should be a set of capacitors which are temporarily put in circuit to phase shift the 3rd wire and get the idler motor turning. I was going to say they may not even be present, but they are at the bottom under the dust, with the orange wires.

I see that the orange wires go noplace, though, so they do not look connected. There does appear to be one black wire going someplace, so one connection may exist.

That thing is such a mess, with loose wires, taped up stuff, the big "blob" in the middle, and missing wire protection on holes thru the chassis.... I'd hate to even try to give specific advice about it from what I can see. Looks like you may have got "sold a pup". Maybe it's a pup that can be made into something, but it's hard to tell what's even in there now.

I see a contactor, capacitors, something in a black case that must be the potential relay, and I assume the box is mounted to the motor. But teh wires are a disaster area, looking like the results of an explosion.

Bob-J-H · Jun 27, 2015

You need a starting capacitor, and a way to take it out of the circuit after starting.That is some nasty ass wiring. It needs to be cleaned up to figure out what you have there. Bob

Erikflor · Jun 27, 2015

Start capacitors are sideways on the bottom of the box- I pulled one out (the two unconnected wires) to get the information off it in the case I need new ones. The wiring is a mess and is something I will clean up, I will also be putting the missing start capacitor back in.

I bought the thing from a guy that I consider to be reliable, he actually told me that it occasionally had this problem on startup. His remedy was to shut it off and then turn it back on...this isn't working for me. I just ordered a new set of start capacitors and will be cleaning up the wires, assuming it is currently wired correctly- is there anything outside of weak start capacitors that would cause this type of behavior?

JST · Jun 27, 2015

Anything that prevents a good capacitor of the right value from being connected during start along with good input volts..... That's kinda open-ended, but....

Bad caps. bad wiring, bad connections, bad potential relay, etc.

The shut off and turn on "fix" suggests a bad connection or a balky relay. Maybe it has become fully "open" now, instead of intermittent.

James H Clark · Jun 27, 2015

Erik: Even if you get it to run, I would be reluctant to use it for a CNC machine. Most CNC's are sensitive to the voltage levels. Use it at your own discretion. Good luck.

JH

jim rozen · Jun 27, 2015

"I recently purchased a rotary phase converter to run a small CNC lathe in my shop."

Return this for a refund. Given the symptoms (does not work) I'd hazard a guess that
it is defective merchandise. You need to get your money back.

Erikflor · Jun 28, 2015

James H Clark said:
Erik: Even if you get it to run, I would be reluctant to use it for a CNC machine. Most CNC's are sensitive to the voltage levels. Use it at your own discretion. Good luck.

JH

It's the best option I have right now. I have read that this machine does OK with a RPC, ideally I would have a 3phase line run to the shop but I don't live in an area that has this option.

I pulled all the capacitors yesterday and cleaned up the wiring. With no capacitors in the circuit I applied power to the RPC, same results. I'm replacing all the start capacitors as my first step and will proceed from there if needed. I don't have a lot of money into the thing so I can live with replacing items to get it running properly.

WHHJR · Jun 28, 2015

A better option IF you want an RPC try here; WNY Phase Converter & Supply .
They may not be quick, but their stuff work and is reasonable.

4¢

swatkins · Jun 28, 2015

That mess looks like a fire just waiting to happen.. Since you already have the motor, hardest part to source, I would just rip the controls you have off and install a new control box. Simple, fast, not to much money and a heck of a lot safer. I bought my control from this guy. He rated it for CNC and so far I've had no problems.

This is the one I bought.

rons · Jun 28, 2015

JST said:
Looks like a bit of a mess.... lots of taped wires, things hanging loose, etc. Needs cleaned up bigtime.

The actual problem is likely to be the start circuit (you knew this, right? ) There should be a set of capacitors which are temporarily put in circuit to phase shift the 3rd wire and get the idler motor turning. I was going to say they may not even be present, but they are at the bottom under the dust, with the orange wires.

I see that the orange wires go noplace, though, so they do not look connected. There does appear to be one black wire going someplace, so one connection may exist.

That thing is such a mess, with loose wires, taped up stuff, the big "blob" in the middle, and missing wire protection on holes thru the chassis.... I'd hate to even try to give specific advice about it from what I can see. Looks like you may have got "sold a pup". Maybe it's a pup that can be made into something, but it's hard to tell what's even in there now.

I see a contactor, capacitors, something in a black case that must be the potential relay, and I assume the box is mounted to the motor. But teh wires are a disaster area, looking like the results of an explosion.

A pull start didn't work. So start capacitor(s) are not the main issue.

JST · Jun 28, 2015

rons said:
A pull start didn't work. So start capacitor(s) are not the main issue.

Can't you see where I TWICE said they are visible? Jeez.

I reckon the crazy wiring is still the issue, or part of it. We didn't at that point know if the motor would even run, or if it was wired close to right. And we still don't, since it does not seem to have run YET.

We don't know if the spin start would work if the existing capacitors were NOT in circuit.

It's time to wire to that motor straight, and check it out on pull start.

In fact, it's well past time to have a squint at the motor label.

Erikflor · Jun 28, 2015

A motor label would be nice but I haven't found one yet and there aren't too many places to hide one.

I cleaned the wiring up a bit- no bad connections that I've found so far. Wish I understood the wiring a little more.

JST · Jun 29, 2015

Normally they are on the motor, but as that is probably a special-made motor, it's entirely possible that it never was on the unit.

Failing that, how about the label for the entire thing.... for the RPC itself? There must be some sort of ratings label on it somewhere, so long as it was made by an actual company, with agency approvals.

9100 · Jun 29, 2015

Motors specially designed for RPC service often do not have external shafts, so this one probably was made for another purpose. The first thing I would do is find someone with three phase who will let you test the motor on the proper power. It could simply be a bad motor. Replacing parts without a proper analysis is just wasting money.

Bill

JST · Jun 29, 2015

Checking the motor (or unit) voltage is a good first step.

Then verifying good motor windings, with an ohmmeter. All pairs should measure the same resistance. Some meters won't do a good job on the low resistance in a bigger motor, though.

You can disconnect the motor from the other "stuff" and try a "rope start" that way. Do that 3x, changing to a different pair of wires each time. If every time behaves the same, you can be pretty sure the motor is good.

If there is a difference, or it doesn't start, it;s time to detail check the connections. See if the connections make sense, or if maybe there is one coil hooked backwards.

jim rozen · Jun 29, 2015

"The first thing I would do is find someone with three phase who will let you test the motor on the proper power."

Why?

If I bought a TV set and it blew up when I plugged it in, I would not try to fix it.

He paid money for a bogus piece of junk. Return it forthwith to the seller and request the money back.
Does not even come close to being useable for its intended purpose. No damn good. Busted. Probable
outcome when trying to use it, the house burns down.

Where DID this thing come from??

JST · Jun 29, 2015

What most are suggesting is to find out "if the tv really did blow up". Meaning if the motor is any good.

If not, it's an expensive anchor, return the piece of crap for refund.

Crappy wiring, on the other hand is common enough, and not so hard to fix. You'd want to check it in any piece of used equipment.

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