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Rotary Phase convertor

praska86

Plastic
Joined
Oct 27, 2017
First off I love this forum I have read and learned a lot on here. First time poster so giving it a whirl. I have been wanting to build my own RPC for awhile and have been on the search for a idler motor and recently i can across a complete rotary phase convertor. My question is does any one have any insight into how this is wired? I asked the seller but they acquired it at auction from a reliable local machinist and haven't used it and didn't know much about it. I suspect by looking at it that the pony motor is continually providing power to the idler. Can anyone tell me if I am wrong or provide some insight into it.

Also would be helpful if i Do buy it what can i do to improve it?

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Thank you in advance for all your help
 
I suspect by looking at it that the pony motor is continually providing power to the idler. Can anyone tell me if I am wrong or provide some insight into it.

Also would be helpful if i Do buy it what can i do to improve it?

View attachment 211434

A closer look at what looks like a relay (lower right) would help. Pics of both motor nameplates would help too.

The builder decided not to use the fuses. Not too intelligent.
 
My hunch is that it is probably set up with the relays inter-connected/sequenced so that while the start button is held, the small relay turns on the pony motor, and the small relay then also activates the second larger relay, which may be wired in a "self hold" once energized -so that when the button is released, and the small relay drops out, power is cut to the pony motor, but the large relay stays on, tying the larger motor to the power in/ 3ph out- and then the kill button would interrupt the larger relay's coil so that it would drop out. BE REALLY CAREFUL because it is possible that some portion of the outputs could remain live even when the relays are not actuated (before start up), or after the off is hit (after the large motor spins down). My RPC which someone (unknown exactly who) built- and designed and built pretty nicely- leaves single phase still feeding through to what should be the 3 phase output, even after hitting the off switch and the large motor has spun down- until you throw a main manual 3 pole switch that cuts everything off. Agreed with the other comment that the fuses belong in the output, and I'd recommend fusing or a breaker on the input, too. Assume nothing until you check over the whole thing, prior to operation, during operation, and after operation. Make sure any housings are all securely grounded to the safety ground (amazed how often I find DIY people didn't do that)(I am a DIY but I prefer to not have an E take the place of the Y). Even after checking over before powering up, in the beginning, the old timers' one hand rule is not a bad idea- only ever let one hand contact or come near anything (even outer housings) and keep the other hand totally away from the device and anything else conductive- that way if you contact something that turns out to be live, the shock will be localized and not pass through the main part of your body. You should be able to systematically follow the wires and sketch up a diagram of how it is set up and how it ought to behave. This stuff isn't dangerous if you are methodical and prudent, but it is nothing to mess with casually.
 
It would be better if the start motor disconnected from the main motor. But not with that coupler.

The 709 is missing something. What is it?
 
How many conductors are in the power cable, two plus ground or 3 plus grd. It appears that if three wires, there should be a knife switch with fuses Large enough to run the Machines, Phase gen as well as the start motor. This switch wound have 3 poles, poles one and three are power from main panel.the output of the switch, wires 1, 3 go to the starter motor relay AND the Phase gen. The third wire from the phase gen goes to the #2 INPUT side of the knife switch. Now the #1, 2, 3 output wires are each fused for the in the box are where you hook up the machines with the 3phase.

What concerns me with the start stop switch,as it appears is that the Gen side will be energized on two phases, as soon as power is applied, although the start button has not been pushed as yet. Better wire it so the pony motor begins to run at the time power is applied to the box through the knife switch. And the off button would drop the starting motor.

Maybe make a diagram of the wiring we could better understand.

If its two plus, then it appears that the load connections are to be made in the box.Will those fuses in the box are
 
From what I see, it doesn’t look like that bad of a design.

Pressing on the start button does two things, three wire control hold circuit for the main contactor and momentary start for the pony motor Contactor.

My guess is you would have to hold the start button for 2-4 seconds. Once you let go of the start button, the single phase motor drops out. And the three phase motor keeps running.

The coil voltages seem to be 110 V. So, you will need to wire it with two hots a neutral + ground.

Is the pony motor 220 V or 110?
I would just fire it up and with a clamp on metre check your amps during start up. I could give a few more suggestions on self starting, but if you have a working unit, why reinvent the wheel?

Show us a picture of the motor name plates. I don’t see an out feed wire, so, I suppose the fuses were probably used for outfeed.

Once you get voltages, after it’s up and running, you might be able to add a few run capacitors for balancing. This will assist in starting too.

The only thing I don’t like (or I think, I see I don’t like) the 110 V pony motor is using ground as it’s neutral. But, with a pictures of the motor tags, and showing a plug or how many wires are in the feed line (but I’m pretty sure I see both a ground wire and a common wire that feed the pony, both screwed down to the back panel). If I’m right this is a no no.
 








 
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