Rotary Phase Converter Questions

[Matt Hutchinson]

Ok, so I recently purchased a 10hp RPC panel. It was supposed to arrive with instructions, but there are nothing but a couple labels. I have yet to purchase and idler motor, but was hoping someone could give me some info on connecting everything properly.

Right now there are three terminals labeled "To idler motor". Seems self explanatory, but what happens with a 6 or 9 lead motor? I know I need a 2 or 4 pole motor, but I am not sure what that means. Also, the terminals labeled C, A, B I assume are the output 3ph which will power my tools. What's the best way to split the output between 3 or 4 machines? Another subpanel? Thanks.

Hutch

[Rick Christopherson]

You bought a rotary phase converter that doesn't come with a motor? That may be fine, but it does leave me a little concerned. If it is just a static converter, then simply adding an idler motor does not constitute a rotary converter.

Regardless what type of motor you have, there will only be 3 power leads. It makes no difference what speed the motor is or how many poles it has.

If you have only one tool, then it is fine to just parallel the tool motor with the idler motor. If you have more than one tool, then the only output you take from the converter is the generated leg, and the two house-power legs should come from a larger circuit breaker (Electrically it is the same, but the circuit breaker can be larger.)

[Chip Lindley]

A rotary phase converter *panel* is quite different from a static phase converter. The *panel* IS all that an RPC IS, except the user provides his own motor.

All RPC literature I have read, indicates that a 1750 rpm motor should be used with rotary phase converters. Attached is a wiring diagram from a 10hp Panel I was considering on eBay. Perhaps it will help. Remember to connect to the low-voltage 220V leads of the idler motor.

[Scott T Smith]

What's the best way to split the output between 3 or 4 machines? Another subpanel? Thanks.

Hutch

Hutch, in my last two shops the rotary phase converters have been used to feed 3-phase load centers, and my equipment in turn was wired to the load centers.

Rotary phase converters can be ganged together if needed to provide additional power. By feeding a load center with them, in the future if you need additional power all that you have to do is add an additional converter and feed it back into the 3-phase load center.

[Matt Hutchinson]

Yes, the panel without the motor is what I purchased. It is a rotary phase converter, but I am providing the motor. It's cheaper that way, cuz I have a friend with a couple 10hp motors lying aroung.

As far as wiring goes, I think I have a better handle on it now. Yet I still don't know what a 2 or 4 pole motor is, or how to tell them apart. I did get a call from the person who made it, but I am not thrilled with how I have been treated and I wanted to see if I could use other trustworthy sources.

Right now I still have a few things to take care of before I can attempt to get it running. I just was curious to see who I might be able to rely on for help if I need it.

Thanks.

Hutch

[Mike Henderson]

Yes, the panel without the motor is what I purchased. It is a rotary phase converter, but I am providing the motor. It's cheaper that way, cuz I have a friend with a couple 10hp motors lying aroung.

As far as wiring goes, I think I have a better handle on it now. Yet I still don't know what a 2 or 4 pole motor is, or how to tell them apart. I did get a call from the person who made it, but I am not thrilled with how I have been treated and I wanted to see if I could use other trustworthy sources.

Right now I still have a few things to take care of before I can attempt to get it running. I just was curious to see who I might be able to rely on for help if I need it.

Thanks.

Hutch

For induction motors used in the USA, a two pole motor will run at 3450 RPM while a four pole motor will run at 1725 RPM. Look at the name plate to see what the operating RPM is for the motor you choose.

Mike

[Matt Hutchinson]

Alright, I get it now. That makes complete sense. Obviously I am not terribly well educated when it comes to motors. Thanks for the info.

Also, would anyone know if I could damage the load motor or the RPC panel electronics by attaching the wires to the generated three phase output incorrectly? (That is, the terminals labeled C, A, and B.)

Hutch

[Scott T Smith]

Common wiring is to use your single phase legs for A and B, and your generated leg for C.

[Charles Lent]

If you hook up a three phase motor and it runs the wrong way just swap 2 of the 3 phase leads to the motor. Then it will run the direction that you want.

The only load that you will need to be careful of which phase you connect is a load that has internal electronic or control circuits that run off 2 of the phases. If you have these, make sure NOT to connect them to the created phase. Motors by themselves do not care which lead connects to which phase.

Charley

[Matt Hutchinson]

Thanks for the info. Knowing that C is the generated leg really clarifies things. As far as I know, I don't have any machines that would be effected by connecting them to this leg. I do have a large 5 hp RAS with an electronic braking box attached, but I don't know that I will be able to make it work anyway after re-leading the motor for 230V.

Thanks again!

Hutch