Rotary phase converter to build or not to build.

Pottsie454 · Apr 19, 2016

Looking around this forum I am at a cross roads of weather or not to build my own rotary phase converter panel or to just buy one from pheonix phase converter. I already have a 30 hp 3 ph motor I have been test firing with a rope pull and all is well. Now im on to the balancing act.

What is your all opinons on buying a kit like pheonixs or just building your own. Do you really achieve better performance from them, is it cheaper in the long run? I have no problems building my own. To attest to my nerdism I have a 4 channel o scope. Just didnt know if you could build the 30 hp version for less than 500.

Thanks for the advice!!!

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swatkins · Apr 19, 2016

For me it all boils down to a simple question. Do you want to spend your time on a project or do you need to make chips?

If you're good with electrical work the quality of your shop made box can be just as good.

Even though I could have easily built my own box the time I would have spent sourcing the components would have cost more than the money I saved building my own.
When I ordered my second box it was here , and ready to go, in 5 days...

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rons · Apr 19, 2016

$2245 + $95 shipping. (push button controls and digital protection options included)

I would build my own rotary, otherwise..
I am looking at the Phase Perfect these days. No idler motor, so it is quiet.

BTW: what are you going to drive with a 30hp rpc.

kgize · Apr 19, 2016

You already have the 3 phase motor, you already (I assume) have some electronic knowledge if you have a 4 channel oscilloscope. It is a 'no-brainer' that should build your own unless you have money to burn. RPCs are a relatively easy project with lots of information and design specs on the internet. Buy a variety of suitable capacitors on ebay and using your oscilloscope and a little trial and substitution of the caps, you can get a better balance of voltages for your specific application than any off the shelf RPC. Of course you could do the same to a purchased RPC..But you already have the motor - that's the primary part of an RPC.....go for it on your own....

Pottsie454 · Apr 19, 2016

Thanks for all your responses. I looked at the cost of everything involved to make a safe easy to use converter. At the 30hp range it would cost roughly $380 for the caps, switches, and relays. Adding in the cost of connectors and wire you getting close to the $500 mark... then you have to put it together. Considering it all I decided to buy the Pheonix Converter Panel and fix what ever might fail in the future. I assume at the price point they are at it would be the harbor frieght of converters.

Ill keep you posted on how it turns out!

Also, btw I plan on running the converter to run my bridgeport, southbend lathe, hendey lathe, gorton horizontal, rockwell drill, powermatic band saw, custom mitler brothers bead roller, delta radial arm and table saw. Maybe not all at the same time, but ive been know ln to multitask.

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rj1939 · Apr 20, 2016

Even with "multi-tasking" you have some serious overkill. I'm guessing that a 10 hp would run any three of those machines at the same time.

Danny VanVoorn · Apr 20, 2016

rj1939 said:
Even with "multi-tasking" you have some serious overkill. I'm guessing that a 10 hp would run any three of those machines at the same time.

Agreed; I have a 2 three horse power converters ( one in my shop and the other in the basement shop area) and a two horse in the attached garage and they do all I ever need. I run a 13" lathe, and 2 Deckel mills on one often at the same time. Have started an antique 5 horse power shaper with one of them with no problem so I think 30 HP is a lot. Now some of my high demand equipment is single phase such as the air compressor, if 3 phase I would need bigger?
Dan

Pottsie454 · Apr 20, 2016

Everything I do, I do with over kill. Granted 30hp might be to big right now, but I am constantly buying equipment so in the future I might utilize it better. Plus, with a 30hp you can run a 50 amp resistive load which would be sweet for a welder. I see 3 phase welders go for scrap prices because home gamers cant run them... now I should be able to.

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Pottsie454 · Apr 20, 2016

Also, by the by, the gorton mill has a 7.5 hp spindle, 3 hp feed, and a 1/4 hp coolant pump... just starting that thing up would be asking alot from a 10hp phase converter.

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Grigg · Apr 20, 2016

Mills usually start easy because both the spindle and feed motors are pretty much unloaded at startup. I think 10HP would do you fine.
Although 15 or 20hp might be better in the long run. 30hp sounds like overkill but could one day be necessary depending on what you expect to buy. For example a 15-20HP air compressor would be happy with a 30hp converter.

cgrutt · Apr 20, 2016

Probably not going to be much help but wanted to chime in because I'm in the middle of building my own RPC for 7.5 HP idler motor. Not sure why many people claim its cheaper to build your own, I found quite the opposite to be the case. Hoping I wind up with better balancing and better components but not sure that will be the case from what's available now. I enjoy working on projects so don't mind but I'm at about double the price of a new assembled one and I haven't finished it yet. Also just wanted to say to make sure you use the correct rated wire and components for a 30 HP idler. Not sure what that will draw but it's got to be upwards of 60-70 amps with higher demand under load and startup. Be safe and good luck!

JST · Apr 20, 2016

The cost of building your own, in parts, not your time, is mostly in what the motor costs you. A nice new motor with associated parts and a box can get expensive through a builder of RPCs. If you have a suitable motor, or can get one at very low cost, it makes sense to build it in some situations. At least to use a "box builder" to put together the control box, so all you need to do is wire it up to the motor. You wiill probably want to get the box from a shop that is UL 508 qualified, so they can sticker it.

If you are going to spend bigger money on the motor, AND buy a pre-made box, you ae getting close to just buying the whole thing from a phase converter company. And if you consider buying the whole thing, it may make sense to look at Phase Perfect, since their output is a "no-excuses good" balanced power, almost "install and forget".

Building the control box probably makes little sense for many folks, as it is a lot more work, meaning non-productive time spent.

cgrutt · Apr 20, 2016

JST said:
The cost of building your own, in parts, not your time, is mostly in what the motor costs you.

Wasn't for me. I bought a used motor on CL for $100. New caps and resistors were $205 (after 20% discount), Contactors, potential relay and wiring strip was $116 and wire was about another $100. Still need to buy a box to put it in, figure another $50 - $75. This is just for a 7.5 HP unit. Prebuilt box without the motor was $229, so I'm at about twice the cost of a pre made unit. I know it would have been cheaper to source used and/or surplus parts but I take comfort in buying this stuff new when it comes to electricity.

JST · Apr 20, 2016

cgrutt said:
Wasn't for me. I bought a used motor on CL for $100. New caps and resistors were $205 (after 20% discount), Contactors, potential relay and wiring strip was $116 and wire was about another $100. Still need to buy a box to put it in, figure another $50 - $75. This is just for a 7.5 HP unit. Prebuilt box without the motor was $229, so I'm at about twice the cost of a pre made unit. I know it would have been cheaper to source used and/or surplus parts but I take comfort in buying this stuff new when it comes to electricity.

That's the point, it WOULD have been had you bought the motor new..

If you can get a super deal, that changes things. Your actual price is even more than you state, as your time is worth something also. "If you have a motor, or can get one at very low cost" is what I said might make it sensible to build it yourself, obviously because that offsets the price of your time, and the total all-up price may be substantially less than buying an actual RPC.

cgrutt · Apr 21, 2016

OP already has a motor. My point is that its not necessarily cheaper to build your own RPC (ex motor) vs buying one off the shelf but you may choose to do so for a variety of reasons. At least i think that is what he was asking...

rj1939 · Apr 21, 2016

Don't know if anybody has an outlet like this, but a motor shop we deal with had some 3 phase motors that had chewed up keyways, they were selling pretty cheap..............perfect for rpc's.....that was a while back.

rons · Apr 21, 2016

JST said:
The cost of building your own, in parts, not your time, is mostly in what the motor costs you. A nice new motor with associated parts and a box can get expensive through a builder of RPCs. If you have a suitable motor, or can get one at very low cost, it makes sense to build it in some situations. At least to use a "box builder" to put together the control box, so all you need to do is wire it up to the motor. You wiill probably want to get the box from a shop that is UL 508 qualified, so they can sticker it.

If you are going to spend bigger money on the motor, AND buy a pre-made box, you ae getting close to just buying the whole thing from a phase converter company.

Building the control box probably makes little sense for many folks, as it is a lot more work, meaning non-productive time spent.

what a bunch of MALARKEY. Like comparing a cheap econo box car built in Korea with the door panels fastened with glue and
a Shelby Mustang.

Pottsie454 · Apr 21, 2016

Rated FLA for my 30hp is 78 amps. I have a dedicated 200 amp service for the 3 phase conversion.... starting amos wont be an issue. Im just hoping idling amps are under 10. When i rope started it, it was drawing 35amps per leg on single phase. Im hoping the run compaciters help bring that down.

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Jim McIntyre · Apr 21, 2016

Pottsie454 said:
...When i rope started it, it was drawing 35amps per leg on single phase. Im hoping the run compaciters help bring that down....

Yes - you can reduce the idle current with proper capacitor tuning. But, that won't affect your power bill because (with single phase service) you buy energy from the power company, not amps. Reducing idle current is still a good idea, but don't think it's going to cut your power bill by 2/3 or something...

Pottsie454 · Apr 21, 2016

Jim McIntyre said:
Yes - you can reduce the idle current with proper capacitor tuning. But, that won't affect your power bill because (with single phase service) you buy energy from the power company, not amps. Reducing idle current is still a good idea, but don't think it's going to cut your power bill by 2/3 or something...

How would one go about estimating the cost? I just checked my power companys rate schedule... $.101 kWh.

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