Rotary Phase Converters - revisited

[DarkBlack]

VFD’s for larger motors like 5, 7.5, 10 hp, can still be run with single phase, with a 3-phase only manufacturer rating, but you must double the drive capacity, relative to the motor. In those cases it’s not as price attractive.

 

[JethroB]

Not in my rural area, if it isn't going right by you it is exorbitant to get 3 phase run in. I seen several shops with a few 3 phase motors that actually run a 3 phase generator to make power when the equipment is needed.

Same around here. Pricey to get 3 phase in from the rural power company. Lots of deep AG irrigation wells utilize 3 phase converters. We recently installed one to supply a new 6” well and it’s 40 HP pump.

 

[Handloader109]

I've a radial arm saw and a Delta lathe both running off their VFDs along with by current dust collector. No motor is over 2 hp. Used GE VFDs were cheap about 6 or 7 years ago and I picked up several at the time, sub $100. New were $150 to $200 for decent quality. I've looked at RPCs several times, but just haven't spent the money. Only the DC and one other tool would ever be run at the same time... but with anything over about 3 or hp, RPC is the way to go

 

[etpm]

Since the OP already has the 3 phase motors the remaining components should run less than $150.00 to make a Rotary Phase Converter that will start a 15 HP motor and run 40 HP worth of motors. I know all sorts of folks are sold on VFDs. I can see why too because I own several and they get heavy use. But they are all on machines that need variable speed. $150.00 to power his whole shop is a good deal. And no programming is involved.
Eric

 

[logixjock]

I've built a few, I'll see if I can find my notes. You'll need to scrounge up a bucket full of oil filled run capacitors, 330v or higher, a couple of start capacitors, a timer and a 3 pole contactor. Feebay is a good place to find used (cheap) stuff like that.

logixjock at 12345 dot com

 

[newbury]

Thanks for your continued interest. Life has gotten in the way again and I'm not making it down to Mississippi as often.
Look forward to seeing any notes you can scrounge up @logixjock.

 

[Patrick Herd]

Electrical engineer here: I've built a couple of RPCs too, including one that converts 230V single phase into 400V three phase as all our network distribution is 230/400V
Happy to answer questions on either RPCs or using VFDs and provide engineering perspective on either.

 

[CalG]

I used to run the shop tools on an assortment of RPCs. Biggest was 10HP for the big lathe.
When ebay was a real auction outlet, several VFDs were picked up at small cost. 35 and 45 amp TosVerts etc. Now I only have one RPC that runs the mill. With it's assortment of motors, It's just easier .

I use the package "phase-a-matics" to start the RPC idler.

That is an easy way to get a start cap and a steveco relay in a nice electrical box.
I used to futze with balance caps, but could never replicate any particular load combination to balance. So I've mostly given up on the notion.

It all seems to work. For the past 20 years......

 

[Mike sandor]

Best/most recent thread I found was Phase Converters

For those that may remember I've a shop with about 5 pieces of 3 (edit) phase equipment bought from an auction of the closing of a high school wood shop. Planer, bandsaw, tablesaw, radial arm saw, scroll saw. Had plans to build an RPC based on my son saying he would help. Bought a used but functioning 10 h.p. motor. And there was a guy on e-bay selling "kits" for a reasonable (~$150) price.
Then my son backed out. Then COVID came along. The ebay "kits" disappeared. So as life interfered everything just got stored.
So now it is all like a "barn find" and I'm wanting to start again.
I realize a lot of people will recommend "VFD's". But I'm also looking at getting other 3 phase equipment, recently got 2 more 7.5 hp 3 phase motors ($25@), and it seems there are now a lot of "Rotary Phase Converter Quick Build Kits" on the market for what seems to be reasonable prices.
So I'm looking again for any advice on recommended RPC kits.

I have a few machine tools that require 3 phase. The smaller stuff, Bridgeport mill and Clausing lathe, both run on a static converter. Drawback is you only can run one machine at a time and you loose a bit of power. Neither of which is a problem for me as I don’t push the machines that hard and only run one at a time. I have a CNC mill with a 5 hp spindle motor. This runs on.a vfd which is rated for 220 3 phase but in fact runs well on 220 single. I am currently installing a large universal mill that has numerous relays and transformers in the control panel. I purchase a 10 hp static converter but this will not fire up the control panel. The instructions that came with the phase converter also included direction to build a rotary converter using a slave motor to generate the third phase. Pretty easy to do, and it works well.

 

[dadohead]

In the late 70's my dad got a deal on a 5hp 3ph Powermatic planer. We looked into making a RPC even running down a 15hp 3ph motor but dad ended up buying a new Ronk RPC.

We had an electrician install the unit. Upon testing, the planer wouldn't run instead making a loud grinding noise with the cutter head barely turning (20 rpm?) There was nothing was wrong with the planer or bearings. After much troubleshooting and calls to Ronk the answer was "not every 3ph motor 'likes' a generated 3rd leg." The Ronk was returned and dad bought a new 5hp Baldor 1ph motor and controller for similar money.