Roatary Phase converter ??

[muddstopper]

I have the opportunity to purchase a 1947 brown and Sharpe Vertical mill at a extremely good price. Problem is it needs 3phase power and of course I dont have that and couldnt even afford to have it ran to my shop. I contacted a manufacturer of one of those Box converters, which at first look seemed like the perfect (and cheap)solution. The manufacturer said he wouldnt recommend that type of converter for this machine simply because the old 3phase motors ( there are 3 motors on the mill), on it where not compatible with a static phase converter. He said the machine would run off one, but it would only be a matter of time before one of the old obsolete motors would burn up. Since changing out the current motors would require finding 3 single phase motors, I figure it would just be easier and probably cheaper to build a rotary phase converter out of a old 3phase motor. Of course I am used to seeing those old 3 phase motors laying everywhere until now that I want one, so I am still searching for one. Watching Utube I have seen several ways to make it work using all kinds of compacitors, but the method I really like just uses another single phase motor to start the 3 phase motor to rotating and then turning the single phase motor off. Problem is, just watching those videos, none of the authors are clear as to whether or not they still need run capacitors to make the rotary phase converter work. It looks like just hook up 220 to 2 legs of the 3phase and get the motor turning and you have the 3phase power coming out of the motor that you need to run your other 3 phase equipment. So, if anyone here has ever build or uses a rotary phase converter to run their 3 phase equipment, I could use a little advise before I start spending money

 

[Sawyer Rob]

My BIG drill press and lathe are 3 ph. (also a couple other motors) so, I was going to build a rotary phase converter, as I have several 3ph. motors laying around here... But, when I looked around, I found a guy not too far from here, building them and selling them with a war., so I bought this one,

I just push the button and it starts, then I start what ever 3 ph. motor I need to use...

I don't regret having spent the $$ to get one "properly made" at all...it works every time and has had zero problems with zero maintance...

SR

 

[muddstopper]

I looked at the store bought units and thought about just buying one, but hard heads being what they are, I thought I would just build one using old parts. Probably not the smartest thing to do, but they dont look that complicated and half the price of the store bought ones is in the actual motor. There are plenty of old 3 phase motors around from all the manufactoring plants that have shut down and I dont think its going to be all that hard to find a motor. Actually found a 25hp motor this morning for free, but I think that size would be over kill for running just one machine. a 1.5 hp converter is around $550 but wouldnt be big enough to run the 5hp mill. I would need around 7.5hp to provide full power and a converter that size is over $800. My weird thinking is telling me to go oversize in case I want to buy some other 3phase equipment in the future so I would probably be looking at a 10 or 15hp converter and now you getting over $1000. There is plenty of good reasoning for buying ready made, but my bank account is telling me I better build my own.

 

[newbury]

If you have not found it yet Practical Machinist has a LOT of info on building your own. I'm in the same situation. I bought about $1K worth of 3 phase tools:
about 2 years ago. Based on comments at OWM (old woodworking machines) and Sawmill Creek just the planer was about worth that.

Everyone bragged that one could easily pick up a 3 phase motor for a converter for $10/HP. BS. I searched for over a year before I found a 10HP for $150 in good shape.

There's a good seller on ebay, Phase-Craft, that seems well respected and sells everything but the motor for a 10hp unit for $220. Thus for about $400 I should be able to put together a unit. BUT due to a 1,000 other things I've not gotten around to buying that and hooking it up, hopefully this fall.

I read and viewed a lot of guys just running one by starting it with 220V and a rope. Not the safest but might do.

 

[kennyd]

I contacted a manufacturer of one of those Box converters, which at first look seemed like the perfect (and cheap)solution. The manufacturer said he wouldnt recommend that type of converter for this machine simply because the old 3phase motors ( there are 3 motors on the mill), on it where not compatible with a static phase converter. He said the machine would run off one, but it would only be a matter of time before one of the old obsolete motors would burn up.

I assume your talking about a VFD or "Variable Frequency Drive"?
I have one on my 1959 Bridgeport 1hp mill, and my 1969 Clausing 1hp lathe, and the 2x72 belt grinder I built. IMHO what the rep was saying is only partially true, its not a problem if you run them at 60hz or close to it like 40-80hz, its when you get extreme that causes problems-that's when you change the belt position on the machine. I would not want the RPC in the shop, the extra noise, expense (wire, plugs, disconnects and distribution panels if doing it for multiple machines), and real-estate is not worth it to me, plus the ability to fine tune the machine's speed is a huge advantage.

 

[woodchipper]

I used to run my machine shop on 220V volts by running a 5Hp Rotary Phase Converter coupled to a step up transformer. I would run all my tools no problem, as long as I would run them one at a time. No three machines operating at the same time due to the limit of what the phase converter could produce. It is the start up of the motor that requires much more power than its plate rating.
I would just go to a local motor rebuilding facility, and get a quote. Some still have decent prices for quality workmanship.

 

[Sawyer Rob]

I looked at the store bought units and thought about just buying one, but hard heads being what they are, I thought I would just build one using old parts. Probably not the smartest thing to do, but they dont look that complicated and half the price of the store bought ones is in the actual motor. There are plenty of old 3 phase motors around from all the manufactoring plants that have shut down and I dont think its going to be all that hard to find a motor. Actually found a 25hp motor this morning for free, but I think that size would be over kill for running just one machine. a 1.5 hp converter is around $550 but wouldnt be big enough to run the 5hp mill. I would need around 7.5hp to provide full power and a converter that size is over $800. My weird thinking is telling me to go oversize in case I want to buy some other 3phase equipment in the future so I would probably be looking at a 10 or 15hp converter and now you getting over $1000. There is plenty of good reasoning for buying ready made, but my bank account is telling me I better build my own.

Mines a 7.5hp, I paid $250.00 for it...

I have a 25hp motor here, but shipping would be a bear!

SR

 

[muddstopper]

Well, the $250 price, if thats for a complete rotary converter, beats what I have been seeing, and I have to pay shipping no matter who I buy it from. Give me the guys contact info, PM if you dont want to post it in public. And I will give him a call.
I have a buddy, actually the guy that offered me the deal on the mill, is running 5 machines at a time off his homemade rotary. His is a 20hp 3phase motor. I asked him about how his is built, but he had someone else build it and is as ignorant as me on this subject and doesnt know how it works.

The only reason I am thinking about getting a big converter is because i am considering upgradeing my current lathe (1928 A model Monarch) to something a little newer. I could probably still get buy with a smaller converter, since 99% of the time I am a one machine at a time guy, its that other 1% when I try to multitask that I usually screw something up.

 

[Mysfyt]

I'd encourage you to go ahead and build that rotary converter. As was mentioned, search Practical Machinist to get your ideas on how elaborate you want to get with it. You'll have fun building it and learn a lot about electricity in the process. Just my .02

 

[muddstopper]

I'd encourage you to go ahead and build that rotary converter. As was mentioned, search Practical Machinist to get your ideas on how elaborate you want to get with it. You'll have fun building it and learn a lot about electricity in the process. Just my .02

I dont know if I need any encouragement:laughing: Leaning that way already, but if I can get a ready made converter for $250, I'm not sure I can build one for that amount, even with a freebee donor motor.