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.

 

[Sawyer Rob]

First of all, that $250 was for a complete converter as pictured, but I've had it a few years and I'm sorry to say I don't know his contact info any longer. He was an electrical engineer putting them together for side money..... Sorry, I wish I could hook you up...

My point is, look around and "maybe", like me, you will find something you had no idea was even in the area.

SR

 

[Kyle_in_Tex]

Kenny, I think he was talking about static converters, where you lose 1/3 of your HP. The ultimate converter is a phase perfect, but very expensive.

The motor is half the money of a rotary usually. The box of capacitors for a 25hp motor costs about $500 last time I looked. If you do them right, they are not really noisy but kind of a white noise in the background. I need to buy just the box. I have the 25hp motor. It is just low on the totem pole of needs. I have a nice lathe I bought but can't use until I get some 3 phase.

Mudd, you need capacitors to balance your 3 legs.

 

[muddstopper]

Static converters are actually cheaper than $250, but that was not what I was talking about. I called a company that builds static converters and they flat out told me not to hook one to that old mill, or anything else 3phase that had a motor older than 1965. I dont understand it, but if the manufacturer doesnt think its a good ideal, I aint stepping out on my own and using one.

My $250 reference was if I could buy a complete rotary phase converter for that kind of money, it sort of made building my own seem kind of foolish. Now that I know I probably aint going to find a complete converter for $250, I'm back to trying to figure out how to do it myself, again. One thing to note is I have found several companies that will supply already assembled electronics (caps, switches, enclosures, etc,) for reasonable prices, almost as cheap as a static converter. I supply them the spec off my motor and they build the box ready to hookup. Definaty worth considering. Anyways, plenty of good reading on google and I guess I just need to research this subject a little more.

 

[Kyle_in_Tex]

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

Sawyer Rob didn't get a deal, he got a Steal! Good luck finding one that cheap. You need to look up on one of the websites that tell you how big you need.

https://www.americanrotary.com/?gclid=CNvRpemlwMYCFYQ-aQodJOsGpA

 

[muddstopper]

Sawyer Rob didn't get a deal, he got a Steal! Good luck finding one that cheap. You need to look up on one of the websites that tell you how big you need.

https://www.americanrotary.com/?gclid=CNvRpemlwMYCFYQ-aQodJOsGpA

Yea, I thought it sounded a little to good to be true. Rob, you didnt pick that thing up at night did you??JK.

Kyle, I know I can get by with around 7.5hp. The mill is rated for 5hp and according to what I have read, 1.5 time bigger seems to work best. The kicker comes in if I decide to buy something else to pull 3 phase also. As long as i didnt go over 5hp on the new equipment and just ran one thing at a time. I would still be good with a 7.5hp converter. Now being as I know my unreasonable tendencies to either overdo or oversize everything, I would just feel better with around a 10hp converter simply because i would worry less about overloading anything. I think the only downside to getting to big a converter is just in the amount of electricity the converter consumes, but I dont run my equipment enough to run up a huge power bill with the equipment. If there is another down side, I havent read about it yet. With a freebie 25hp 3phase motor just begging me to come and get it, I cant decide just what I should do or how big to go.

 

[AGRIMAN]

I have a 35 HP rotary converter on my PC oven and it's works very good. I gave around $1,500 for it 6 years ago.

 

[muddstopper]

Well, I dot know what a pc oven is supposed to cook, but 35hp is pretty big.

In the past i have not even considered a lot of relativity cheap equipment simply because it was 3 phase. Building or buy a phase converter might just lead to a divorce. I spend enough on ebay already

 

[AGRIMAN]

Well, I dot know what a pc oven is supposed to cook, but 35hp is pretty big.

In the past i have not even considered a lot of relativity cheap equipment simply because it was 3 phase. Building or buy a phase converter might just lead to a divorce. I spend enough on ebay already

Power Coating oven 8'x8'x24. I would not be afraid of using a converter on 3 phase equipment.

 

[LD1]

Agreed that you dont want a static.

Nothing wrong with a rotary, especially if you have a shop full of equipment. Lots of ways to start it. Rope as mentioned, 110v pony motor, or capacitors to start (same way a static starts). And yes you need run capacitors to balance the third leg to better match the two legs that are getting power from your single phase.

VFD's are nice though, and not too terribly expensive unless you splurge for a name brand. Can vary speed nicely. But they are limited purpose. If you have a shop full, RPC is the way to go.

 

[newbury]

<snip>

My $250 reference was if I could buy a complete rotary phase converter for that kind of money, it sort of made building my own seem kind of foolish. Now that I know I probably aint going to find a complete converter for $250, I'm back to trying to figure out how to do it myself, again. One thing to note is I have found several companies that will supply already assembled electronics (caps, switches, enclosures, etc,) for reasonable prices, almost as cheap as a static converter. I supply them the spec off my motor and they build the box ready to hookup. Definaty worth considering. Anyways, plenty of good reading on google and I guess I just need to research this subject a little more.

As I wrote PhaseCraft sells the box for $220 for the 10HP I was looking at. For a 7.5HP it's $190. I just had problems finding the motor for MY price. Since then I've been following the Govt auctions and occasionally see 10 to 20 HP motors pop up, example Public Surplus: Auction #1047890 10hp for $75.

Well, I dot know what a pc oven is supposed to cook, but 35hp is pretty big.

In the past i have not even considered a lot of relativity cheap equipment simply because it was 3 phase. Building or buy a phase converter might just lead to a divorce. I spend enough on ebay already

There is a lot sold from school auctions also, relatively unused because many schools are phasing out industrial arts for computer labs. When I bought my stash in the picture one of the teachers of another area in the same school had been trying to get this bandsaw out of his shop


He just put it out on the trash when he saw I had room in my trailer for it (best dumpster dive I ever did). And virtually all of the stuff I get from the schools has been well maintained and stored well. A lot of DOD auctions they let good equipment set outside

/edit - I can't get into machinist stuff. I've only got about 5,000 sq feet and it's about full already.