# Rotary Phase Converter Question for Newbie



## bnelson1980 (Feb 22, 2018)

I've order the parts to complete my Sharp LMV 50 Mill. The 3HP 3 Phase motor arrives next week. I called American Rotary to order a Rotary Phase Converter. I almost pulled the trigger, but wanted to check with you all to get your advice and make sure I am not going overboard with what American Rotary is saying I need. 

They said that because it's a 3HP 3 Phase Mill I would need there 7.5HP AD Rotary Phase Converter. I also need the 3 phase breaker which is $99 and a couple other plugs and receptacles. Comes out to almost $1,200 for the Rotary Phase Converter setup. Seems kind of high to me? If that is what I need, then I will buy it. I just want to make sure I am not being taken advantage of. 

Thanks!


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## Ed ke6bnl (Feb 22, 2018)

American rotary is a good honest company, and he is correct about needed a larger 3 phase motor than 3 hp you are going to run. I am not electronic guy but I made my own set up 15 years ago with capacitor and relays I used in the Air Cond. job. but for the last one I just hooked up a static  phase converter for about $100 and put that on my my 5hp motor I already had for my 3 phase Bridgeport mill. BUT you are dealing with the right place to buy everything with quality and knowledge of the subject.


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## MikeInOr (Feb 22, 2018)

I usually select an ideler motor at 150% of the largest motor I am going to start... which it seems like a RPC with a 5hp should be suffient.  Nothing wrong with stepping up to a 7.5 though.

I usually ebay surplus contactors, breakers, plugs, recepticals, etc. Which usually saves a lot of money.  If you are not comfortable with hunting down your own components $99 retail on a breaker does not sound outrageous to me.

Personally I prefer VFD's if the machine only has 1 x 3ph motor.


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## benmychree (Feb 22, 2018)

Sounds like overkill to me; there is no significant starting load with a machine like that and you will likely never use the 3 HP;  I'd look at a 5 HP unit.  I too made my own phase converter with a motor not significantly larger than my biggest machine motor, used a static converter to start it and oil filled capacitors to balance the phases.


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## mksj (Feb 22, 2018)

You might also consider a VFD, the Teco L510-203-H1 is $200, the Hitachi WJ200-022SF is $320 and you could simply wire it for 2 wire control or 3 wire control. As far as RPC's a 5Hp should be able to start/run a (unloaded) 3 Hp motor, it is not a big load, American Rotary says 2.5Hp for their 5Hp.  Other RPC manufactures state a 5Hp RPC (PL-5) can starts a 3Hp light to medium load motor.   The 7.5 Hp RPC below is $630. You could also purchase a control panel and get a good motor for less.

http://dealerselectric.com/L510-203-H1-N.asp
http://www.northamericaphaseconverters.com/
http://www.northamericaphaseconverters.com/shop/category/pro-line-rotary-phase-converters/
https://www.ebay.com/itm/American-R...1-3-Three-PH-Heavy-Duty-CNC-USA-/370755610715


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## cathead (Feb 22, 2018)

Rotary phase converters are easy to build up so that is what I did. Used three phase motors are easy to come by quite cheaply.  
I spent maybe fifty dollars on the RPC setup and the money I saved went for tooling.  It's all in how you want to play the game
in this hobby I guess.


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## bnelson1980 (Feb 22, 2018)

They have 3 different series. The one on ebay for $630 is the most basic series which is the AR-Pro Series. American Rotary says I need the AD Digital Smart Series. I would like to know if I really need that AD -Digital Smart Series or if I could just buy the AR-Pro Series 7.5HP for $634?


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## MikeInOr (Feb 22, 2018)

I do not believe your Sharp mill is a CNC machine... I see no reason that you would need the "Digital Smart" series RPC.

Are you familiar with VFD's (Variable Frequency Drives)?  Is there a reason you do not want to use a VFD?  Does your mill have power feeds on the table that are 3ph?


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## cmantunes (Feb 22, 2018)

mksj said:


> You might also consider a VFD



I second mksj suggestion. There are plenty of 230V single phase VFDs out there able to handle 3HP motors. I don't see the need for a rotary phase converter.


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## cg285 (Feb 22, 2018)

although i think a 5hp should be just fine i would still go with 7.5. never know what the future brings and there probably is not much difference  in price. my 7.5 runs all my machines but one. and up to 5hp

building one is much cheaper if you feel comfortable doing that. i built a 20hp for around $500. i was lucking finding the motor tho'


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## bnelson1980 (Feb 22, 2018)

I just got off the phone with Dave Kwasny from North American Phase Converter. He spent 20 minutes with me on the phone talking about phase converters and different options. We also discussed building one and just buying the control panel from them. Very informative. I will be buying from North American Phase Converter instead. 

Also, I'm not opposed to using a VFD, my problem is I really don't know much about them. I've heard that you have to be good at programming too? I am going to look into them as well to learn more.


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## projectnut (Feb 22, 2018)

bnelson1980 said:


> I've order the parts to complete my Sharp LMV 50 Mill. The 3HP 3 Phase motor arrives next week. I called American Rotary to order a Rotary Phase Converter. I almost pulled the trigger, but wanted to check with you all to get your advice and make sure I am not going overboard with what American Rotary is saying I need.
> 
> They said that because it's a 3HP 3 Phase Mill I would need there 7.5HP AD Rotary Phase Converter. I also need the 3 phase breaker which is $99 and a couple other plugs and receptacles. Comes out to almost $1,200 for the Rotary Phase Converter setup. Seems kind of high to me? If that is what I need, then I will buy it. I just want to make sure I am not being taken advantage of.
> 
> Thanks!



I think they're quoting you a price for a top of the line system.  In a perfect world where money is of no concern it would be the "best" way to go.  However since money can be a concern I think you can get by with a much less expensive system.  Personally I would consider a static converter (at least as a temporary solution) if finances won't allow you to purchase a rotary one.

I have 3 machines in the shop powered by static phase converters. A 1.5 hp Bridgeport mill, a 1.5 hp Racine power hacksaw, and a 2 hp Sheldon lathe.  They are all using 1-3 hp static converters.  The mill has an older Phase a Matic, and the saw and lathe have American Rotary's.  The mill has been running on the Phase a Matic for about 15 years.  The other two machines have been on the American Rotary converters for a couple years

My intention is to in time convert the entire shop to a 15 hp American Rotary brand rotary phase converter.  I have all the hardware in stock, but need to get another sub panel installed before hooking up the system.

A 1-5 hp American Rotary static converter costs less than $200.00.
https://www.wolfautomation.com/inde...MI4OrMgL-62QIVQbnACh3gKwKTEAAYASAAEgJvu_D_BwE

The only disadvantage is that the machines will run at about 2/3 the rated hp.  The system only generates the third phase (using capacitors) for a few seconds during startup. Once the machine is running it's essentially on single phase.  I have never had a situation with any of these machines where running below the rated hp was a problem.  I have worked all of them hard for as many as 10 hours at a time with no problems.

American Rotary has made over 3400 sales from their eBay store.  The only complaint I found was someone who was unhappy that they needed to pay the transportation company an extra $50.00 to have a unit delivered by a truck with a lift gate.  Personally I can't believe eBay allowed a comment that should have been directed to the trucking company to  influence the rating of a seller.


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## mksj (Feb 22, 2018)

Nothing special about the LMV-50 that you need a CNC rated RPC, it is considered and easy start load. Typically for CNC you need a RPC 2X the rated Hp of the load and better leg to  leg voltage control. I have a LCM-42 (LMV-42) so I am familiar with the mills, I purchased mine with the digital head and VFD,  the control system is extensively modified. The base mill is about as basic (i.e. no circuity or semiconductors) as you can get, so any RPC would work. I agree, that a 7.5 Hp RPC might be a better choice only if you think you will be running more than one machine or might have equipment down the line that would need a larger RPC. My friend had a Phase-Craft RPC control system with a custom 7.5Hp idler motor, he routinely starts 5Hp motors with ease. You also need to consider your available 240VAC service for the size RPC you are using, not sure but probably need a 50-60A breaker for 7.5Hp, 30-40A for 5Hp.  RPC's can also be a bit noisier, seems to be a wide variation so something to check. Better quality units use a 1750 RPM idler motor should be quieter, but something to factor in the decision process.

The Teco L-510 is very simple and easy to program, I can put together a parameter file if you have the motor nameplate info and how you want to control the VFD inputs. I recommend 3 wire control, pick up a few switches from Automation Direct and put them in a small box. I recommend 3 wire control which uses a momentary push button for stop, a momentary push button for start, and a sustained switch for forward/reverse. Download the manual, 99% of the parameters are not touched. The motor is directly wired to the VFD, no switches. At $200, I recommend it over the other options if you only need 3 phase for one machine. You also get soft start, braking and variable speed. VFDs go not play nice with GFI's so if you have one, then go with a 5Hp RPC if just running the LMV-50.


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## dennys502 (Feb 22, 2018)

I started out with an American Rotary AR5  but had to upgrade for my lathe which is 5hp. I went to a AD10 with the intention of adding a 5hp cnc mill.
Now my air compressor is getting tired and parts are no longer available to rebuild the compressor. It is not quite large enough for sandblasting large items so I'm planning on going to a 7.5 hp 3 phase compressor. 
Which presents another problem requiring me to upgrade my RPC again. 
It's hard to see into the future but if you plan to add more equipment it would be a lot cheaper in the long run to get a larger power source at the beginning. 
Think about equipment you might add and look at the largest hp required and adjust accordingly. 
I like to have the capability of running 2 machines when possible.


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## agfrvf (Feb 22, 2018)

Go VFD. You get simple, cheap, quiet and small footprint as well as speed control. RPC's are old tech.


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## SSage (Feb 23, 2018)

I'm running the cheap unbranded 3ph converters/VFD's out of China. Ebay has them occasionally, mine have lasted for years. I don't think mine are still sold, but they are cheap enough to put one on each 3ph machine. Even the little $100 1.5 kw 220 volt converter has lasted over 6 years now. I figured out the chinglish manuals, it makes sense after a few beers. They are cheap enough to keep a spare, but I haven't had one fail yet.


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## Eli (Oct 14, 2021)

I built my 10 hp rotary and my balance as it stands now is AB 236  AC 238  BC 142 . My question is if that looks good to go even though I can probably do better but is that ok to go . Any one with experience on this subject of balance?


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## Eli (Oct 14, 2021)

Eli said:


> I built my 10 hp rotary and my balance as it stands now is AB 236  AC 238  BC 142 . My question is if that looks good to go even though I can probably do better but is that ok to go . Any one with experience on this subject of balance?


Sorry last one is 242 not 142


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## MikeInOr (Oct 14, 2021)

I have been starting a 7.5hp Redstar Radial Arm Saw with a home built balanced RPC using a 10hp idler motor for 20+ years.  Yes, a RAS has a very low starting load.

AB 236 AC 238 BC 242 - Is very well balanced!  Much better than most RPC's that I have come across.  My balanced RPC has a variance of about 15v across the different legs and I consider it very well balanced too.

I HIGHLY recommend installing one of these 3 phase panel meters in any RPC.  https://www.amazon.com/Three-Phase-...3+phase+panel+voltmeter&qid=1634267355&sr=8-2


I doesn't give you any information that you really need to worry about when you are running your 3 phase machines...  *BUT THEY LOOK REALLY IMPRESIVE *for about $35*!*


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## Eli (Oct 15, 2021)

MikeInOr said:


> I have been starting a 7.5hp Redstar Radial Arm Saw with a home built balanced RPC using a 10hp idler motor for 20+ years.  Yes, a RAS has a very low starting load.
> 
> AB 236 AC 238 BC 242 - Is very well balanced!  Much better than most RPC's that I have come across.  My balanced RPC has a variance of about 15v across the different legs and I consider it very well balanced too.
> 
> ...


Lol thank you so much I’m sure going to get one for visuals sake . Like you said it sure looks good.


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## Eddyde (Oct 16, 2021)

I built my 7.5hp RPC to run my 5hp lathe (here) and have similar balance under load. I think AB 236 AC 238 BC 242 is excellent.


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## Groove (Thursday at 11:32 AM)

I know this is an older thread but my question seems appropriate for this thread. 
question: I would like to build a RPC and I was wondering if I need a special type of 3 phase motor to use as my power source Idler motor? Or if I can buy any 3 phase motor for my idler?


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## rabler (Thursday at 11:41 AM)

Groove said:


> I know this is an older thread but my question seems appropriate for this thread.
> question: I would like to build a RPC and I was wondering if I need a special type of 3 phase motor to use as my power source Idler motor? Or if I can buy any 3 phase motor for my idler?


Pretty much any standard 3 phase induction motor will work.  (Obviously you want one that can be wired to your desired voltage, typically 230VAC).  Generally folks prefer the lower rpm motors as they are usually a bit quieter.  Typically a used (i.e., ebay, etc) motor makes a good candidate, as the idler motor doesn't see a lot of torque it isn't going to stress the bearings like actual drive use.


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## benmychree (Thursday at 12:08 PM)

I used a 7 1/2 HP 1750 RPM 230 V motor for the one that I built, and used a static phase converter to start it, and added oil filled capacitors to   (ar least attempt to balance the manufactured leg, noisy, but it works.


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## Groove (Thursday at 12:20 PM)

rabler said:


> Pretty much any standard 3 phase induction motor will work.


So not being an electrical guy understanding the terms, I am not sure if an "induction motor" is different than any other off the shelf 3 phase motor. Thanks for the reply Rabler


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## Groove (Thursday at 1:03 PM)

Never mind Rabler: I found this in Wikipedia: An *induction motor*  or *asynchronous motor* is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.
 - Im not used to electric motors generating power (to create the third leg) as they usually drain power but again my Electrical Knowledge is not worth talking about.


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## Eddyde (Thursday at 2:31 PM)

Yeah, pretty much any 3 phase motor will be an induction motor and work for a RPC. There may be some brushed 3 phase motors out there but I've never heard of or seen one. The good news is used 3 phase motors are usually pretty cheap as commercial and industrial users are just going to buy new. I paid $100 for a used 7.5 hp in great condition off of FB Marketplace.

Here is a link to my RPC build:








						Rotary Phase Converter Rebuild / Build
					

Hi all, I just hooked up a used, Snyder brand, Rotary Phase Converter to my newly acquired lathe (more on that soon). It works but makes excessive noise & vibration, especially when running under no load condition. It sounds like its vibrating at 60hz so my thought is its electrical in nature...




					www.hobby-machinist.com
				




Please feel free to reach out to me if you have any questions.


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