# Running on a rotary phase converter



## SteveStash (Apr 17, 2021)

Anyone running any of their 3 phase PM equipment on a rotary phase converter? I'm looking to get a 3ph 1236T and running it on my 3hp rpc until I convert to a vfd.


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## Aukai (Apr 17, 2021)

My 1340 is temporarily running on a 5hp RPC.


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## Martin W (Apr 17, 2021)

I was running both a 10 hp and 15 hp  RPC until lately, when I brought 3 phase power in. Ran Phase converters for at least 15 years and no issues, other than 1 bad bearing and 1 switch on the converter end. No issues with any machines. These were used  5 days a week at least 8 hours a day.

I had one machine that I had to install a heavier magnetic starter. It would trip before the machine started.

I have also found that since I upgraded to 3 phase power, machines start almost instantly. With the phase converter it would take an extra second or two to get up to full speed. But it never caused any issues. I guess I was just used to the way they ran .

Cheers
Martin


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## tjb (Apr 17, 2021)

I've been using an American Rotary phase converter for several years with no issues at all.  Before purchasing, I contacted American Rotary; they advised a unit that had double the horsepower of the largest piece of equipment in the shop.  At the time, it was a 4hp lathe, so I rounded up and got a 10hp RPC.  Glad I did, because now, I have a 5hp lathe.

I've never had any issues with mine, but based on the manufacturer's advice, you may be pushing a 3hp RPC a little too hard with a 3hp piece of equipment.  I think I'd contact the RPC manufacturer for their advice.

Regards,
Terry


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## Karl_T (Apr 17, 2021)

I do not know PM equipment very well.

if it has any 120 VAC on it, BE SURE its not using the wild leg.  I learned this the HARD WAY. Blew the 120 power feed on my bridgeport years ago.


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## tjb (Apr 17, 2021)

tjb said:


> I've been using an American Rotary phase converter for several years with no issues at all.  Before purchasing, I contacted American Rotary; they advised a unit that had double the horsepower of the largest piece of equipment in the shop.  At the time, it was a 4hp lathe, so I rounded up and got a 10hp RPC.  Glad I did, because now, I have a 5hp lathe.
> 
> I've never had any issues with mine, but based on the manufacturer's advice, you may be pushing a 3hp RPC a little too hard with a 3hp piece of equipment.  I think I'd contact the RPC manufacturer for their advice.
> 
> ...


Just re-read your post.  It reads 3 *ph* 1236T; not 3 *hp* 1236T.  (Read that wrong.  Sorry.)  From the specs for that machine on ebay, the motor is a 1.5 *hp*.  Based on American Rotary's standard, you should be fine with your phase converter.

Regards,
Terry


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## Ulma Doctor (Apr 17, 2021)

a 3hp RPC would be sufficient for running a 1.5hp motor


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## pontiac428 (Apr 17, 2021)

Not much cost difference between smaller units, so spring for the 5hp. I run my 2.5 hp mill and big drill press off mine, and the rotary is completely transparent to operation. I just wish I would have gone larger when I did it, now I want a bigger lathe, so I'll need a bigger RPC.


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## tjb (Apr 17, 2021)

While we're on the subject of RPC's, I have a question for some of our seasoned veterans.  Can more than one piece of equipment run on a single RPC at the same time?  For example, if I have a 3hp mill and a 2hp 6" sander could both be run simultaneously by different operators on the same 10hp RPC?  Just wondering.

Regards,
Terry


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## JimDawson (Apr 17, 2021)

tjb said:


> While we're on the subject of RPC's, I have a question for some of our seasoned veterans. Can more than one piece of equipment run on a single RPC at the same time? For example, if I have a 3hp mill and a 2hp 6" sander could both be run simultaneously by different operators on the same 10hp RPC? Just wondering.
> 
> Regards,
> Terry



Yes.  Each motor you add to the system increases the starting capacity of the system.


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## SteveStash (Apr 19, 2021)

Thanks for all your responses.  Now I just need to get the nerve to hit the "complete checkout" button on the lathe.


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## erikmannie (Apr 19, 2021)

I have an American Rotary AMP-10 for my 3 phase, 220V, 5 HP PM-1660TL. It is perfect. I will not switch to a VFD.

Make sure you get a big enough circuit breaker on your new RPC. I needed 30A for the machine above. The highest speed (1800 RPM) would trip a 20A circuit breaker. I put in a 30A (easy job AND American Rotary was very helpful with this task) and that was fine.

American Rotary has good customer service.


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## erikmannie (Apr 19, 2021)

tjb said:


> While we're on the subject of RPC's, I have a question for some of our seasoned veterans.  Can more than one piece of equipment run on a single RPC at the same time?  For example, if I have a 3hp mill and a 2hp 6" sander could both be run simultaneously by different operators on the same 10hp RPC?  Just wondering.
> 
> Regards,
> Terry



I wonder if this could trip a circuit breaker, either on the RPC or on the main breaker panel (on the side of the house).


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## Janderso (Apr 19, 2021)

I have a 10hp American Rotary. My lathe is 7.5hp. The mill is 3hp.
I never run more than one machine at a time.
American Rotary suggested a 15hp RPC.
My lathe motor is running before I engage the clutch.
Ulma Doc and others said I would be fine with a 10hp RPC.
I saved over $600 and the 10hp is flawless after 2 years. It runs several hours a week.


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## tjb (Apr 19, 2021)

erikmannie said:


> American Rotary has good customer service.


Totally agree.


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## erikmannie (Apr 20, 2021)

I found these notes on my phone for how I wired up my 30A plug and receptacle.


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## erikmannie (Apr 21, 2021)

American Rotary sold me 5-6’ of an SO cable, and at another point I bought the same from Home Depot. Each wire was 8-10 AWG (I don’t remember).

In both SO cables, the wires were green, black, red and blue. Of course, you’re going to use green for ground. It also makes sense to use red and black for the T1 (X) and T2 (Y). 

If you get the X and Y wrong, the motor will run backwards. I don’t know what that would mean for your bandsaw, but it doesn’t cause any problems with a lathe. I did it wrong the first time, and after I saw the result I just switched the two and now everything is the way I want it to be.


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## pontiac428 (Apr 21, 2021)

I had a surprise wiring up mine.  I didn't think the generic schematic in the manual was useful, since I have the heavy version of my mill and the manual covered the range.  There are a lot of electrics in my mill's panel enclosure, but no elec-tron-ics at all.  I just traced out the wires to ensure I wasn't hooking up the wild leg to the 110v accessories, not that it should matter for a lamp, fluid pump, or power feed.  Anyway, I knew I'd be 50/50 on getting the rotation right.  I fired it up, and it turned the right way.  Then I tested my drill press, which ran in reverse.  Well, it was easier to swap the wires in my RPC panel, so I did, and the drill ran correctly... and so did the mill.  Apparently the forward/reverse start circuit is indifferent to leg phasing.  I did not expect that!


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## ErichKeane (Apr 21, 2021)

Janderso said:


> I have a 10hp American Rotary. My lathe is 7.5hp. The mill is 3hp.
> I never run more than one machine at a time.
> American Rotary suggested a 15hp RPC.
> My lathe motor is running before I engage the clutch.
> ...


The big limiting factor seems to be either 'peak torque' and 'startup torque'.  Something like a lathe with a clutch is going to have very little start-up-torque, and you'll likely have a hard time using 7.5 hp worth of power in a lathe.

My 10 hp motor on my shaper however runs a hydraulic pump.  My 20 HP RPC will sometimes 'stall out' and not be able to start the shaper if the hydraulic pressure in the system is too high.  It is close enough that on a 'cold start' if I try to run my power-feed (a 1/2hp motor) while starting it up, that it stalls pretty reliably.


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## 682bear (Apr 21, 2021)

ErichKeane said:


> The big limiting factor seems to be either 'peak torque' and 'startup torque'.  Something like a lathe with a clutch is going to have very little start-up-torque, and you'll likely have a hard time using 7.5 hp worth of power in a lathe.
> 
> My 10 hp motor on my shaper however runs a hydraulic pump.  My 20 HP RPC will sometimes 'stall out' and not be able to start the shaper if the hydraulic pressure in the system is too high.  It is close enough that on a 'cold start' if I try to run my power-feed (a 1/2hp motor) while starting it up, that it stalls pretty reliably.



I had the same issue with running my 3hp horizontal mill on a 5hp RPC... The motor on the mill drives a hydraulic pump. On startup, it would really pull the RPC idler down for a few seconds. After the mill reached its running speed, the RPC powered it fine. I upgraded to a 7.5hp RPC... it doesn't have any problems starting the mill.

-Bear


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## ErichKeane (Apr 21, 2021)

682bear said:


> I had the same issue with running my 3hp horizontal mill on a 5hp RPC... The motor on the mill drives a hydraulic pump. On startup, it would really pull the RPC idler down for a few seconds. After the mill reached its running speed, the RPC powered it fine. I upgraded to a 7.5hp RPC... it doesn't have any problems starting the mill.
> 
> -Bear


Yeah, sadly a 25hp RPC gets super expensive all at once!  I can fortunately just wait a few minutes for the pressure to bleed off (or leave the pump on when I know I'm going to use it in a few minutes), and can avoid having the power-feed on until it is spinning up.  That said, it is clear the 20 HP motor is 'the limit' for my machine.


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## mksj (Apr 22, 2021)

Unless you have other machines you plan to use the RPC for, it is a significant expense for a short term solution. You can  put together a VFD enclosure with a VFD and wire it up with the basic 1340GT install VFD directions for a less than an store bought RPC. Should just take a few hours. I am not a big fan of static converters on lathes, but if you just need something to run the lathe for a short period of time they are much less expensive, or buy a prebuilt RPC control box and find an idler locally. Ratings on RPC's vary by manufacturer, so always important to match up the recommended RPC to the motor load and probably go one size up if you are planning other three phase machines.

My understanding is the 1236T and 1340GT have the same motor, on my 1340GT it was a 2 Hp, so would recommend going with a 5 Hp idler so something like the PL-5, AR-5, GP5NL etc. You also need to factor in what amperage circuit you have available, a 2 Hp VFD will run fine off of a 20A breaker, and a 5 HP RPC probably 20-30A. I would also look for a 1750 RPM idler and a TEFC or better yet TENV for the lower noise.


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## SteveStash (Apr 23, 2021)

I guess I need to zero in on my dilemma.  I knew this would turn into a RPC discussion and I am ok with that. I enjoy hearing about everyone's setups and advice.   But what I would really like to know is: are the advantages of 3PH really worth it?  It looks like even the cheapest conversion  route is going to be around $600.  I can run a 1236T on my 3horse rpc but it will not be handy. It is a plug in setup I built for a few machines I don't use very often.  So, those of you who have made the conversion, what is it that you just couldn't live without now that you have it.  And vice versa, Anyone have a 1ph and wish they had a 3ph?


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## Aukai (Apr 23, 2021)

The machine does not know what the phase power is, I'm on a RPC as I stated, and I went that route for now(VFD ordered) due to the advanced knowledge here supported that route, and there are advantages to that. You will have to dig for the posts for the pros, and cons of each. Maybe someone can refresh some of that information here. If all you want is the machine to work, and the project is not too picky, they will both hit the numbers, there may be finish differences etc., but you can still turn material. You have a great foundation, in the long run after owning the machine you can change over to 3ph, and VFD, it all depends on what your initial needs are.


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## Ulma Doctor (Apr 23, 2021)

a static converter can be made for around $80


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