# Rotary



## Phils69 (Nov 9, 2012)

Looking to buy a mill and lathe soon. The phase converter in the link below came up near me. Is American Rotary a good brand? 

http://www.americanrotary.com/produ...-phase-converters/10hp-rotary-phase-converter


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## 8ntsane (Nov 9, 2012)

I have heard they are good qaulity, but if your powering only 1or2 machines, a VFD might be more appealing to you. The VFD prices are quite good these days.


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## Phils69 (Nov 10, 2012)

He wants $700 for the rotary. How does that compare to the variable drives and what's a good brand of VFD?


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## DaveD (Nov 10, 2012)

Can't help you on the VFDs but if the used rotary is 10hp then you aren't saving much over the factory price. The 10 HP rotary will start a 5 HP machine with no problem. What are your requirements? Also you have to consider any machine controls that might not go through the VFDs and how to power them. That 10hp rotary is probably going to need a 50a breaker. That's what I run my homemade one on.


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## 8ntsane (Nov 10, 2012)

That price seems pretty high, You could build your own much cheaper Im sure. VFD brands are many. I have a couple of Teco VFDs that I happen to like. Easy to wire up, and easy to setup. Very user friendly.

If its only 1 or 2 machines, look at the VFDs


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## Old Iron (Nov 10, 2012)

I have a 10hp rotary phase converter, I have 6 machines in my new shop and I can run 3 at a time if needed. Only ones I really have to watch what I'm doing is the Lathes and the shaper. 

VDFs are great if you only have 1 or 2 machines, But if your like the rest of us there always following people home.

Every time I get another one I say know more but I always find another one to take home.

That is a high price for that one, I've got nothing in one and about 200.00 in the other. Had to buy all of the components for that one. Both are 10hp.

Paul


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## Phils69 (Nov 10, 2012)

It will be a mill, lathe and surface grinder. I want a cutoff saw too but don't know if they are normaly single phase?


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## 8ntsane (Nov 10, 2012)

Old Iron has a good point about machines following us home. For the guys that have that happen alot, the RPC is better. Ive built several converters for other guys, and usually I had 2 to 3 hundred bucks into the project. Most where 7.5 to 15 hp, and all pony start. No start caps, and never bothered with trying to balance them either.

How many machines do you need power for?
That may be the deciding factor VFD,or RPC.


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## Phils69 (Nov 10, 2012)

It will be 3 machines with a optional saw if they are normally 3 phase. The mill will be at most 3hp but not sure about the lathe and grinder.


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## Cuzzun_itt (Nov 13, 2012)

I have a 10HP & 20HP American rotary and a 50HP that I think is TECO (man its noisy) but they are
 all to run CNC's. If I were using them on a manual machine, I would have just built it myself. However 
I couldn't find an idler that would be balanced well enough for the cnc control.

If you plan to run manual equipment you need to find an idler motor that I would recommend is at least 
1/3 bigger than your highest load. Thats because you are generating one third of the power.

Good Luck!!

Paul


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## Phils69 (Nov 14, 2012)

I'd like to build one with a 7.5hp output. I'm assuming a 15hp 3 phase motor but am confused on what capacitors I will need along with the other stuff.


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## 8ntsane (Nov 14, 2012)

Hi Phil    , Sounds like your thinking of building your own. I would assume that your powering up a 3hp machine if you have chosen a 7.5 hp motor for your RPC. The RPC motor should be atleast 2X the size of the motor its driving min. If you want to keep things simple, I would just pony start the converter. Ilike the pony start because it takes a ton of wiring out of the mix. I also havnt had much luck with the offshore caps being reliable as well. Could be just the source I was purchasing form, not sure. For a pony start, you only need a small 1/4 to 1/2 hp 120 volt motor for the job. You could even wrap a rope around the shaft and pull start it like a old lawn mower. No need to get fancy here. Some guys want the push button start, its a personal choice really.


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## 8ntsane (Nov 14, 2012)

Ok, see your going to power 3-machines. Providing its only one at a time, just use the X2 to base it off. The choice of motor can make a huge difference with noise output. The least amount of noise would be the 1200 rpm motor. The usual is the 1750 rpm motor. The 3600 rpm motor I would not use, those guys are turning a lot of rpm, and with rpm, the noise level goes up with it. For the simple RPC, and pony start, I just round up the following parts. The main motor for the RPC, chosen buy the HP I intend to drive. Also, the lowest RPM as mentioned above. A pony motor of 1/4 hp on up to get the big guy spinning. The main motor and pony will need sheeves, and try to size the them to get you main motor spinning at name plate rpm, they start easyer. So, 2 pulleys, 1- belt, then I allways favor the cuttler hammer 3 phase disconnect box. That is your main basics for parts, other than wire. Most all of this you can dig up in craigslist and such. If you seach for my posts on RPCs , you should find pics of my simple RPCs I posted some time back. I also do not bother with run caps, or any balancing. Machines like lathes/mill are used under variable loads, and different loads will drive you crazy trying to balance them.


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## Phils69 (Nov 14, 2012)

Thanks. Let me do some research and call around to find a motor and ill post back wit the progress.


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## Phils69 (Nov 14, 2012)

Found a local shop that I can get a used 15hp 3 phase motor from for a couple hundred bucks with a warrenty he said. I've had no luck with any local scrap yards or Craigslist. Here is what I think I will need. Correct me if I'm wrong

Main motor. 15hp 3 phase
pony motor 1/2g hp?
square d 3 phase disconnect box
3 phase wire to hook up each machine. Can 3 machines be hooked up to the square d box or will I need a seperated box with multiple outlets that I can put a plug on each machine and plug into this box? Also what size wire should I buy?


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## Cal Haines (Nov 14, 2012)

Phils69 said:


> Found a local shop that I can get a used 15hp 3 phase motor from for a couple hundred bucks with a warrenty he said. I've had no luck with any local scrap yards or Craigslist. Here is what I think I will need. Correct me if I'm wrong
> 
> Main motor. 15hp 3 phase
> pony motor 1/2g hp?
> ...




I'm a little late to the party here, but I wanted to add a few things.

Even if Phil didn't have other machines to run, a VFD would not make sense here.  This machine already has a variable speed drive.  It uses a motor/generator (MG) to provide DC to the spindle motor, so the variable part of the VFD provides no benefit.  The MG wants 220 3-phase, not the 180 VAC that most VFDs put out.  A VFD that can provide 220 3-phase at the current level that this machine requires is pretty expensive.  I don't know of anyone running a 10EE MG machine from a VFD.  Some folks, mostly guys that didn't understand or appreciate what they had, have torn out the MG and DC spindle motor and cobbled in an AC motor and VFD, but it does not deliver the performance of the original drive.

Phil,

I use a 7.5HP idler motor with my MG 10EE and it works just fine.  I would not go the pony motor route.  All you need to start the idler motor is a simple potential relay and a pair of capacitors.  If you're comfortable doing house and shop wiring, it will be easy enough for you to build.  A pair of run capacitors are a good idea to add to the converter to balance the current on the artificial third phase.

You should be able to pick up a used 7.5HP 3-phase motor to use as the idler motor for under $100.  The rest of the parts for the converter are probably under $50 and you can build it in an afternoon.

My converter is on a 30A circuit.  I'm sure it's not to code, but I have all of my 4 machines hard wired to the converter.  I use ¾” EMT and 4x4 boxes to get power to the wall behind the machine, then flex conduit to the machine.  You can use outlets and cords if you like.  Add as many outlets as you like.

(Assuming a 7.5HP idler motor) use at least #10 wire; #8 for long runs.  Locate the converter near the circuit panel if possible.  All the wiring to the machines, including the cords should be at least #10.  Each machine should have fuses size to the particular machine's wiring.  Note:  the circuit breaker and the fuses are there to protect the wiring, not the machine; overload devices on the machine are used to protect its motor(s) from overload.

Do yourself a favor and run 5 wires to each plug (or box if you're hard wiring): 3 black (or red, black, blue), green/bare safety ground and white common wire.  Adding the white wire allows you to put a 120 work light at the machine, if desired. (Also, if your 10EE’s exciter fails, having 120 at the machine will be very helpful for reasons I won’t discuss here).  I prefer metal conduit (EMT) and stranded wire.  Don't put Romex cable in a conduit, get individual wires and pull them as a bundle.

If you have a recycling place near you, see if you can buy the wire from them instead of paying full fare; these guys are going to sell their wire to China by the pound (and they get less per pound because it's insulated), so will often sell to you for a small mark up over what they get for it.  Just make sure you know what new wire costs per foot before you go in.  You pay through the nose for wire at Home Depot or Lowes.  Electrical supply companies are cheaper.  If you have a contractor buddy, see if he will buy wire for you on his discount.

Most of the noise from an RPC is the idler motor's fan, which is usually pretty primitive.  Since the idler motor isn't running at its name plate power, it doesn't need as much cooling.  I took the fan off my idler motor and it's very quiet.  I keep track of its temperature and if I'm going to be running it for a long time I put a floor fan on it so that the case never gets too warm to touch.  A lot of motors are spec'd for a 50 degree C rise (90 F), so they can run a lot hotter than mine ever gets.

I wouldn't be particular about the brand of 3-phase disconnect.  Get one that's rated for at least the HP size of your idler motor.

_Cal_


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## DaveD (Nov 15, 2012)

Do you have enough power to run that 15hp motor? I don't thing a 50a breaker/wire will do it. Going larger starts to get expensive fast.


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## Phils69 (Nov 16, 2012)

Good point Dave. I'm in a garage with normal service. Would that do for a 7 1/2 hp idler motor?


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## Cal Haines (Nov 17, 2012)

Phils69 said:


> Good point Dave. I'm in a garage with normal service. Would that do for a 7 1/2 hp idler motor?


You need 30A @ 240 for a 7-1/2 RPC.

How far away is the breaker panel for your shop?

_Cal_


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## Cheeseking (Nov 17, 2012)

Phils69 said:


> Good point Dave. I'm in a garage with normal service. Would that do for a 7 1/2 hp idler motor?



Normal as in 120V/15A/1P ?  If you plan to set up shop probably wise to run a 50-100A  sub panel up to the garage and go from there.


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## Phils69 (Nov 18, 2012)

The breaker panel is in the garage where the machines are. I'm renting this place so I just want to pull a 220v line on a 30amp breaker. Looking to buy a home at the beach next year then I will set up shop for the long haul. Just want to build one now that I can carry to the next place.


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## Cheeseking (Nov 18, 2012)

7-1/2 hp rotary will pull 35-40A maybe more starting so check rating plate.   I always upsize 120%  Then next std size.
You may want to  consider 60A dedicated to the rpc IMO 

220v 60A fused disconnect to a mag starter w/overloads protecting the converter and a 3P 20 or 30A fused disconnect on the output to protect  conductors feeding all your twist lock outlets.  

Then manual starters/w overloads at each machine.  

Lots of switchgear in a small space but if ya wanna do it right......


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## flutedchamber (Dec 22, 2012)

I have a 20 hp Rotary phase converter.  I use a 60 amp square D QO breaker and upsized the feed wire 150%.  It draws 125 amps for perhaps a second before settling down.  No breaker problem or problem with the unit in three years.  Rotary recommends the correct size breaker and wire in the info that comes with the converter.  They are also a great source of 3 phase Square D QO breakers and breaker panels.


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