Single to Three Phase Help, Please

[elalto]

Hi All,

I have out grown my 9x20 lathe and bought a 14X40 to be able to work on a little heavier stock. Problem is the "new" lathe has a 3 HP, 220 three phase motor and I only have single phase service.

Doing some research, I have managed to totally confuse myself and need some help. Questions: 1. Can I get by with a static converter eventhough I will lose 1/3 of my horsepower? 2. If I go with a rotary converter will I have to buy a full 3HP idler motor? 3. Why are phase inverters sooo expensive??

I appreciate any and all help I can get, and thanks in advance.

Marcos (elalto)

[HuFlungDung]

Hi Marcos,

I would suggest that you investigate the variable frequency drive option, instead of a phase convertor. I don't know how the dollars compare exactly, but you might enjoy the added convenience of a variable speed main motor. See Swede's thread about this type of issue.

[vacpress]

elalto - i have the same VERY frustrating problem. ive got a real nice table saw that i cant use unless i rig some "jankered" rotary convertor, pay big $ for 3-phase wiring, or get anm inverter.

i hate this problem.. i have basically decided to try and put a 120\220v single phase motor in the thing.. or to never use it ever... i maybe should just sell it and buy something i can use...

problem is its worth alot of $$$ to me, not to anyone else... it has a nice fence, etc. suckers

[Ken_Shea]

Hi elalto,
Having in the past been through the static and rotary phase converters thing, can say with out reservation, forget the static, I had even bought high quality units and they were an absolute waste. The Rotary phase has, on the other hand, been flawless, much higher starting torque and gave quieter running motors. A commercially built rotary will be entirely self-contained with nothing but the wiring to hook up. They actually are not all that much more expensive compared to high quality static. I needed one to run a 2 and 3 horse motors, the cost was $1000 USD. All rotary converters are not created equal so do some homework besides looking at only price if you decide to go that route.

Ken

[Swede]

While it is a pain to get three phase into your home shop, once it's there you'll like it. Motors are cheap, powerful, can be reversed VERY fast. I have used a rotary phase converter in the past. I mounted it into the attic and ran conduit down to a 3-phase outlet station. The good news is, with one rotary converter, you can run a shop full of three-phase machines; you don't need to use one converter per machine.

I am currently working on a VFD conversion of my mill, see the "General Electronics" forum for the thread.

Good luck!

[Ken_Shea]

Swede It may be more then a pain to get 3 phase in a home work shop, it may be impossible. Even at my business they wanted a mere $3500 to bring it in, and then of course there was that minium usage fee, inspection fee, and $800 per pole if there was not a set of transformers near by, and they call it a CO-OP electrical company.

How did I miss the VFD conversion thread ?

I'm gone

Ken

[Al_The_Man]

Some time ago I built a 3ph rotary converter for my shop, I think I still have the design information, if there is interest I could dig it out and post it, The one I built used a 7.5 hp 240v 3ph motor.
I picked up a NOS motor locally and the total cost was around $200.00.
Al

[Swede]

Originally posted by Ken_Shea Swede It may be more then a pain to get 3 phase in a home work shop, it may be impossible. Even at my business they wanted a mere $3500 to bring it in, and then of course there was that minium usage fee, inspection fee, and $800 per pole if there was not a set of transformers near by, and they call it a CO-OP electrical company. Ken

Ken I was referring to a rotary phase converter. I didn't even bother my electric company, I knew that it would be ugly, just as you found.

What I am suggesting is a nice installation of a pretty heavy-duty rotary phase converter, which will supply your entire shop with quality 3p power. When I moved into my current home, I was sick of having this big rotary converter humming away in a corner of my shop, so I took a day off and installed it in my attic. I added a 30 amp circuit to my service panel, and routed the juice to the attic phase converter. From there, it went back down to my shop in a nice conduit, and was terminated in a junction box which feeds several 3-phase outlets. A fused, 3phase safety switch energizes/deenergizes the converter from the shop. So that's my 3-phase power station There's still a minor hummmm from the attic with the converter on, but it's not too bad.

[Bloy2004]

Swede..
Now that you are going to use the VFD you are installing, will you be dismantling the rotary phase converter?
Is the advantage of the rotary phase converter that it supplies 3ph to multiple units where a separate VFD is required for each motor used?

[Ken_Shea]

Dang Swede, these suckers are heavy, bet that was no small task getting it up there, did your wife carry it up there for you

Some units are quieter then others, that is one of the issues you have to consider prior to purchasing if it is going to be necessarily close to the work area. The unit here is a Kay Industries and is remarkably quiet.

[Swede]

Originally posted by Bloy2004 Swede.. Now that you are going to use the VFD you are installing, will you be dismantling the rotary phase converter? Is the advantage of the rotary phase converter that it supplies 3ph to multiple units where a separate VFD is required for each motor used?

I'm going to keep the rotary converter going for my Hardinge lathe. Since the Hardinge has a variable sheave arrangement that works fine, I doubt that I'll mess with it.

VFD's can power more than one motor. It wouldn't be hard to have a "selection station" where you'd first select the tool to be powered with a pushbutton which would close a 3-phase contactor, finishing the circuit between the VFD and the tool, then powering up the VFD with another button push. You could have some cool red lamps indicating which machine is "engaged". You don't want to disconnect a motor from a VFD when they are both "alive", hence connect the machine --> VFD first, then power up the VFD.

The only prob I could forsee would be that each tool might have different VFD programming needs, but you could probably work around that.

Ken LOL you must know my wife. She is a fitness monster. She was an All-American volleyball player in college (Olympic caliber, she's awesome), 6'1" tall. Fortunately I'm 6'3". Her sister is 6'5", and her brother is 6'10". A TALL family.

You bet I put her to work. "Hon, I need you to schlepp this 75lb phase converter and install in into the attic rafters!" Hehe, no I don't think so!

Honestly, if I knew it was as noisy as it was, I don't think I would have bought that brand, a "Phase-A-Matic" rotary. It's not like a chain saw, but when it hums and vibrates for hours at a time, it's irritating.

[ESjaavik]

One more point: a VFD is made to drive asynchronous motors, that's it. Hook it up to anything else and it's anybodys guess what will happen.

Reprogramming it when changing to another tool is usually to much of a pain to make it useful. You should ask the salesman if programming it for your biggest motor would work provided you never drive more than one motor. You will then surely not benefit from the motor protection features for your smaller motors, but you don't have that on a rotary either.

For a lathe I would use the VFD. Would'nt it be nice to increase the RPM while doing a facing cut to get a pretty cut all the way in to the center?