RE: Converting 3 phase to 1 phase

[Todd Cioffi]

Hi,

What's the easiest (and most inexpensive) way to convert a power tool from 3 phase to 1 phase so that I can run it in the basement of my home?

Thanks,

Todd

[gjat]

I'm not a real electrician, but if memory serves me right, you would need a pair of buck/boost transformers to change the 120/240v single phase to 3 phase. It's better to just replace the motor.

[Daryl]

There are electronic converters that give a three phase boost at start up and then cut out. Depending on the load you can burn the motor up using them. I would suggest you keep your eye open for a rotary converter.

[scorrpio]

The 3-phase tools are 3-phase for a reason. You can change to a single-phase motor, but in order to end up with a tool of equivalent power, it'll have to be one huge motor.

[LarryG]

Well, certainly the easiest way,and in the long run perhaps the least expensive too, would be to replace the three-phase motor with a single-phase motor of the same horsepower rating. I don't know a whole lot about phase converters but I do know that there are some half-azzed designs that are cheap but don't allow the motor to develop its full rated power and may not be entirely safe; and well-engineered models that don't compromise on power or safety but cost a whole lot more. I'm not sure investing in a good phase converter would make economic sense unless maybe you'd bought a whole shopful of used tools with three-phase motors.

A potential problem with changing the motor is that a single-phase motor of the same HP rating as the three-phase might be pretty spendy. A possible dodge here is to fit a smaller motor. Three-phase motors are typically used in commercial or industrial applications needing lots of horsepower and/or involving continuous duty. What kind of tool is it? If it's something like a 5HP cabinet saw, the average hobbyist woodworker could hang a much less expensive 3HP motor in the thing and would never know the difference.

[Todd Cioffi]

RE: Three Phas to One Phase for a Lathe

I may be able to get a true shop lathe for dirt cheap, but it's three phase. Given that it's a lathe, I may be able to run a cheaper rotary converter on it. Any thoughts?

Todd

[vaking]

3 phase motors are usually installed where there is a need for more power than 1 phase can comfortably deliver. Replacing 3-phase motor with 1-phase of a same output will be difficult - the motor itself will be expensive and the wiring in your shop may get in trouble since you may be asking for more amps than wires and brakers can handle. Converters exist but you will still have the same issue of not having enough amps in your shop to get full output. In other words - by installing this lathe on a 1-phase circuit you will loose the power compared to what it was designed. 1-phase circuit in most cases uses 15 Amps and can handle up to about 2HP motor (some routers and shop vacs claim more but they are lying). You can have a 20Amp circuit but it will require special outlets and plugs. Check the faceplate of that lathe - if that 3-phase motor is more than 3HP - I would scrape the whole idea.

[JSCOOK]

Why not try a "Home Made 3-Phase" set up .... see link:

http://www.team.net/www/shop-talk/hm3phase.html

[LarryG]

I may be able to get a true shop lathe for dirt cheap, but it's three phase. Given that it's a lathe, I may be able to run a cheaper rotary converter on it. Any thoughts?

I thought rotary converters were the more expensive type??? Or maybe you literally mean one of the cheaper rotary converters, as opposed to one of the expensive rotary converters. As I said, I don't know a lot about the things.

Again, I'd suggest checking the motor size and pricing a single-phase motor of the same HP rating. I just spot-checked the specs of a few lathes (Powermatic, JET, Oneway), and you have to get into some real whopper metalworking lathes before the motor gets above 3HP. As electric motors go, that's not that big (although it will require 240V, but then so will a converter).

[Thom2]

Depending on the size of the motor, I'd probably look into a VFD (Variable Frequency Drive). These units are available with 220v single phase input and 208/220v 3 phase output. Most units will also offer the convenience of variable speed, which depending on the application (like a Lathe) is a HUGE plus.

I currently have (2) units on hand with a 1hp 3phase motor that I plan to experiment with to make my BS full Variable Speed. Fortunately for me I got these units for free because I know people that work maintenance in an industrial environment and they see these things hitting the dumpster when it comes time to upgrade to DC controllers/motors.

A (very) quick search yielded something like this tho:

http://web1.automationdirect.com/adc...trol)/GS1-21P0

You'd have to do your own research on that unit, but for $125 it's definately "reasonable" as a 1hp single phase decent quality (non-HF) motor will probably set you back almost $200 (new).

Do your homework tho', there's several different ways to go about what your trying to do, only you can decide what's going to work for your situation.

HTH