I'm toying with the idea of buying a big old US-manufactured jointer in the range of 12"-16". It seems all these machines are 3-phase. What do I need to know about the machines in order to determine whether they can be made to run on the single-phase 240V, 20A circuits in my garage?

Also, I've seen people mention rewiring or replacing the motor or using a phase converter to run old industrial-size machinery in a home shop, but what's involved with each of those solutions?

  • 1
    You may get a better response on DIY.SE about getting the 3 phase 240V into your shop. Most likely it'll involve upgrading your home connection by the supplier to a 3 phase and running the wires from the panel to the shop. – ratchet freak Apr 25 '15 at 20:47
  • @ratchetfreak I updated the title to further clarify, but I'm not asking how to upgrade the wiring in my shop. I'm asking if it's possible to make the tool run on the existing 240V, 20A circuit, and if so, how and what limitations I need to be aware of. – rob Apr 25 '15 at 23:26
  • I'm not sure what you mean by the first paragraph ... you mean how to tell if it's a 3 phase motor? – Daniel B. Apr 26 '15 at 1:13
  • @DanielB. not exactly...for example if I can get a 3-phase machine to run on my existing circuit, do I need to look for a certain horsepower range? Also can I really just rewire it as easily as I could rewire 1-phase 240 to run on 120, or is 3-phase forever 3-phase? Or can a 1-phase motor be wired to run on 3-phase power but not the other way around? Sometimes a motor is labeled 208V-240V. I had thought 208V referred to 3-phase, so I'm wondering if those motors can, indeed, be switched--but on the other hand, I've also read that 3-phase motors are "simpler" than 1-phase motors. – rob Apr 26 '15 at 2:38

From fine woodworking, you have a few options for running 3 phase equipment when your power lines are single phase. Here's a brief summary:

  1. If the manufacturer is still in business, see if they have a single phase motor you can purchase
  2. Purchase a phase converter. This may be static, rotary, or electronic. (Also see the note about Variable Frequency Drives)

static Reduces available horsepower by approximately 1/3, will have difficulty with heavy starting loads. Not recommended for compressors, band saws, dust collection. This can be offset by having a lower power machine idling constantly, but that seems like a huge waste of energy to me.

rotary Essentially uses the incoming single phase to drive a single phase motor which actually generates a three phase output. Doesn't suffer from the static converter's reduced power problem, but they're not cheap. Here is a guide for selecting a rotary phase converter for your load. Additionally, Kay Industries provides a handy reference for deciding if you need a static or rotary converter. Even if you decide you don't want to use their equipment, it may be useful in making your decision. As an aside, this is a big noisy machine(because a wood shop doesn't have any of those in it normally.)

electronic Commonly and more correctly referred to as an inverter. Converts the signal to DC then creates 3 signals 120 degrees out of phase with eachother, creating a digital 3 phase output. May actually be better than an actual 3 phase power line due to additional control, such as direction and gradual power increase. The article lists bandsaws and lathes as examples of where this would be beneficial (e.g. reversing the rotation of the lathe by reversing your converter's direction). Typically dedicated to a single machine; though, it may be possible to run on multiple machines. Phase Perfect seems to be the go-to for these devices. There is some discussion of them here.

VFD Another option not mentioned in the article but that seems to be cropping up on a lot of articles is a Variable Frequency Drive (VFD). These are very efficient and have the added bonus of being able to directly control the speed of a motor. With that said, aside from certain tools like a lathe, drill press, and band saw, I don't think a VFD is the practical choice; it would be a tool-specific sort of thing.

With all this in mind, I think it's probably best to consult the manufacturer/suppliers. Get their take on it (and their take on their competitors. Make them fight eachother, it's fun) once you've decided which type you want, work with them to determine your power needs, and follow instructions on setting up your converter to prevent damage to your equipment or the converter itself via feedback.

Here are some suppliers, shamelessly stolen by the web site linked above. They note that of those listed, only Grainger sells inverters, though frankly I couldn't find any on their site, you may have to do a littel digging:

Ameri-Phase Corporation

Cedarberg Industries

Grizzly Industrial

GWM Corporation

Kay Industries

MSC Industrial Supply Co.
| improve this answer | |
  • Thanks for the explanation of those options. So is it correct to say that there is no chance a machine running on 3-phase power can be "rewired" to run on single-phase without replacing the motor? Or is it possible that a machine might have a single-phase-compatible motor but be wired to run on a 3-phase power source? If so, how would I differentiate this from a motor that only runs on 3-phase? – rob Apr 26 '15 at 2:53
  • 1
    You can take 3 phase down to single phase (that's how the utility company gets you your single phase from their 3 phase utility lines). I am not an expert so I'm going to leave the "how" to you or an electrician, but essentially you just use one phase of the three by tapping two lines. The mechanisms which drive single phase and three phase motors are different (see the link in the comment in your question), I would be surprised if there are motors which can run (well) on either, but I've been wrong before. Give me a moment on the differentiation. – Daniel B. Apr 26 '15 at 3:08
  • 1
    A single phase motor may have a capacitor on it: it will be covered, and probably look like a cylinder under a metal shell. A three phase motor is likely to have 9 wires coming off of it rather than 3. If it's stamped, 120 or 240v should indicate single phase, but I don't think you can take that as a guarantee, for example ccontrolsys.com/w/Electrical_Service_Types_and_Voltages mentions an older 240v delta configuration. If you're not sure and can't find it, I'd go with the capacitor/wires check and test it based on that, bearing in mind you might let out the magic smoke. – Daniel B. Apr 26 '15 at 3:18
  • Excellent answer; if I could i'd upvote it twice. – keshlam Apr 26 '15 at 15:03
  • What is the typical efficiency of the other types of phase converters besides a static converter? Also, if I'm running a static converter with 1/3 power loss, does that mean it simply delivers less power to the tool, or does it draw more power from the wall to achieve the full 5hp output power? – rob Apr 27 '15 at 8:16

You can do it with a phase converter. Basically there are rotary and static phase converters that can convert single phase 220 into three phase. Rotary converters are a solid technology that has been in use since the 1960's. you can operate multiple 3 phase machines off of a single rotary converter. Static phase converters basically allow 3 phase motors to work on single phase, but not at their full rated horsepower.

There are also digital phase converters that create true 3 phase power, but are considerably more expensive.

| improve this answer | |
  • Thanks for the overview. Given a 240V, 20A circuit, what size motor can I support with a phase converter? How great a power loss will there be with a static phase converter, and what power loss (if any) is associated with the other types of phase converters? Are there any other pros and cons to the different types of phase converters? – rob Apr 25 '15 at 23:44

Large semi-industrial machines usually use large semi-industrial motors, and there's a large market for them.

Get as much information as you can off the current motor, then find a large motor supply & repair place in the semi-industrial part of town (it's the area with the large city blocks). This will be a not-quite daily request, and they could very well take one look at the picture, say that's an Acme Model 2800, the single-phase version costs $X (3 in stock) and we will give you $Y for the trade-in on your 3-phase model.

You may find that changing the motor is a simple wrench job, and in total far cheaper than a phase converter.

3-phase engines are a lot more efficient than single-phase models, which is why they are preferred in places where they run all day. You will probably not run it all day and therefore will not notice the hit on your power bill.

| improve this answer | |

I run a 3 phase CNC Lathe in my garage, I use an American Rotary 10 HP phase converter. Install was very straightforward quiet and runs great. I am not sure why but the manufacturer of the lathe requested the use of a RPC and not VFD. My Lathe is 5hp and I was instructed to use 20amp at utility box. Here is a video I took when I first installed it. 3 phase converter

| improve this answer | |
  • 1
    A VFD can damage motors that aren't rated for them, that's probably why the mfr requested you use RPC. – Daniel B. Apr 27 '15 at 13:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.