Getting 3 phase at home

So a buddy of mine is looking to buy a large lathe/mill. We've found a few at reasonable prices, but they're 3 phase. 

I've done a little looking around, and supposedly, there are some easy sounding ways to make it work at home. I don't know if I believe it though, because this is way outside of anything electrical I've ever done. I guess I'm just looking for confirmation or suggestions.

Method One: hook up a capacitor between the legs of the motor. 25MF per horsepower keeps coming up on searches, but includes the caveat of needing some sort of starter.

Method 2: diesel generator. Clearly expensive, and noisy, but makes sense to me.

Method Three: I don't remember the specifics, but it was something about using a seperate electric motor, possibly on a separate circuit, and combining voltages? Ok, I was half asleep when I read this one, but it doesn't sound right at all typing it out.

Aside from the diesel generator, are these viable options that won't explode or short circuit my house?

What I do have is a 50 amp sub panel with 240 in the garage. It feeds another panel down in the carport with same voltage and current. We also have a running 5.9 Cummins in the Snap On truck that currently feeds 120v, but we believe could produce more electricity while still running the truck.

So are we idiots for even considering such a thing, or could this actually work out somehow? I'm more interested in the possibility of a cheap 3 phase welder or air compressor, but he's pretty hung up on a cheap mill setup. 3 phase stuff is annoyingly cheap which is what got our attention in the first place.

RevRico said:

 

Method Three: I don't remember the specifics, but it was something about using a seperate electric motor, possibly on a separate circuit, and combining voltages? Ok, I was half asleep when I read this one, but it doesn't sound right at all typing it out.

 

Rotary Phase Converter. They have been around a long time and this one seems cheap enough. I don't know your amperage requirements.

Rotary Phase converter

mad_machine said:

RevRico said:

 

Method Three: I don't remember the specifics, but it was something about using a seperate electric motor, possibly on a separate circuit, and combining voltages? Ok, I was half asleep when I read this one, but it doesn't sound right at all typing it out.

 

Rotary Phase Converter. They have been around a long time and this one seems cheap enough. I don't know your amperage requirements.

 

Rotary Phase converter

Came in to say that, although much less articulately.  The guy who was previously in the space that I occupy was running a bunch of equipment off of some type of single phase to three phase converter system to do commercial work 6 days a week, 10 hours a day, so apparently that works fairly well.

My friend used rotary phase converters in his pole barn for the exact same reason that you are looking at them; he bought a commercial 3 phase milling machine and lathe.  Never had any problems that I had heard of.

In reply to mad_machine :

That's what I couldn't think of. And wow, that is fairly inexpensive. Also seems a bit safer than adding capacitors unnecessarily, I have a history with making those pop. 

Some good reading

http://www.kayind.com/common-phase-converter-issues-and-misconceptions

Yeah I would not be randomly hooking up (large) capacitors between motor poles unless you have a very solid understanding of what you are trying to do.

Phase converter sounds right. 50 amps sounds like not enough.

How big are the machines you are trying to run?  If they are high horsepower, suggest just renting a place with 480V already.  

For home use 3HP and down there are a few good ways to do it.

• Find a machine that is set up for single phase or change the spindle motor out for one that is single phase.  These do exist but are tough to come by.  The actual controls, etc are generally 120VAC 1PH or 24VDC with a transformer off mains power so these can be run on alternate methods relative to your main spindle.
• Take off the spindle motor and have it rewound to be single phase.  This is doable but would cost some serious cheddar.  If the motor can be replaced by a single phase motor that is the easy button.
• Run the spindle motor off a VFD aka a Frequency Drive.  Frequency drives take single or 3 phase input (derate for single phase) and convert to DC and then convert back to AC 3 phase.  120VAC or 240VAC 1PH can be converted into 240VAC 3PH with a single simple solidstate box.  Downside is a frequency drive for any sizeable horsepower requirements cost real money and they are derated when using single phase input - IIRC its 2/3 of rated output but I could be wrong.

Something like below would run up to 3HP 3PH off of 240VAC 1PH and gives you the benefits of speed up/slow down/reverse/brake all in solid state. 

I am running my drill press on 120VAC 1PH off a KB Drives frequency drive with a 1/2 horse 240VAC 1200 RPM 3 phase motor.  Works great.  

https://www.automationdirect.com/adc/shopping/catalog/drives/ac_variable_frequency_drives_(vfd)/gs2_(115_-z-_230_-z-_460_-z-_575_vac)_v-z-hz_control/gs2_drive_units_(115_-z-_230_-z-_460_-z-_575_vac)/gs2-23p0

I built my own rotary phase converter and use it to rum my hoist and milling machine.  It consists of a 3hp single phase pony motor, a 15hp  3 phase motor, one 30A single phase disconnect, one 30A 3 phase disconnect, a 3 phase splitter along with the related conduit and wire. I wouldn't suggest taking this approach without the technical knowledge.  

 A prepackaged unit will serve you well for years. As noted a VFD will also work but gets into big bucks when you start adding load sizes.

In reply to RevRico :

So how many HP is the mill?  That's going to help steer you to the right answer.

In reply to 1988RedT2 :

Majority of what we're seeing are 2 to 3hp. So basic rotary phase converter should work fine from my 50 amp panel.

Knowing Mike though, I'll get a call one night he got some 50hp mill for a nickel cause nobody wanted it and we'll need a miata to power the thing. 

But realistically, narrowing the search to 3hp or less shouldn't be a big deal. I honestly just want a metal lathe or a small CNC machine to do material under 12 inches, and while I do see them that run on regular old 240V, there's a lot more of the 3 phase ones a lot cheaper.

He's also got this goofy idea of converting the snap on truck to a mobile machine shop, but even I think that's too out there to investigate. 

I also have a rotary phase converter running in my garage to power up my 3 Ph Quincy two two-stage motor compressor that I got for ridiculously cheap.  It works well.  I have the phase converter with a contactor and a momentary switch ran down in the garage to get the phase converter started, then used a 3ph light switch to turn the compressor on once the phase converter is spinning.

If I had to buy new, I'd go VFD, no question, though.   Cheaper, easier, solid-state-ier.  Back when I hooked up my RPC, VFD was prohibitively expensive.  I found my RPC on craigslist for like $250...

If you are only looking at one piece of equipment on the smaller side then VFD is the way to go (and adds variable speed to the machine if that is useful). Smaller drives you can get with a single phase input and 3 phase output, these do not need to be derated. Once your demand is above those you can use larger 3 phase input units but you need to derate as mentioned above (take the drive output amps and multiply by 0.577 and that will give you the output amps with single phase input).

If you are thinking of more 3 phase equipment then the rotary phase converter is the way to go, size it to your largest load at one time (maybe an air compressor + the next largest load) to get your ideal size. The reality is though you will be limited by that 50 amp breaker (80% load on that is 40 amps x 0.577 = 23 amps 3 phase roughly).

Adam

Just throwing a few ideas out...

Maybe install a small VFD (variable frequency drive) with single phase input and 3 phase output.  Similar principle to the phase converter.

Or change the three phase motor out for a single phase motor?

*edit- oops, didn’t see the VFD was already suggested

SIngle phase 230V input. 3HP 3 phase output

automation direct

The easy button for a single machine. Smaller and cheaper than a rotary converter. Cool features like motor speed control, torque boost and immediate safety stops.

Jumper K Balls (Trent) said:

SIngle phase 230V input. 3HP 3 phase output

automation direct

 

The easy button for a single machine. Smaller and cheaper than a rotary converter. Cool features like motor speed control, torque boost and immediate safety stops.

Echo...echo....echo...

In reply to 93gsxturbo :

Odd. I skimmed the thread and missed that.

Great minds...alike and all that 

In reply to 93gsxturbo :

Was it actually hard to build that thing? Just curious

I am running a 3-phase mill and a 3-phase lathe at home, both with their own VFDs I bought from Dealers Electric, the cheapest source I could find at the time.

I love the 3-phase power!

I also love the variable frequency to fine-tune motor speed, as well the "jog" feature.

Installation was easy, and I have a super short video from years ago on each:

SilverBrick said:

In reply to 93gsxturbo :

Was it actually hard to build that thing? Just curious

My drill press?  Not at all.

3 Phase Marathon motor from Ebay (1/2HP 1200 RPM) was $60 or so.

Pulley from local farm supply store was $10

Belt from the same was $10 or so

KB Drive was $165 from Amazon.

 https://www.amazon.com/KB-Electronics-KBMA-24D-Enclosure-Frequency/dp/B01AOCJT0K/ref=sr_1_1_sspa?keywords=KBMA-24D&qid=1564154771&s=industrial&sr=1-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzUFBJRzFRRENaM0RGJmVuY3J5cHRlZElkPUEwMjE2MTQ3M0s1TUVTSDEwQUZDRyZlbmNyeXB0ZWRBZElkPUEwNDMzNzkzM1ZHTUlNNjJEQlJOSCZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

Wire it all up took minimal three phase knowledge, I know the stuff because I work with it but its nothing some googles couldnt answer or I can walk you through it.  

I have it set up so the original on-off switch on the drill press is now forward-brake-reverse, on/off and speed are on the drive.  I made a little bracket and sandwiched the drive mount between the motor and the existing motor frame on the drill press.

Only downside I have read is some of the KB drives without a line filter will trip a GFCI outlet.  My drill press is not on a GFCI so I don't care.  

I did some maths to determine the right size pulley for the motor to give me a good speed range for the sort of things I drill using 0-120hz - one nice thing about a VFD is they can run a motor at 2x rated RPM by doubling the frequency going to the motor.  Good rule of thumb is you are good running 20-100 hz no issues, anything below 20hz should have an aux fan on the motor to keep it cool if you are running 100% duty cycle, anything above 100hz will shorten bearing life.  I don't care because it was a $60 motor from Ebay - if I burn it up I will throw it in the gutter and go get another.  Technically a motor should be "inverter rated" if you want to run it on a VFD - they have better fans and insulation.  Practicality, unless you are running 100% full load amps, 100% duty cycle, in 100 degree ambient heat, you are fine to use a non-inverter rated motor in a hobbyist application.  

I have an Ebay vfd on my ironworker and it works great. 

SkinnyG said:

I am running a 3-phase mill and a 3-phase lathe at home, both with their own VFDs I bought from Dealers Electric, the cheapest source I could find at the time.

I love the 3-phase power!

I also love the variable frequency to fine-tune motor speed, as well the "jog" feature.

Installation was easy, and I have a super short video from years ago on each:

https://www.youtube.com/embed/Qia0gHijOYY?rel=0

 

https://www.youtube.com/embed/DnEDExrtrtU?rel=0

 

Thanks for sharing a couple of videos. I also love that.