Do 3 phase converters work well, or are you better off replacing the motor(on a mill, in this case) with a 1 phase? Looks like the rotor type is more efficient than the static, but it looks as though you lose a little horsepower either way.

Thanks,

Jeff

I have a static on a pretty good size metal lathe 10 x 72....

Static uses electronics to make the motor run,but you loose horsepower.Instead of 3 overlapping legs of current,you only get one.
In my application,wood and light metal work,it's not bad.....

The guy I bought the lathe from runs a 8 x 36 Bridgeport verticle with one and is happy.

Many people in small commercial wood shops have rotaries.While you get full power,because your generating 3 phase of your own,it comes at a cost.The amperage drawn is high,meaning that your electric bill is also.

High torque requirments,say a large fly cutter,or in my case a 12" table saw;don't do well with static converters.But gunsmith small parts would be no problem.

Hope this helps;

Dan

I run a surface grinder on a rotary.....it works just fine.....

I run my lathe, mill and surface grinder off a 10hp rotary system and it works flawlessly. I can run all three machines at once if I need to. My gas and electic runs around $50 a month and that's with me in the shop about 60 hours a week. I planned the installation when I built the building and installed the idler motor in the compressor shed on the outside of the building so when its on I can't even hear it, which has on occasion led to me leaving it on all night.

Wanted to add that this is a 1/2hp 3ph motor, on a vertical mill.

Thanks for sharing your experiences, guys!

Jeff

If it is a step pulley, get a VFD. You will gain variable speed and not loose the voltage that you will with a phase converter. They make no noise.
Butch

I have three phase at the alley and could solve the phase converter problem by simply running in a new 3 ph 200 amp service to serve the whole building. My issue is whether or not the Chicago area rate for 3 ph would tend to be predatory compared to 240 v single. I should ask the electric co. Outside of sawing lumber I probably have no serious need for it but I have a compressor and a hydraulic pump which have 3 ph motors. I would just as soon not have to replace them.

I did ask for a quote on three phase converters for several machines but this blew the contractor's mind as they never had such a request so the deal never went anywhere.

I run my lathe on a static converter and if it wasn't mounted where you could see it you'd never know it was there. It works really well.

Jeff,
a Static converter will run you 70 bucks and only deliver to you 2/3 of the power. A rotary converter will run you quite a bit more. If I were you I would get a nice, clean, used motor for about ten bucks at any flea market and have a go with it. Most motor shops will sell you good used motors of that size as well. With just a 1/2 h.p. motor you dont want to be lowering your output!

Do a search on EBay for variable frequency drives. I have 2 rotary converters and 2 VFD. I use the VFD on both of my Bridgeports. My bandsaw and lathe are variable speed and run off the converters. My surface grinder does not need variable speed.
In the old days I had a static converter and didn't know I was missing anything until I changed.
A single phase motor will show up in a turned finish sometimes on a lathe.
Butch

A rotary converter is a piece of cake to make and works really well. If you do threading where you want to be able to flip the lever (some times called plug reversing) and have your lathe instantly reverse (not a good idea with a threaded spindle) - like threading toward a shoulder, or doing metric threads where one can't disengage the lead screw, a rotary converter is the way to go. Several years ago I put out a design that was first posted on the RecCraftsMetalworking user group. A guy named Jim Hanrahan had done a similar thing a few years before. He and I had slightly different excitation capacitor optimization routines. I spent some time coming up with a way to get close to a loaded voltage balance with out exceeding the voltage rating of the motor windings in the converter. George Carlson also put together a nice discussion of how to build one. George spends more time and circuitry for making the start automatic. My design starts with a momentary contact push button that is pushed and released.

A rotary converter is just a plain old 3 phase motor that is running single phase and generating two additional phases by acting as in induction generator. It is inherently self synchronizing regardless of rpm.

Information about it is available on the Practical Machinist Phase Converter Forum.

The design I documented is here:

http://www.practicalmachinist.com/FitchWConverter.pdf

Jim Hanrahan also did one which is here:

http://www.metalwebnews.com/howto/ph-conv/ph-conv.html

And another George Carlson put together this document:

http://www.homemetalshopclub.org/projects/phconv/phconv.html

This thread has all sorts of pictures of them starting with Jim Rozen's. I met Jim about 12 or 14 years ago on the RCM newsgroup.

http://www.practicalmachinist.com/vb/showthread.php?t=101231

Fitch

www.drivewarehouse.com

get a VFD, for 225 bucks, build a VERY simple reostat control for another 30 and forever be thankful that you are running all three legs at full power...

i use the 12amp one, have had two (first one got sold with manual mill) and it works like a charm

VFD's are GREAT!
They do, however require bypassing your factory switching to turn the power on. I've got 3ph power in my shop and I'm using a VFD on 2 machines.

Anton at http://www.precisionzone.com/
can help.
I got a VFD to run my 1HP Mitsui surface grinder for $150.

It might be easier to buy a static phase conv for around $100.

I made a rotary converter with a 2hp 3ph motor a pulley and a rope.

There's a million ways to skin this cat.

James that is not true on the switching. Both of my mills use the factory drum on-off reversing switch. You just have to be careful to run the power into the VFD and out of the VFD direct to the motor. You run doorbell wire from the VFD to the factory switch.
Butch

quote:

Originally posted by butchlambert:
James that is not true on the switching. Both of my mills use the factory drum on-off reversing switch. You just have to be careful to run the power into the VFD and out of the VFD direct to the motor. You run doorbell wire from the VFD to the factory switch.
Butch

You're right Butch. My point was that you need to do a little more wiring using a VFD than with a static converter. The VFD, if sized properly and wired properly is a much better solution. It's just more involved. You also need to set a bunch of parameters in the VFD after you're done wiring. When the params are set properly, it protects the motor better than a thermal overload and allows you to program the acceleration and deceleration time and vary the RPM as well. This is the reason I use one on my surface grinder. I can dress the wheel and turn the grinder off. I have a 15 second accel time programmed in. When I turn the grinder on, the wheel is still running true. Without the VFD, the motor can start so fast that the wheel spins on the arbor and it no longer runs true. I also turn my surface grinder on for 10 min or so at half speed to warm up the bearings before I grind at full RPM. The only problem I have with the VFDs I use is they produce so much noise that I can't listen to AM talk radio when the VFD is running.

James,
I have static noise with my Hitachi and none with my Westinghouse. We have grounded everything to a common ground pole in the ground outside. Put the radio on a separate breaker and still noise. I just live with it.
You better watch those AM talk radio people!
Butch

Just find an old three phase motor, spin it with a single phase motor, hooked together with a belt. Power your mill off the three phase motor. Three phase motors also generate three phase juice.

quote:

Originally posted by wino:
Just find an old three phase motor, spin it with a single phase motor, hooked together with a belt. Power your mill off the three phase motor. Three phase motors also generate three phase juice.

The single phase motor should be used as a starting motor only. Leaving them belted together running with both powered is not a good idea.

Fitch

quote:

Originally posted by butchlambert:
You better watch those AM talk radio people!
Butch

I know, they're on the endangered species list.

AM will pick up a fart two miles away and trash you're listening pleasure.

Thanks once again, for all the replies/ideas! I think I will start out by researching the VFD option. Interesting concept.

Regards,

Jeff

Seems a pain for such a fractional HP motor , that possibly may be less expensive to run a single phase .

Static converters SUCK . VFD Rotary are just fine . BOL on what you decide .

The more I delve into this subject, the more inclined I am, to just buy a 3/4hp single phase motor, and be done with it. This mill (Rockwell 21-100) came from factory with either a 1/2hp 3ph, or a 3/4hp 1ph. Will just need to find one that will fit, mechanically. Phase conversion is starting to look like a PITA, for just one machine.

Jeff

Jeff,
I think that you will find a VFD for less money than a motor exchange and you are gaining variable speed.
Butch

If radio interference (static generation) is really a problem, its pretty simple to eliminate it no matter how many phases of power you are running. You can buy such filters in neat enclosures for many times the price of the components used in their construction. Or you can build your own, as shown here, then put it in any enclosure which is convenient. Shielding of the enclosure should not be required.

If you know any “oldtime†radio amateur operators, they will probably be happy to help you. Call the local HAM club and ask around.

The way these filters work is by taking advantage of the enormous difference in frequency between the motor AC drive frequency (60 Hertz) and the interference frequency of more than 190,000 Hertz of your lowest-frequency AM radio band. For instance, the 0.1 uF cap which dumps the interfering signal to ground will, at 60 Hertz, dump only 0.003 amps to ground, which will not be noticed. But at the minimum radio-signal frequency of 190 KHz, this 0.10 uF cap presents a path to ground of only 4 ohms, which is pretty close to a dead short. At the same time a 1.1 millihenry inductor presents a series blocking impedance of 1,310 ohms at 190 KHz. So the interfering signal would rather take the 4 ohm path to ground than the 1,310 ohm path to the motor windings where it will likely get radiated to your radio as noise. This is about a 50 dB noise filter at your LOWEST listening frequency. It gets better at higher frequencies. The extra components shown help insure good filter operation at higher frequencies, even including the FM bands.

Parts:

Jameco.com or allelectronics.com supply the needed parts at pretty good prices.

Jameco Electronics has a TRIAD MAGNETICS INDUCTOR, 4.4mH 5.5A E-CORE for $7.49 each, Jameco part number 627479, and you will need one of these placed between your power connection and your motor on EACH PHASE line. If your motor draws more than 5.5 amps when running, you can parallel these, and each will pass 5.5 amps. A few words about this 4.4 millihenry inductor from Jameco. This inductor has two independent windings on it, and when connected properly it will yield 4.4 mH. In this configuration, and with 4.4 amps AC running through it to the motor windings, it will cause an AC voltage drop of about 7 v. AC to the motor windings, which you might notice as power loss to your motor. Probably a better way to use this inductor is to use only one winding. This will reduce the reactance of the inductor to 1.1 millihenry, and reduce the AC voltage loss to the motor windings to less than 2 v.

CAP: 0.1 microfarad 1000 v. ceramic disc CAPACITOR,CERM,DISC,0.1UF,1KV,20% for $2.39 each Jameco part number 332516. The other side of the capacitor is connected to the “earth†ground, like the ground of the lathe-bed.

22 UH, 4 AMP COIL All Electronics catalog number CAT# CR-224, 2 for $1.00. This is a 22 microhenry inductor, and is only rated at 4 amps motor current. But it should really help at high radio frequencies. Try one first, and if it gets hot while running just parallel it with another.

470 PF 2.5 KV DISC CAPACITOR, All Electronics CAT# 471D2.5K, 10 for $1.00