Phase inverters (looking for advice)

[barbqman]

I've just purchased a Clausing 8520 Milling machine which has a three phase motor. I want to use it in my basement shop which only had single phase power. It seems reasonable to use an electronic inverter so that I also can control the speed easily. Can anyone give me some advice as to which brands, etc. I should be considering?

Thanks for your help,

[J Tiers]

Three choices...... in order of increasing cost

Static converter...... Starts and runs a 3 phase motor from single phase. Runs it with none of the advantages of 3 phases, but DOES run it.

Rotary converter. Provides good 3 phase power, pretty much equal to a 3 phase line. Can be made from a surplus 3 phase motor of about 1.5 x the power of the one you want to run.
Needs a contactor and overcurrent protection external to it, but will allow tolerating short overloads almost as well as a 3 phase line.

VFD (Variable Frequency Drive). Electronic inverter, can run from 1 phase and produce 3 phase. Allows speeding and slowing motor from nominal speed, gives good overload and overcurrent protection.
MAY require a better-made motor to withstand the harsh power waveform it provides, and does NOT tolerate an overload as well as a rotary converter, will shut down fast.

[SteveM]

Try searching here:

http://www.practicalmachinist.com/vb/fo ... y.php?f=11

That's the phase converter / VFD forum at practical machinists.

Just as I submitted, JT respoded.

Static converter...... Starts and runs a 3 phase motor from single phase. Runs it with none of the advantages of 3 phases, but DOES run it.

JT - what is the static converter "missing" so to speak, in terms of the advantages of 3-phase? I picked up a 1-3hp converter at a garage sale for a buck, but haven't anything to run on it yet.


Steve

[MikeC]

Static converter doesn't deliver anything near full power, maybe 2/3 of rated (rotary is about 80-90%). Your 1hp mill (which isn't very much to begin with) is now a 2/3hp and is liable to run hot if pushed.

I'd actually re-arrange that list and put the rotary at the bottom as far as price. If you can scrounge up a running 3-5hp motor, teh rest of the components for a switch start converter are under $100. As suggested, see the PM forum.

[JHenriksen]

I like to use Hitachi inverters. The SJ 200 series gives good torque at slow speeds down to about 30% of full speed. AC Tech, TECO, Telemechanique are also good brands. I have a WEG rated at 2 hp running my drill press. It was cheap but the external controls still confuse me. Check dealerselectric.com and driveswarehouse.com

[calgator]

Keep in mind any off-the-shelf rotary phase converter is not going to provide a balanced output between each phase of a 3-phase. If you build your own you can then "tune" it to your demands. If you have other 3-ph motors or will aquire some take this into account.

I'm not an electrician but built my own with a used 5 hp motor and about $65 in new capacitors. I pulled a 150 mfu out of an old AC that was going to be scraped.

It does well with my 3-hp Rutland mill once I balanced the capacitors with trial and error when cutting a piece of scrap metal.

below are some links I used:
http://www.metalwebnews.com/howto/phase ... erter.html

http://home.att.net/~waterfront-woods/A ... verter.htm

http://homemetalshopclub.org/projects/p ... hconv.html

[Rich_Carlstedt]

Try Dealers Electric for low prices and good service.
I am a hobbiest..no relation to them
Both Hitachi, and Teco are good.
I also like Mitsubitchi

Rich

http://www.dealerselectric.com/

[Bill Shields]

I have a KAY rotary converter and it produces VERY GOOD 3 phase power...good enough to run several CNC machines and everything else in my shop for years. I can start a 20 HP motor no sweat...

Caution on VFDs....

when running at low speeds, you CANNOT expect to have high torque available without going through the original gearbox...which of course, keeps the motor a-spinning...AND, you cannot use the original on / of / reversing switches...once the VFD is connected to the motor, it needs to be a hard-wire-no switches connection...

Unless you like purchasing replacement drives regularly....

[J Tiers]

JT - what is the static converter "missing" so to speak, in terms of the advantages of 3-phase? I picked up a 1-3hp converter at a garage sale for a buck, but haven't anything to run on it yet.
Steve

it runs the 3 phase motor on single phase....... I mean that in general it does not create ANY 3rd phase. A few have a "run capacitor" that provides a partial imitation of a third phase.

So the smoothness of three phase is not present, you still have the 120Hz and nearly 100% torque ripple. Torque ripple is a major contributor to chatter, especially the roaring and uncontrollable kind so common on small lathes.

True 3 phase has only about 15% torque ripple, maximum. That means most chatter will be far easier to deal with than using single-phase power.

The main feature of the static converter is just that it will start the 3 phase machine.

A rotary can be almost as cheap as a static, if you have the motor. If you want "automatic" starting, the rotary converter is essentially a static converter hooked to an idler motor.

So if you have an "automatic" (no fiddling) start, you need the parts in a static converter, PLUS the motor. That is why I listed the price order as shown.

If you "rope start" the idler, you can make the rotary almost for free if you have a suitable motor for use as an idler.

[MikeC]

Many folks build a lot bigger converter than really needed. I had first heard twice the coverter of the largest motor. This is true only if pulling a really hard start item like an air compressor or huge tablesaw that has a heavy startup pull.

I am also running a home grown 5hp that I balanced, like Calgator. I have several machines running on this converter, generally one large or maybe two smaller ones at the time. I can run my 5hp L&S all day long taking REAL heavy cuts with no heating of the lathe or idler motor. 5hp converter with a good distribution plan is lotsa plenty for most home shops running no more than 5hp machines. If you have anything large, use a matching idler. If you have a three pahse air compressor, then you'll need about double hp.

[RET]

Hi,

If you are looking for a variable frequency unit, Reliance is a good make. While they aren't the only choice and I'm sure they aren't the cheapest, I've had good luck with their MD60 series. Don & I installed one on his vertical mill two years ago & he's had no problems.

Personally, I run my machines on Reliance DC drives because I got the units from work for free. Been using them for more than 10 years with no problems. Make sure you use the control for any starting & stopping or speed change, Do NOT try to switch the output from the drive. As I've said before, when properly installed, they are a "install & forget" device. Also for AC drives, be sure the drive will handle more than the rated motor capacity.

Just my experience.

Richard Trounce.

[recoilless]

There was a good thread concerning VFD's on the HSM site just last week IIRC. Forrest Addy spoke at length on the subject, JTiers also contributed.
I found it to be quite educational. I've got a phase-a-matic 3hp RPC running my Rockwell. It ran too hot outta the box, had to switch out running caps to bring the voltage down. That got me back down to my starting point. The mill has a 200 v motor(yes, 200) but that's a bit of a different topic.
I'm not a VFD owner, have nothing against them, but I'm happy with the RPC I have.