you can get a VFD drive for anywhere from around $400 to any large number
you care to mention - my wood turning lathe has one built into it. You can
get some basic information at Minarik (did I spell that right? they have a
web site, www.minarikcorp.com ) and look at their offerings. You can find
the things surplus cheaply, if you know how to work on electronics.

http://www.phase-a-matic.com/ is a source for static and rotary inverters -
I'm told that their static inverter is around $100


"Richard Ferguson" wrote in message
...
I have been hearing about VFDs and other types of solid state controls.
The Phase Inverter seems not to offer variable speed, but lots of
features. I presume similar units are available with variable speed.

However, it would seem to me that you would need a specific variable
speed drive for each tool, that you would not want to walk to the corner
to adjust the speed. That could get pricy.

To me the most practical (cheapest) thing would be to have one convertor
for the whole shop, asuming that you might eventually have multiple
devices with 3-phase motors.

The way I understand it, the alternatives go something like this.

1. Static rotory converter, simple, only gives 2/3 power, probably costs
around $100 for under 5 hp. Probably could be shared by several machines.

2. Rotary converter - full power, could be cheap if you use an old 3
phase motor to make your own, or more expensive if you buy one new.
Could be noisy. Often shared by multiple machines.

3. Phase inverter - solid state, I think that you said $700. I think
that you said that they could be shared, but you lose some of the
sophisticated features in that case.

4. Variable Frequency Drive - the top of the line solution, provides
electronic variable speed control. I would assume the top price. I
would guess that with some machines, you might want to run part of the
machine with the VFD, while running other parts with straight 3-phase
power, like the controls. It would seem unlikely that one would share
the VFD, but maybe some people do.

What is the price range here? Which of these solutions can be shared
between multiple devices? Am I wrong about what I said above? I am
trying to make sure that I understand.

Richard



wmbjk wrote:

"SRF" wrote in message
...

I'm setting up a hobby machine shop and am getting into the issue of 3
phase
motors. Most of the motors are going to be in the 1 to 3 horsepower
range.
For motors of this size, why would I want to have make three phase
power to
run these machines instead of just swapping out the motors for single
phase?

Thanks.
Steve.

Here's a site with some info.
http://www.processcontroltechnologie...seinverter.htm My only
experience is with the Toshiba S7. A very cool product, but probably in
the $800 range. This is the best I could do for a picture
http://www.lbelec.com/toshiba/drives.html It's the one shown in the palm
of a hand. Contact TK Electric at 702 293-2310 if you need more info.
Why would you want one? Smaller wire sizes, variable speed, variable
torque, slow startup, safety cutoffs, etc. Not really needed for
woodworking I don't think, and you wouldn't be able to make use of most
of the sophisticated programming anyway if you were running multiple
motors. Although if you have enough motors, perhaps adding one new
device would be easier than swapping them all.

Wayne