cclist at sydex.com
Wed May 5 10:53:54 CDT 2021
On 5/5/21 8:37 AM, Paul Koning via cctalk wrote:
> Incidentally, a way to get three phase power at a frequency of your
> choice is to use a "variable frequency drive". That's basically a
> high power solid state inverter intended to drive three-phase motors
> with a chosen frequency resulting in the RPM of your choice.
> Depending on the model, those can go up to 120 Hz or so, or all the
> way to somewhere around 400 Hz. I have a very cheap one at home that
> runs on single phase 220 volt power, producing up to 3 kW or so at
> anywhere up to 120 Hz. (Made by a company named Teco, amusingly.)
> Most of these and especially the larger ones want three phase mains
> input, though I'm told that even for those you can typically just
> connect them to single phase power (between two of the three inputs,
> leaving the third unconnected) at reduced power ratings. These
> devices are surprisingly cheap, in particular they tend to be cheaper
> than "rotary phase converters" which is how machine shops
> traditionally produce three phase power when their mains is just
> single phase.
Please forgive the null message--too fast with the mouse.
A simple single-to-three phase converter used by many home shops is
simply a 3-phase motor fed single-phase power to one pair and a large
capacitor connected between the remaining lead and the "hot" side of the
power line. Such a motor is an "idler", run no-load--basically a
rotary transformer. Of course, you don't get a precise 120 degree
phase relationship but it's adequate for powering a lathe or mill.
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