19 Jun
2014
19 Jun
'14
7:13 a.m.
On Jun 19, 2014, at 12:08 AM, Chuck Guzis <cclist at sydex.com> wrote:
On 06/18/2014 05:39 PM, Paul Koning wrote:
Those are rotary converters, and when built correctly they have excellent phase balance.
Some of the articles discuss in detail how to achieve that. Basicallly, those are rotary
transformers, very similar to the old ?dynamotor? power supplies found in WW2 era military
radio gear. Think of it as a motor and generator, merged together.
You can buy them commercially at machinery supply companies, but the DIY kind you describe
are essentially the same thing and can be much cheaper if you can find the motor component
cheaply.
paul
Rotary converters are effective but pricy. Solid
state variable
frequency motor controllers (basic ones) are a lot more economical.
They will do for a few kW of 3-phase power. They will also serve if
you need a different frequency ? not usually a consideration but it
matters if you have an old Cyber, or possibly some military surplus
gear.
Home machinists often do a DIY by using some capacitors and a surplus 3-phase
"idler" motor. I wouldn't give a plugged nickel for the phase balance, but
it works well enough for some motors. I have a friend who runs his West Bend lathe that
way.
See, for example:
http://www.nojolt.com/how-to-build-a-rotary-phase-converter.shtml
--Chuck