3-phase power

Chuck Guzis cclist at sydex.com
Tue Jan 4 12:35:31 CST 2022

On 1/4/22 10:04 AM, Paul Koning via cctalk wrote:

> The other option, typically somewhat more expensive but cheaper than an 11/780, is a rotary converter.  Those are 3 phase motors, sometimes modified a bit, driven from single phase power that construct the missing phase somewhat like a dynamotor would.  Those things produce proper sine waves so they are good to use even with things that are picky.  Rotary converters can be found in machine tool supply catalogs.

One has to be careful here.  The common "idler" type of rotary converter
uses a 3-phase motor, with only one set of windings fed from the single
phase supply and leading the third phase idle to develop a current
that's +/- 90 degrees from the powered phase.   So the output looks like
0,90,180, rather than 0 120 240 degrees.   Good enough for powering a
3-phase motor with slight derating, but nothing I'd use to power a
computer power supply.

The second type is similar, but incorporates a dual field arrangement,
with a single-phase field coaxial with a 3-phase one comprising a motor.
 You get much better output phase relationships there and one would
probably work fine with a computer.


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