"Christopher Tidy" wrote in message
...
Ignoramus23077 wrote:
thanks to everyone for your thoughts!

Many pictures and the story in several chapters:
http://igor.chudov.com/projects/Phase-Converter/

Wow, you certainly work fast! Glad it's working so far. It looks like you
got some nice equipment at good prices, too. Your induction motors look
quite different from the ones we usually get in the UK. The majority of
our three phase motors are either the standard aluminium TEFC motors or
the older cast iron type, of which there are still many around. Yours look
somewhere in between these.

For the experts on phase convertors, I've got a couple of questions. I'm
thinking of building the kind of convertor Dan Caster was talking about,
where a small single phase motor permanently drives a larger three phase
motor through a variable belt drive. The three phase motor has two
terminals connected to the single phase supply and generates on the third
terminal, and the belt drive ratio is adjusted so that the single phase
motor draws its rated current when the phase convertor is working at
maximum output.

Now my questions. Firstly, will the quality of the three phase output be
improved if the single phase motor is larger than a typical pony motor
(e.g., 3/4 hp single phase motor and 2 1/2 hp three phase motor)?


No difference in the 3 phase output. The pony is needed only to provide
enough RPM of the 3 phase idler so it will spin up to its no load max RPM.
Once the idler is spinning, the pony can be disconnected.

SNIP

Secondly, would the addition of a
flywheel to the idler motor shaft (not necessarily together with the
permanent drive from the single phase motor) help balance the output?


No again, the idler RPM doesnt vary (measureably) with toolmotor load
related RPM. Actually, the flywheel hinders the idler's acceleration when
it is initiated.



Again, I intuitively think it would, but I'd be interested to hear the
views of others.

Best wishes,

Chris