Here's a thought.
Use a 2nd single phase motor to turn the 3 phase motor. Excite only 1
phase of the 3 phase motor. Then you'll have 3 phases 120 degrees
apart.
73
Bob K4TAX
Jim Smith wrote:
>
> The single phase you are feeding to the motor has 2 sine waves 180
> degrees out of phase with each other. Three phase is supposed to have three
> sine waves 120 degrees out of phase with each other. If you are generating a
> third phase , there is no place in the 360 degree cycle to squeeze in
> another sine wave. You are going to end up with some really dirty power.
> The lathe may be able to deal with the dirty power, but you are creating
> a problem for the rest of the circuits in the home, the utility, and your
> neighbors. This situation is likely to create problems with phase shift,
> cycle instability, transients, overloaded neutral conductors, and
> overheating.
> If the utility finds the source of their problems, they are likely to
> pull your meter to protect themselves, and their customers.
> Jim Smith, KQ6UV
>
> ----- Original Message -----
> From: "jeff millar" <jeff@wa1hco.mv.com>
> To: "Peter Chadwick" <Peter_Chadwick@mitel.com>; <amps@contesting.com>;
> "'William Fuqua'" <Wlfuqu00@pop.uky.edu>
> Sent: Thursday, April 19, 2001 6:02 PM
> Subject: Re: [AMPS] 3 phase transforers and single phase
>
> >
> > I have an old metal lathe with a three phase motor. In order to get three
> > phase power to drive the motor I got a 5 HP three phase motor from the
> junk
> > yard. I connected 240 across two of the phases and it generates the third
> > phase just because it's spinning. It doesn't want to start by itself, it
> > just sits there humming and smelling very hot. To start it, I just turn
> on
> > the power and give the shaft a flip with my foot and it takes off. If you
> > need more power, just connect multiple motors in parallel. When I start
> or
> > reverse the lathe, the motor on the floor hums louder and jumps around a
> > bit...very cool..
> >
> > The voltage generated by the third phase runs a bit less than the the
> other
> > two. Probably not a problem in practice. This trick should work very well
> > to generate three phase power for transformers and rectifier systems.
> >
> > jeff, wa1hco
>
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