[AMPS] 3 phase transforers and single phase

jeff millar jeff@wa1hco.mv.com
Sat, 21 Apr 2001 22:34:54 -0400


Jim...

Using a motor as a rotary phase convert is standard, traditional, and works
extremely well.  See the web site below for more discussion.

http://web.wt.net/~hmsc/phconv/phconv.htm

None of the disasters you propose can happen.  The phases will not be
perfectly correct and the voltage balance not perfect either.  But, that
doesn't make it "dirty"...What does "dirty" mean anyway?  The power factor
will also run a bit off.  But so what?  This is a few KW load on a pole pig
rated at 20 KW in a neighborhood drawing 250 KW.  Switching power supplies
and microwave ovens create huge power factor problems and the world hasn't
come to an end.

jeff, wa1hco

----- Original Message -----
From: Jim Smith <jimsmith@bigvalley.net>
To: <amps@contesting.com>
Sent: Saturday, April 21, 2001 7:32 PM
Subject: Re: [AMPS] 3 phase transforers and single phase


>
>     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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>


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