Re: 3-phase current

To: tesla-at-pupman-dot-com
Subject: Re: 3-phase current
From: gweaver <gweaver-at-earthlink-dot-net> (by way of "Terry Fritz (moderator)" <twf-at-verinet-dot-com>)
Date: Sun, 06 Dec 1998 07:45:29 -0700
Approved: twf-at-verinet-dot-com


>Hi there,
>
>Yea, I'm new here.  
>
>My problem is that I just got ahold of a 10KV power supply, and actually
>managed to get all 700 pounds of it to my house-- But I've got no way to
>power it.  Does anyone know the ballpark cost for piping in 3-phase
>current, or what they usually charge for branching it in from a place
>where it's already installed?


If you live in a house and not an industrial park forget getting 3 phase
power unless your rich. You can hook up 1 phase of the transformer to single
phase at our house.  1/3 of the transformer will produce power.  Sence I
don't know what you up to I can't say much more.

If you really have to have 3 phase then you can build a converter.  Connect
240 VAC to L1 and L2 of a 3 phase motor.  Connect a start and run capacitor
across L2 and L3.  The run cap should be 30 mfd for each HP.  The start cap
should be 60 mfd for each HP.  The start cap is in the circuit only a few
seconds then disconnected when the motor comes up to full speed.  Once the
motor is running L3 acts like generator and produces the other phase.  Its
not perfect but its close.  I have built these all sizes from 1 1/2 HP up to
20 HP.  You can put a relay across L1 and L2 to automatically disconnect the
start caps.

If you need a 3 phase motor to build a converter check the phone book yellow
pages under motor repair shops.  3 phase motors are a dime a dozen and free
if the shaft is messed up.  You might be able to get a free motor for a
converter. You don't care if the motor has a shaft of not.  If the shaft is
bent or keyway is stripped, so what, get a hacksaw and cut it off.  As long
as the motor runs it will make a converter.  If you can't get one 20 HP
motor 4 motors in parallel 5 HP each will do. 

Converters are usually used to drive a motor.  This means the converter
motor and the equipment motor are in parallel.  The 2 motors generator to
each other through L3 to make a more perfect 3 phase type power.  As the
motor turns it generates on L3. If you connect only one 20 HP motor across a
transformer it won't be the same as a motor.  The transformer won't
generator.  I should work best to have a minimum of 2 motors in the circuit
to generate 3 phase.

Gary Weaver