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RE: 3 phase converting

Original poster: "Matthew Carlson" <mjc8804@xxxxxxx>

That is some great info.  We don't much use 3 phase in residential here,
but it seems to make alot of sense.

>>> "Tesla list" <tesla@xxxxxxxxxx> 1/18/05 8:35:24 AM >>>
Original poster: "Gary Weaver" <gary350@xxxxxxxxxxxxx>

It is not necessary to build a 3 phase converter that is complicated.

Connect the 2 wires from the 240 volt ac directly to the 3 ph motor
a double pole switch.  L1 and L2.

Connect a run capacitor between the unused wire of the 3 ph motor to
one of
the other motor wires.  L3 to L2.

Connect a start capacitor in parallel with the run capacitor using a
momentary ON timer relay set to 1 second.  To make it very simple the
can be replaced with a normally open push button switch.  Push and hold
button to start.  When the motor comes up to full speed release the

The RUN cap should be 30 mfd per horse power.  A 5 hp motor needs 30 x
5 or
150 mfd.  Gray color oil filled cap.

The Start cap should be 60 mfd per horse power.  A 5 hp motor needs 60
x 5
or 300 mfd.  Black color plastic cap.

Then the power is turned on the 2 caps are in the circuit.  The caps
provide a signal that fools the motor into thinking it is running on 3
phase so the motor starts.  Once the motor comes up to full speed the
drops out the start cap.  The run cap stays in the circuit all the
The 3ph motor will run on 2 winding.  With only 2 windings producing
the motor will run at 2/3 power.   A 3 hp motor will produce 2 hp.

The unused winding of the motor pics up the magnetic field and acts as
generator.  If you connect another motor in parallel the 2 motors
power to each other and both motors will run at full power.   One motor
NOT USED and is called the ROTOR motor.  It the rotor motor is a 5 hp
it will run 3 other motors of equal HP or a total of about 15 hp so be
to use wire large enough in the circuit to handle the current.   The 5
rotor motor will also power any combination of motors up to about 15
You can run 15 different motors all 1 hp each on a 5 hp rotor.  You can
7 motors all 2 hp each.  You can run one 5 hp, one 3 hp, one 2 hp, one
4 hp
motors.  You can run ten 1 hp motors and one 2 hp and one 3 hp.   Any
combination up to 3 times the size of the rotor motor.

If you have a work shop with a milling machine, lathe, grinder, air
compressor, etc. and the largest motor in your shop is a 5 hp then
build a
5 hp motor starter with 2 caps.  Connect all the machines in parallel
the same circuit.  The 2 caps will start and run any piece of equipment
have in your shop and make it run at 2/3 power.   Suppose you are using
surface grinder and 2/3 power is not enough power then turn on the
machine and let the motor run but do not use the milling machine.
milling machine motor will act as the rotor in the circuit causing the
surface grinder to run at full power.   Any motor in your shop can be
turned on and used as the rotor.  If you need a rotor motor running all
time then buy a damaged 3 phase motor from a motor repair shop.  3
motors sell as mixed metal at the scrap yard for 2 cents a lbs.  A 5
motor new aluminum style will weigh about 50 lbs.  Offer them $5.00
they will probably sell it.  Some shops pull the copper wire from old
motors it gets them a better price on copper but they have to pay
to do this so there is not much advantage to it unless they have
with nothing to do and they have to pay them anyway.   A damaged motor
a bent shaft, damage keyway, broken mount will work fine for a rotor.

Gary Weaver

> [Original Message] > From: Tesla list <tesla@xxxxxxxxxx> > To: <tesla@xxxxxxxxxx> > Date: 1/17/2005 6:48:39 PM > Subject: 3 phase converting > > Original poster: "Jim Lux" <jimlux@xxxxxxxxxxxxx> > > Ran across the following, which may be of interest: > http://www.airraidsirens.com/proj_3phase.html >