biodieseler land as we are all a bunch of scroungers and we seem to need
motors. I have found that three phase motors are always really cheap
(often free) because no one wants them because three phase power is not
typically available in non-commercial settings and it is often only
available to larger customers who use a lot of power and pay a lot of
presence fee.
if you have an extra three phase motor and standard 220 power you can
make your own three phase.
"Single phase" 220 is actually 2 phases, shifted by 180 degrees with a
common neutral, that is what the three wires are. If you examine your
breaker box you will find that it has 2 rails or "buses" each of them
connected to a single conductor that comes in from the electric company,
and a third which is connected to the "neutral" line and also to ground.
110 volt breakers connect to one or the other bus line and then you
connect the other lines to the ground/neutral (this is only true in the
main panel, in a sub panel or in a junction/device box neutral and
ground are different) 220V breakers are connected to both buses so they
get both phases of power coming from the electric company. in three
phase you get a third "leg" so now you have four wires. you can actually
run a three phase motor on any two legs but it will produce less power
and, if jolted just right, may reverse direction. so here is the magic,
if you drive a motor it will generate, so you drive the motor on the
first two legs and then grab the third leg for your other motors. the
trick is starting, once you have it going the first motor, the "idler"
spins, leading the phase on the third leg which produces the necessary
current for the other motors to have their three phase. if you have one
really big motor (like a 3-5 horse) and some smaller motors (like one
horse) you can run a few of them off the same phase converter without
any problems.
there are some neat tricks too for example those who understand
capacitors will remember that although they pass AC, they also produce a
phase shift or lag so if you add a capacitor between the first leg and
the third leg of a large enough value you can actually start your phase
converter (or your motors if you don't need their rated power) with just
the regular 220. if your phase converter is rated at more horsepower
than your load and your motors have a service factor of 1.15 to 1.25
(should be on the plate on the side of the motor, probably "S.F.") then
you should get your full rated horsepower.
there is an excellent site on all of this complete with some diagrams here:
http://www.metalwebnews.com/howto/ph-conv/ph-conv.html
here is a PDF that has instructions on building a nicely integrated
phase converter for shop power:
http://www.metalwebnews.com/howto/phase-converter/3-phase.pdf
John Guttridge
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