-> Bottom line: What is the benefit of Three phase? Can you get more
-> "cluck for your buck" with three phase? i.e. is it more cost
-> effective to run a one hp motor on standard 220 or 3P 208??
Three phase motors are cheaper, lighter, more efficient, easily
reversed, have high starting torque, and will give you fresher breath
and whiter teeth. Unfortunately three phase power can be hard or
expensive to get; AP&L only wants $15,000 to run it to my house, so I
have a rotary convertor for the milling machines and spin balancer.
WRT the question of "what is three phase" someone posted earlier, here
is a simplistic (because that's the best I can do) explanation:
Electricity is produced by three phase alternating current generators.
The "three phase" means you have three single phase AC generators wound
on the same armature; each one is 120 degrees from the other.
Normal 110v wall current consists of one leg, or phase, and a neutral,
or return, wire. A 220v socket uses two legs and a return. You can
split a 220v socket into two 110s. A three phase socket uses all three
legs. Damned if I know why that doesn't come out to 330v instead of
220, but alternating current gets really seriously strange and there's
not a whole lot between "hook wire A to wire B" and heiroglyphic math.
Solid state phase convertors use two 220v legs and "synthesize" a third
leg to drive three phase equipment. The legs are all supposed to be 120
degrees apart; hearsay picked up from reading the periodic Phase Wars in
rec.metalworking indicates not all convertors manage to produce 120
degree phases. The results, from various self-proclaimed experts, range
from "makes no difference" to "thermonuclear meltdown."
The cheap solid state phase convertors lack start-up power,
particularly for equipment like my Coats spin balancer. My Brown &
Sharpe horizontal mill not only has less starting load, it even has a
clutch, which is seriously unusual on a mill. So to get start-up power
you need a rotary convertor. Underneath all the mystery, a rotary
convertor is just a three phase motor with a solid state convertor.
The convertor lets the motor self-start, and the motor (sometimes called
an idler motor) does the actual phase conversion. Lots of people
dispense with the electronic gadgetry and spin them up with a piece of
rope before switching on the juice.
====dave.williams@chaos.lrk.ar.us========================DoD#978=======
can you help me...help me get out of this place?...slow sedation...
ain't my style, ain't my pace...giving me a number...NINE, SEVEN, EIGHT
==5.0 RX7 -> Tyrannosaurus RX! == SAE '82 == Denizens of Doom M/C '92==
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