In article Ngjxd.317$Y57.170@trnddc08,
Jerry Martes wrote:
[ ... ]
I dont know how to analyze this 3 phase motor that is using only 1/2 its
windings (poles) to spin it. But, it surprizes me that an induction motor
can still run when the number of poles is reduced to 1/2.
But the number of poles may *not* be reduced to 1/2 the normal
number. If the split windings are on the same physical poles, and only
electrically isolated, there should be no problem. I just got through
typing a fairly long response (which you will not yet have had a chance
to see) in another branch of this thread.
I wonder if a 4 pole motor can be re-connected to be a 2 pole motor.
It depends on the design. Two-speed motors are connected just
this way. I have even had a three-speed (2-pole, 4-pole, 8-pole) as the
capstan motor on a reel-to-reel tape deck. It also was designed as an
"inverted rotor" one, so the rotor doubled as a flywheel. Actually, it
had three independent sets of windings. It was a cap-run motor, and
fairly low torque. I spent some time learning to re-wind motors when
that one burned up. And then, once I got that right, the bearings gave
out. :-) It *did* come from a hamfest, and the whole deck cost me
something like $2.50. :-) I later got an Ampex 440B to replace it. And
the 440B has a two-speed (by switched windings) Hysteresis-synchronous
motor -- with a separate flywheel. The motor was made by Bodine.
But,
this gets too complex for me to analyze. I'd have guessed that the
re-connected motor would produce a torque that contained ripple.
That's the reason for the flywheel. :-)
I'd sure like to know more about how a 3 phase motor can be made to spin
when 1/2 itys poles are removed (not connected).
Because, in reality, all of the *poles* are energized -- just
separate coils sharing each pole. This is apparently a function of who
made the motor. Some have shared windings and can act as an
autotransformer, some have separate windings, and can't.
Enjoy,
DoN.
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