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In article ,
(~Roy) wrote:

It has to do with rotation of a motor....
Motor is a simple aquarium pump, submerged type, powered by AC current
of 115 VAC........2 wire power cord. Armature is the typical magnetic
type. Seems folks are dreaming that they can reverse rotation by
reversing the plug in the recepticle.......SOme have even gone to the
extremes of filing down the wide blade on the polarized plugs so they
can put plug in either way and think they are reversing
direction......Is it possible to change rotation of a AC motor like
this or not? If not, how about an explanatin why, and if it is doable,
an explanation as to how would also be appreciated........No other
mods to motor, just simply reversing plug orientation to reverse motor
rotation.....Not any need to get into the fact that the pump probbaly
would not work or work properly with a wrong rotation due to volute
design etc........

For small single-phase AC motors, the direction of rotation is
controlled by the design and construction of the motor, not by the power
source.

Aquarium pump motors are usually shaded-pole induction. Look for a
shorted copper turn on at least one laminated steel field pole, covering
about one half of the poleface. It's this shorted turn that determines
the direction of rotation. To reverse rotation, move the shorted turn
to the other half face. Or take the motor apart and reassemble it with
the pole assembly reversed, if the motor construction allows this.

Joe Gwinn