Common (non-solid state/brushless) motors:

* Series DC motor, shunt DC motor, universal AC DC motor: Direction
determined by relative wiring of stator and brushes.

* Permanent magnet motor: Direction determined by polarity of DC (or
PWM etc.) input.

* 3 phase AC induction motor: Direction determined by phase relationship
of 3 connections. Swap any two pairs to reverse motor.

* Single phase AC induction motor: Direction determine by relative phase
of run and start windings during starting. Start winding only used
during starting, cut off by centrifugal switch, starting relay, or
other starting device. Main winding conencted directly to mains; start
winding through capacitor or has different inductance/resistance to
provide phase shift.

* Split phase AC induction motor: Direction determined by relative phase
of two windings. Main winding conencted directly to mains; phase
winding through capacitor or has different inductance/resistance to
provide phase shift. Both windings powered when running.

There are many variations.

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(Wolfgang Allinger) writes:

On 18 Jun 15 at group /sci/electronics/repair in article

wrote:

Just wanted to get back to the group about this AC motor that was
running in reverse after being disassembled and then put back
together. It turns out that reversing the brushes did indeed reverse
the direction of the motor. We can't argue with success, but I still
don't fully understand why this is so. Can anyone please explain this
to me? Thanks, Lenny

Take a DC Motor. The brushes are directly connected to the + -
connector. The permanent field is fixed. If you inverse the Batterie,
the rotor will run in the other direction.

So do the AC Motor. However the brushes and the field is connected to
the mains connector, so changing the mains connector will also change
the field, therefor no change between field and rotor.

But you managed reversing by changing the internal brush connection. So
the rotor is now to the opposite of the field direction.

Hope my Ginglisch is understandable


Saludos (an alle Vernünftigen, Rest sh. sig)
Wolfgang