Ac Motors and induction.

A Shaded Pole AC Motor
 
Here is a photo of a typical shaded pole motor.  See the close-up of the notch in the laminations and the extra heavy winding of two turns creating the phase difference between the two sections of the laminations, giving the magnetic field a directional motion.   The rotor spins CW as seen from the end with the screw on the shaft.  Motors like this are used in thousands of applications.
Another Shaded Pole AC Motor
  
Here is a photo of a ceiling fan motor, also shaded pole, but with six windings instead of only one as seen above.  The rotor laminations are skewed to provide smoother torque.   The pole pieces with the windings have a slot in them to create a delayed flux, creating a direction for rotation.


Exploded View of an AC MOTOR.
Below is an exploded view of the AC motors similar to what we have been testing. This is a great photo as it shows all the working parts.

What Spins an Electric Motor ?
The rotor of an electric motor needs a torque to start it spinning. This torque is
normally produced by magnetic forces, exerted between magnetic poles on the
rotor and those on the motor’s stationary shell. Attractive or repulsive forces pull
or push on the outside of the rotor, producing torques that make the rotor spin
faster and faster until friction or the objects attached to it reduce its net torque to
zero. After that point, the rotor turns at a steady angular velocity.
Both the rotor and the motor’s fixed shell are magnetic. The forces between
these magnets are what produce the torques. But while permanent magnets are
often used in electric motors, at least some of a motor’s magnets must be electromagnets.
That’s because the motor can only keep turning if some of its magnetic
poles change or move as the rotor spins. That way, while the rotor turns to bring
opposite magnetic poles as close together as possible, the poles keep changing or
moving so that the rotor finds itself perpetually chasing the optimum arrangement
of poles.

Induction AC Motors

Some alternating current motors have rotors that are neither permanent magnets

nor conventional electromagnets. These rotors are made of non-magnetic metals

such as aluminum and have no electric connections. But their electric isolation

doesn’t keep these rotors from becoming magnetic. When an aluminum rotor is

exposed to changing magnetic fields, currents begin to flow through it and these

induced currents make the rotor magnetic.

Motors that use induction to create magnetism in their rotors are called induction

motors. Induction motors are probably the most common type of AC

motor, appearing in everything from household fans to industrial pumps to cable-

lift elevators. They provide lots of torque, start easily, and are inexpensive.

An induction motor works by moving a magnetic field around the rotor.

The stationary shell surrounding the rotor contains a sophisticated electromagnet

called a stator. While the stator doesn’t move, the field it produces does. Through

a clever use of various electromagnetic devices, the stator is able to create magnetic

poles that move in a circle and travel around and around the rotor.