AC Induction Motorshttp://upload.wikimedia.org/wikipedia/commons/b/b5/Tesla_induction_motor.gif

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AC motors• It is possible to use a normal DC motor as an AC

motor (the only difference is that it will have a slip ring commutator).

• However, there is a much more common AC motor called an induction motor. Induction motors usually harness 3-phase supply and are superior for a number of reasons.

• AC induction motors have two main components - the stator and the rotor.

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The statorThe stator consists of multiple stationary coils of wire which are fed by the AC supply. It surrounds the rotor.

http://en.wikipedia.org/wiki/File:Rotatingfield.pnghttp://www.basilnetworks.com/article/motors/images/motor2pole.gif

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The rotorThis is a freely rotating series of parallel conductors positioned inside the stator. The rotor is often called a ‘squirrel cage’ due to its shape.

http://avstop.com/ac/apgeneral/imageevd.jpg

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How does it work?• The stator coils work together in pairs (opposite

each other) to create a magnetic field which rotates around the motor.

• This constantly rotating magnetic field induces eddy currents in the rotor, which gives rise to a new magnetic field.

• This new field interacts with the original (stator) field to create a torque. The rotor spins, following the direction of the stator field.

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Why are they better?• There are no brushes or commutators since

current is induced into the rotor. This means the motor won’t wear out quickly, and will experience less friction.

• Induction motors have a much more consistent torque around one revolution. This makes them more useful in commercial applications.

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http://www.mindconnection.com/images/library/motorslip/AC%20Induction%20Motor%20cutaway.jpg

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