Single Phase AC Motor

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In asynchronous motors the induction principle is used, whereby a conductor is placed in anelectromagnetic field which is then influenced by a force, which tries to move it through the magneticfield. In the AC induction motor the magnetic field is placed in the stationary part (stator). Theconductors influenced by the electromagnetic force are located in the rotor.The stator consists (usually) of 3 windings (phases) displaced 120 electrical degrees apart. When fedby a 3 phase alternating current they induce a current in the conductors of the rotor. The interaction ofthe magnetic field produced by the stator and the current carrying conductors in the rotor causes therotor to be 'dragged' round by the stator field.Applications include hoists, cranes conveyer belts, traction control, washing machines, HVACsystems.3 Phase Motor ControlThree Phase Synchronous AC Motor
Similar to the BLDC motor, the rotor of a permanent magnet synchronous AC motor consists ofpermanent magnets. The stator has 3 phase windings distributed sinusiodally as opposed to thesalient pole distribution found in a BLDC motor. The stator when energised by a 3 phase alternatingcurrent creates a synchronously rotating flux which causes the rotor to rotate synchronously with it.Due to the sinusoidal excitation of the windings the resultant torque generated by this motor is muchsmoother than that of the BLDC motor. Applications include compressors, pumps, fans, dishwashers,washing machines, servo controls.Brushed DC MotorThe stator contains two or more permanent magnet pole pieces. The rotor contains windingsconnected to the voltage supply via brushes and a mechanical commutator. The opposite polarities ofthe energised winding and the stator magnet are attracted and the rotor rotates until is aligned withthe stator. Just as the rotor reaches alignment, the brushes move across the commutator contactsand energise the next winding causing continuous rotation. The speed of the motor is proportional tothe voltage applied to it. Reversing the connections to the motor reverses the direction of rotation.Applications include toys, toothbrushes, shavers, cordless tools, small fans.BrushLess DC (BLDC) motorA DC brush type motor has a permanent magnet stator and a wound rotor. The configuration of abrushless motor is reversed, i.e. a permanent magnet rotor and a wound stator. Furthermore, thereare two types of brushless motors; the type that has an outer rotating magnet or the type that has aninner rotating magnet assembly. In a brushless DC motor the position of the coils (phases), withrespect to the permanent magnet field, are sensed and the current switched electronically(commutated) to the appropriate phases. Hall Effect sensors are typically used to sense the rotorposition. Otherwise, sensorless techniques are used. Applications include compressors, pumps, fans,dishwashers, washing machines, door openers, HVAC systems.
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Single Phase AC Motor

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