AC universal motor is mainly composed of stator rotor and bracket, stator is composed of convex pole core and excitation winding, rotor is composed of hidden pole core, armature winding, commutator and rotating shaft. A series circuit is formed between the excitation winding and the armature winding by a brush and a commutator.
In the supply of AC power, the principle of rotating torque can still be explained by the operation principle of DC motor.
When there is a current in the conductor, a magnetic field arises around the conductor, and the direction of the magnetic line depends on the current direction. Electric conductor into the magnetic field, the magnetic field and the magnetic field interaction, will make the conductor by a force F, and therefore produce movement, the conductor will move from the magnetic line to the magnetic line in the direction of the magnetic line, when two coil composed of opposite conductor into the magnetic field, the two sides of the coil is also under the force, the direction of the two force is opposite, torque.
When the coil turns in the magnetic field, the corresponding two coil edge, from one pole to another pole, because the magnetic field polarity has changed, will make the conductor by the direction of the force change, also change the direction of the torque, so that the coil turns in the opposite direction, so the coil can only swing back and forth around the central axis.
