Working Principle Of DC Motor

A ring permanent magnet is fixed inside the DC motor. The current generates ampere force through the coil on the rotor. When the coil on the rotor is parallel to the magnetic field, the direction of the magnetic field will change. Therefore, at this time, the brush at the end of the rotor contacts with the conversion plate alternately, so the direction of the current on the coil will also change, and the direction of the Lorentz force generated will not change, so the motor can rotate in one direction.

The working principle of the DC generator is that the alternating electromotive force induced in the armature coil is changed into the DC electromotive force when it is led out from the brush end by the commutator in cooperation with the commutation of the brush.

The direction of the induced electromotive force shall be determined according to the right-hand rule (the magnetic induction line points to the palm of the hand, the thumb points to the moving direction of the conductor, and the direction of the other four fingers is the direction of the induced electromotive force in the conductor).

The direction of force on the conductor is determined by the left-hand rule. This pair of electromagnetic forces forms a torque acting on the armature, which is called electromagnetic torque in rotating electrical machines. The direction of the torque is counterclockwise, attempting to make the armature rotate counterclockwise. If this electromagnetic torque can overcome the resistance torque on the armature (such as resistance torque caused by friction and other load torques), the armature can rotate in a counterclockwise direction.