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Description of the working principle of DC motor

The working principle of the DC motor is to change the alternating electromotive force generated in the armature coil by the commutation function of the commutator and the brush, so that it becomes the principle of the DC motor when it is taken out from the brush end.
The DC brush is not applied to the brush, and the armature is dragged by the prime mover to rotate counterclockwise at a constant speed. The magnetic lines under the magnetic poles of different polarities are cut on both sides of the coil, and the electromotive force is induced therein, and the direction of the electromotive force is determined by the right hand. determine. Since the armature rotates continuously, it is necessary to alternately cut the magnetic flux lines under the N and S poles by the coil sides ab and cd in the magnetic field, although the induced electromotive force in each coil side and the entire coil The direction is alternating. The induced electromotive force in the coil is an alternating electromotive force, and the electromotive force at the B and B terminals is the DC electromotive force (to be exact, it is a pulse-electromotive force with a constant direction). Because, during the rotation of the armature, no matter where the armature is turned, due to the commutation of the commutator with the brush, the electromotive force drawn by the brush A through the commutator is always in the side of the coil that cuts the N-pole magnetic line. The electromotive force, therefore, brush A always has a positive polarity. By the same token, the brush B always has a negative polarity, so the brush end can lead to a pulsed electromotive force with a constant direction but a varying size. If the number of coils under each pole is increased, the degree of vibration can be reduced, and the DC electromotive force can be obtained. This is how the DC motor works. It also shows that the sub DC motor is essentially an alternator with a commutator.
In terms of basic electromagnetic conditions, a DC motor can work either as a motor or as a generator, but only under different constraints. On the two brush ends of the DC motor, add DC voltage, input electric energy into the armature, mechanical energy output from the motor shaft, drag the production machinery, convert the electric energy into mechanical energy and become the electric motor, such as dragging the DC motor with the prime mover The armature, and the brush does not add DC voltage, the brush end can draw the DC electromotive force as a DC power source, can output electric energy, the motor converts the mechanical energy into electric energy and becomes the generator motor. The same motor can be used as an electric motor or as a generator. It is called the reversible principle in motor theory.

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