DC electric motor: device, operation, application

The work of the aggregate considered in this article depends entirely on the phenomenon of electromagnetic induction. This is the basic principle of the DC motor. It is generally known that a force placed on a conductor with a current passing through it into the zone of a magnetic field is acted upon by a force that can be determined in accordance with the Left Hand Rule: F = B * I * L, where I is the electric current, B is the field induction; L is the calculated length. Crossing the magnetic lines of force, the conductor acquires an electromotive force, which, with respect to the flow of current, is directed against it, but is called reverse or counter-acting. The DC motor recycles the power into a mechanical form of energy, but also partially spends it on heating.

At superficial consideration of the mechanical device of the unit it is possible to notice the following: the composition of the DC motor is relatively simple, it is represented by an inductor and an armature, which are insulated by an air gap.

The inductor creates an immovable magnetic field of the machine and, in turn, consists of a bed, poles (main and additional). The poles are attached to the frame, and the substrate itself participates in the magnetic circuit of the installation. The main poles contain excitation windings that create a magnetic field, and additional poles contain a coil to improve the connection.

The DC motor is equipped with an armature made of separate sheets, a wire coil and a manifold (a copper-plated cylinder attached to the shaft ). The current is removed by means of brushes. They are fixed and held in a certain position, which provides the required force of pressing on the collector surface.

During operation, the DC motor moves the brushes over the surface of the reversing manifold in such a way that they constantly move from one plate to the other. This is how the parallel sections of the armature coil switch and the current in them changes. The process, as well as the phenomena associated with it, is called commutation. EMF causes an additional current, which has an uneven distribution of energy density on the surface of the brushes. This is the main cause of the arcing of the collector (the intensity of this phenomenon is estimated by the quality of commutation and gradation of its degrees is determined).

The DC electric motor is capable of undergoing excitation - creating in it a magnetic field necessary for the operation of the device. They are divided into four groups (according to the method of excitation):

• Independent, in which the winding is powered by a third-party direct current source.
• Parallel - the winding is connected in parallel to the source of the armature coil.
• Serial - enabled sequentially.
• Mixed type (with series and parallel excitation coils).

At the first moment of the launch, the anchor is stationary and the voltage in it is zero. The resistance is small, so the initial current can be 10-20 times higher than the rated current. To ensure smooth start-up, a stepped rheostat is used, the resistance value of which is selected based on the possible starting current of the motor.