1. Stator
The main function of the stator is to generate a magnetic field and as a mechanical support of the motor, which is composed of the main magnetic pole, the reversing magnetic pole, the frame and the end cover, and the brush device.
(1) Main magnetic pole
The main magnetic pole is used to generate the main magnetic field. The main magnetic pole of most DC motors does not use a permanent magnet, but the field is established by the field winding through the DC current. The main magnetic pole is composed of an iron core and winding, the iron core is made of a low carbon steel plate with a thickness of 0.5~1.5 mm, and is riveted tightly after being folded. The expanded part of the air gap is called the pole shoe, and the pole shoe supports the exciting winding, so that the air gap magnetic flux has a better wave distribution. The exciting winding is wound with insulated copper wire, impregnated by insulating paint, and then placed on the magnetic pole core. The main magnetic pole N and S are arranged alternately, evenly distributed and fixed on the inner ring of the frame with screws.
(2) Commutator pole
The commutator pole is used to improve the commutator of the DC motor, also known as the additional pole, composed of the iron core and the commutator pole winding set on the iron core, the iron core is commonly made of whole steel or thick steel plate, the commutator pole winding with the armature winding series, the number of the commutator pole is generally the same as the number of the main magnetic pole or half, the air gap between the commutator pole and the armature can be adjusted. The commutator pole can not be installed in the DC motor with very small power.
Engine base
The frame is both the shell of the motor and a part of the magnetic circuit of the motor, generally cast with low carbon steel or welded with steel plates, and the two ends of the frame have end covers. The front and rear end covers of small and medium-sized motors are equipped with bearings for supporting the rotating shaft. Large motors use pedestal plain bearings.
(4) Brush device
The function of the brush device is to connect the armature winding of the rotating part with the external circuit, and lead the electromotive force and current of the armature winding to the load or power supply of the external circuit. The brush device is composed of a brush, a brush socket, a brush holder and a bus bar, etc., the brush is generally made of graphite and copper powder pressed and calcined, the brush is placed in the brush grip, and the spring presses it on the surface of the commutator. The number of brush rods is generally equal to the number of main magnetic poles.
2. Rotor
The rotor of DC motor is also called armature, which is composed of iron core, winding, commutator and cooling fan.
(1) Iron core
The armature core is used to form the magnetic circuit of the motor and to insert the armature winding. In order to reduce the loss of the core, it is usually stacked with 0.35mm or 0.5mm thick silicon steel sheets coated with insulating paint. In order to enhance cooling, the armature core of the small-capacity motor has an axial ventilation hole, and the large-capacity motor has a radial ventilation ditch.
(2) Winding
The role of armature winding is to generate induced electromotive force and electromagnetic torque, so as to convert electrical energy into mechanical energy. The armature winding is made of insulated copper wire, and then embedded in the armature iron core groove, the lead end of the winding is connected with the commutator sheet according to a certain rule, the groove part of the winding is compressed with an insulated groove wedge, and the end is tied with a glass ribbon.
(3) Commutator
The commutator is a key component of DC motor, which converts the AC electromotive force inside the armature winding into the DC electromotive force between the brushes. The commutator is composed of mutually insulated commutator pieces with a circular appearance. The reversing sheet is made of hard electrolytic copper, the changing pad is insulated with 0.4-1.0mm thick mica, the end of the whole cylinder is tightened with a V-shaped pressure ring, and the end of the changing photo and the V-shaped pressure ring are also insulated with mica, and the end of each reversing sheet has a protrusive raising sheet, which is used to connect with the winding lead end.
