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The main components and functions of DC motor

Date:2023-08-09   Author:XINDA MOTOR
A DC motor consists of a stator, a rotor and other components.
1. Stator
The stator of a DC motor is the part that generates the magnetic field of the motor, and consists of a machine base, main magnetic poles, excitation windings, and commutation poles.
1. Base
The frame of the DC motor is not only the shell of the motor, but also used as a protection and support structure, and is also a part of the magnetic circuit of the motor (that is, the yoke part).
2. Main pole
The function of the main pole is to generate a magnetic field, which is composed of the main pole core and the excitation winding.
The main pole core consists of two parts, the pole body and the pole shoe (also known as the pole shoe). The side near the rotor is called the pole shoe. The pole shoe is generally wider than the pole body to make the magnetic flux distribution under the pole even. When the rotor rotates, due to the movement of the slots and teeth relative to the magnetic poles, the magnetic density changes on the surface of the pole shoe, resulting in eddy current loss. In order to reduce this eddy current loss, the magnetic pole core is usually punched and laminated with thin steel plates with a thickness of 1 to 2 mm. , made with rivets. It is also made by laminating 0.5mm thick silicon steel sheets.
3. Excitation winding
The excitation winding is a concentrated winding, usually made of copper wire or aluminum wire on the winding machine according to the size of the model, and then put on the iron frame slightly larger than the main pole core, and the iron frame is then set on the main pole core Above, mica insulating paper and epoxy fiberglass laminates are used as good insulation between the winding and the iron frame, and finally treated by dipping paint. The entire main magnetic pole is fixed on the machine base with a screw, and when a direct current is passed into the excitation winding, the main magnetic flux is generated in the motor.
4. Commutation pole
In order to improve the commutation, most DC motors are also equipped with commutation poles, also known as intermediate poles, between the main magnetic poles. The commutation pole has a large air gap to the rotor, so the eddy current generated is small, so the iron core is mostly made of a whole piece of steel, and in large DC motors, it is also made of steel sheets.
The winding of the commutation pole is generally connected in series with the armature winding, and the current is relatively large. It is generally wound with round copper wire or flat copper wire with a large cross-section. The structure of the commutation pole is similar to that of the main magnetic pole.
Second, the rotor (ie armature)
The rotor is composed of iron core, winding, commutator, rotating shaft and fan blades. The rotor is an important part of energy conversion.
1. Armature core
The armature core is a cylinder with evenly distributed teeth and slots. In order to reduce hysteresis and eddy current loss, the armature core is generally made of laminated 0.5mm thick silicon steel sheets that are insulated from each other.
2. Armature winding
The main function of the armature winding is to generate induced potential and output or input current, so that the motor can realize energy conversion. The armature winding is usually made of insulated copper wire wound into a coil on the wire mold and then embedded in the iron core slot, and the two ends of each element of the winding are respectively connected with the corresponding commutator segments. In order to prevent the winding from flying out due to centrifugal force when the armature rotates, the notch is sealed with a slot wedge; the end protruding out of the slot is fastened to the winding support with epoxy phenolic non-woven glass ribbon or steel wire.
3. Commutator
The commutator acts as a commutator, and it is a cylinder made of many wedge-shaped commutation pieces (copper pieces) that are insulated from each other. There are many types of commutators. Metal sleeve commutators and plastic sleeve commutators are often used in small and medium-sized DC motors. Plastic sleeve commutators can save a lot of copper and mica, and simplify processing. craft.
3. Other components
1. Brush device
The commutator is connected to the external circuit through brushes. The electric brush is contained in the brush holder, and the brush holder is fixed on the brush rod insulated with it, and the brush rod is installed on the brush rod seat. The brush holder can move around the axis, so that the position of the brush on the commutator can be adjusted. After the position of the brush is adjusted, fix the brush rod seat on the end cover (the brush rod seat of a large motor is fixed on the frame), and no longer change it.
2. End cover
Generally made of cast iron, it has two parts, the front end cover and the rear end cover. The rear end cover is equipped with an observation window for checking the size of the brush sparks. The end cover is usually used as the support and mounting bearing of the rotor, but the bearings of large motors are installed on the bearing housing.