DC motor (direct current machine) is a rotating motor which can convert DC electric energy into mechanical energy (DC motor) or mechanical energy into DC electric energy (DC generator). It is a motor that can realize the conversion of DC electric energy and mechanical energy to each other. When it is used as a motor, it is a DC motor, which converts electric energy into mechanical energy, and when it is used as a generator, it is a DC generator, which converts mechanical energy into electric energy.

composition structure

The structure of the DC motor shall consist of two parts of the stator and the rotor. The part of the stationary part of the direct current motor is called a stator, and the main function of the stator is to generate a magnetic field, and consists of a base, a main magnetic pole, a reversing pole, an end cover, a bearing and a brush device, and the like. The part of rotation at the time of operation is called the rotor, and the main function is to generate the electromagnetic torque and the induced electromotive force, which is the hub of the direct current motor for energy conversion, so it is commonly referred to as the armature, and is composed of a rotating shaft, an armature core, an armature winding, a commutator and a fan.

(1)main magnetic pole

The function of the main magnetic pole is to produce the air gap magnetic field. The main magnetic pole consists of two parts: the main magnetic pole core and the excitation winding. The core is usually pressed and riveted with 0.5mm~1.5mm thick silicon steel plate, which is divided into two parts: polar body and pole boot. The part of the upper excitation winding is called the polar body, and the widened part below is called the polar boot. The pole boot is wider than the polar body, which can not only adjust the distribution of magnetic field in the air gap, but also facilitate the fixed excitation winding. The excitation winding is made of insulated copper wire and is wrapped on the core of the main magnetic pole. The whole main magnetic pole is fastened to the machine seat with screws.

(2) commutation pole

The function of the commutation pole is to improve the commutation and reduce the commutation sparks that may occur between the brush and the commutator when the motor is running. It is generally installed between two adjacent main magnetic poles and is composed of the commutation pole core and the commutation pole winding. The commutation pole winding is made of insulated conductor and is wrapped on the core of the reversing pole, and the number of the commutation pole is equal to that of the main magnetic pole.

(3) seat

The housing of the motor stator is called the seat. There are two functions of the pedestal: one is to fix the main magnetic pole, the reversing pole and the end cover, and to act as the support and fixed function of the whole motor; the other is that the pedestal itself is also a part of the magnetic circuit, which forms the magnetic path between the magnetic poles, and the part through which the flux passes is called the yoke. In order to ensure that the seat has enough mechanical strength and good magnetic conductivity, it is usually made of steel castings or welded by steel plate.

(4) Brush device

Brush device is used to introduce or draw DC voltage and DC current. The brush device is composed of brush, brush grip, brush rod and brush holder. The brush is placed in the brush grip and pressed with spring so that there is a good sliding contact between the brush and the commutator, the brush grip is fixed on the brush rod, and the brush rod is mounted on the circular brush rod seat, which must be insulated from each other. The brush rod seat is mounted on the end cover or bearing inner cover, and the circumferential position can be adjusted and fixed after adjustment.

 rotor

(1) armature core

The armature core is the main part of the main magnetic circuit and is used to insert discharge armature windings. Generally, the armature core is made of 0.5mm thick silicon steel sheet, in order to reduce the Eddy current loss and magnetic lag loss caused by the armature iron core during the operation of the motor. The stacked core is fixed to the shaft or rotor support. The outer circle of the core has an armature slot, and the discharge pivoted winding is embedded in the slot.

(2) Armature winding

The function of armature winding is to produce electromagnetic torque and induction EMF. It is the key component of DC motor for energy conversion, so it is called armature. It is composed of many coils (hereinafter referred to as elements) connected according to a certain rule. The coils are wound with high strength lacquer wire or glass wire wrapped in flat copper wire. The coils of different coils are embedded in the armature slot in two layers, and the coil and core, as well as the upper and lower coil edges, must be properly insulated. In order to prevent centrifugal force from throwing the coil edge out of the slot, the slot is fixed with slot wedges. The end of the coil sticking out of the slot is tied with a thermosetting weft-free glass belt.

(3) commutator

In DC motor, the converter with brush can convert the external DC power supply into the alternating current in the armature coil, so that the direction of the electromagnetic torque is constant. In the DC generator, the commutator with brush can convert the alternating electromotive force generated by induction in the armature coil into the positive and negative electromotive force induced by the negative brush. in the DC generator, the alternating current EMF induced by the induction in the armature coil can be converted into the positive EMF and the DC EMF induced by the negative brush. The commutator is a cylinder made up of many commutators, which are insulated by mica chips.

(4) rotating shaft

Rotating shaft is used to support rotor rotation, and it shall have certain mechanical strength and rigidity, which is generally made of round steel.