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The Basic Structure of DC Motor

By Cayla | Published on Sep 14,2015
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DC motor consists of a stationary stator and a rotating rotor , there is a certain size gap between the stator and the rotor (called air gap).

1. Stator:

The roles of DC motor stator playing are generating magnetic field and used as a mechanical support of the motor. Mainly composed of the base, the main pole, com-mutating pole, brush and other components.

1) Base: Base plays role in mechanical support and Permeability magnetic circuit. It is used as the motor housing of all parts installation, but also the Guide magnet yoke connect the magnetic poles. Base is usually cast steel, there is also plate welded bases.

2) Main pole: The main magnetic pole is a magnet, has the main poles core and the main pole coils two parts. Main pole core generally uses 1-1.5mm thick laminated steel sheet after punching then rivets clench into a whole. Small motor main pole coil with insulated copper (or aluminum) around the system, and medium-sized motor main pole coils flatted with copper wire, and insulated, then sets out the main pole cores. The entire main magnetic poles are fixed to inner wall of base with screws.

3) Commutation pole: Commutation pole is also known as additional pole, which is mounted between the two main poles, used to improve the DC motor commutation. Commutation pole is composed of commutation pole core and commutation pole winding. Most commutation pole core is processed with a single piece of steel. But in a larger power supply rectifier motor, in order to better improve the motor commutation, commutation pole cores also use laminated structure. Commutation pole coil is also made of round copper wire or flat copper wire that is the same as the main pole coils, after insulation, setting in the commutation pole core, finally the commutation pole fixed in the housing inner wall by screws.

4) Brush gear: Brush is used to connect rotating armature winding and external circuit by sliding contact with the brushes and commutator surface. Brush gear generally consists of the brush, brush holder, brush bar, stems seat and other components. Generally brush is presses by graphite. Brush is put in brush holder, with the spring-loaded on the commutator, brush holder is fixed to the brush rod, brush lever is mounted on stems seat, thus becoming an integral part.

2. Rotor:

Rotor is also known as armature, mainly composed of shaft, armature core, armature winding and commutator etc.

1) Shaft: The rotating shaft is used to transmit torque, generally made of alloy steel.

2) Armature core: Armature core is one part of the motor magnetic circuit, but also a part withstanding the electromagnetic force. When the armature is rotating in a magnetic field, eddy current and hysteresis losses generated in the armature core. In order to reduce the impact of these losses, the armature core is usually laminated with 0.5mm thick electrical steel sheet, the armature core is fixed to the rotor stand or shaft. Armature core laminations are evenly distributed grooves along the outer core, embedding the armature coil in the groove.

3) Armature winding: The role of the armature winding is to produce EMF and generate torque through electromagnetic currents, thus achieving the mechanical energy and electrical energy conversion. It is a major part of the DC motor circuit. Armature windings are usually circular or rectangular cross-section of the wire around the system, then according to the certain rules embed into the armature slot, must be properly insulated between the upper and lower armature windings and core. To prevent the centrifugal force will throw winding outside the tank, at notch, slot wedges should be compressed by winding. Winding terminating portions extending outside the tank is tied with no latitude glass ribbon. Winding ends press certain rules embedded into the commutator increased steel sheet tank, and is welded by soldering or welding.

4) Commutator: Commutator is used for mechanical rectification. That is in the DC motor, a DC current is applied against it into alternating current in windings; and in the DC generator, ac potential in windings is rectified into the DC potential across brush. Commutator commutator segments are composed of many commutation. Between sheets, it’s insulated by mica sheet. One end of the commutator segments increased chip is called commutator riser, it is used to connect the ends of the armature winding. The riser bottom is made to dovetail. Using commutator hub, V-shaped pressure ring and screw the commutator pressure ring, mica fastened as a whole. In the segments and the commutator sleeve, with V-shaped pressure ring between mica insulating ring, and finally press commutator mounted on the shaft.


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