Brushes of the electric motor: purpose, types, replacement

The motor collector assembly is necessary to transmit electricity to the armature windings. Since the armature generates rotary motion during operation, the transmission is carried out through a special contact. For the organization of a rolling contact in all household and industrial engines, metal plates are not used. This is due to high speed, in which the friction of the metal on the metal would produce additional heating of the working surface and rapid production of the collector. Therefore, graphite or coal was chosen as the contact. He got the name - an electric brush.

Brushes of the electric motor

Contact sliding type, designed to lead and drain electricity on the collectors or ring contacts of all types of electric machines (electric motors and generators), was called the electric brush.

Brushes of the electric motor are produced both with conductors made of metal, and without them. Fastening of a wire in a brush carry out a method flaring, впрессовки or by means of soldering. Brush current generators come in the following brands:

• IPSH - a special type of wire stranded, made of copper wire;
• ПЩ - flexible type of a wire of copper wire weaving;
• PBS - universal wire with increased flexibility.

The contact wire is provided on the lead-in wire. With their help, the wire is fixed with a bolt of the brush holder. The tips are fork, flange, double and plate type.

Types of brushes

There are several classes of brushes that satisfy different switching conditions:

• Graphite brushes. They are made on the basis of graphite with the addition of filler in the form of soot and other substances. Brushes for switching light degree in generators and engines are intended. Available grades EG61A and G20.
• Coal-graphite type. Brushes of low strength for small mechanical loads. Brands G21, G22.
• Electrographic type. Brushes of increased mechanical strength, saturated with carbon. Perform medium-complexity commutation. Withstand large current loads. There are brands EG2A, EG74, EG14, EG4, EG841.
• Metal-graphite type (copper-graphite brushes for electric motors). The main component of the brush is copper, tin and graphite powder. To them there are different fillers. Brushes have high strength, do not pass gas and liquid medium. Applicable in high and medium complexity switching conditions. Provide the operation of low voltage generators. The brands have MG, MGS, MGS 5, MGS 20, MGS 51, MGSOA, MGSO, MGO1M, M1A, M1.

Brush contacts described are applicable in industry, brushes of G33MI, G33, G30, G31 brands are produced for household equipment.

Brush contact selection

The most important when selecting brushes of the electric motor is to know the parameters of the produced brushes. In addition to geometric dimensions, the new brush should match the graphite grade, type and cross-section of the wire. It is not necessary to take the same brand as the original, but the hardness of the brush motor and the operating modes must match. The thickness of the wire should not be less than the original, and the flexibility to match. The main mistakes in the selection of brush contact:

• Installation of a harder graphite contact to where the softer ones were used. The result can be rapid wear of the collector.
• Installation of "universal" brushes everywhere. This may interfere with the operation of the device.
• Orientation when buying a brush for marking graphite on the side of an old motor brush. Graphite marking is not a marking of contact parameters!

Why Brushes Are Sparkling

The spark of brushes sliding along the collector is natural, because at the time of the transition from one lamella to another, an arc micro-discharge occurs. With the proper functioning of the engine, serviceability and compliance of all elements, it is barely perceptible to the eye. But if the brush of the electric motor strongly sparkles, the reason speaks about malfunctions in work. Ignoring this process is fraught with failure of the anchor.

The reasons for which spark brushes are:

• Formation of deposit or contamination on the collector. Perhaps with prolonged engine operation without maintenance, a thin film of carbon formed on the collector's contacts. It has an increased resistance, which leads to sparking. You can correct the problem by treating the collector with sandpaper of zero grain size (in the direction the brushes rotate).
• Closing adjacent collector contacts with dust from graphite or fine copper powder. In this case, the currents in the circuits increase, which leads to strong sparking. Jumper should be carefully removed with a sharp object.
• Wrong selection of brush parameters. As a result of the discrepancy between the resistance of the contacts, there will also be sparks on the collector. It is necessary to replace graphite brushes, based on the technical documentation of the engine.
• Brush making.
• Interchannel closure in the armature windings. Check the anchor and replace in case of malfunction.

Replacement of motor brushes

Change the brush is necessary when the working part is not less than a third, and also follow the rules:

• Select brushes that match the parameters of the previous ones.
• Perform a visual inspection of the collector and cleaning if necessary.
• If the working surface of the brushes has a bevel, do not confuse its location.
• Give the brushes time to grind, including the motor without loads, and then remove the lapping dust from the manifold.

Conclusion

In addition to all the above measures for the care of brushes, there are also special lubricants of the collector unit. They allow to reduce the mechanical load on the contact and prevent the formation of carbon deposits.