According to its structure, the Brush Holder can include the followings:
- The Brush-Box type: the carbon brush is installed in the box-styled structure with its compact structure, reliable locating and wide applications.
- The Boom type: the carbon brush is pressured through its elastic arm with its relative simple structure.
According to its materials, the brush holder is generally designed with the followings:
- Copper casting: excellent electric conductivity to suit for its conductive parts;
- Aluminum casting: with lighter quality and excellent heat dissipation;
- Other synthetic materials: suitable for part of the insulated or auxiliary structures;
If selecting the materials, the engineer should fully consider the following factors, including anti-corrosion, heat dissipation, electric conductivity and its mechanic strength.
The regular maintenance of the Brush Holder
In spite of its small volume, the brush holder is regarded as one of the quick-wear part in the motor with the following problems in its long period of the operation:
- The downward or unbalanced spring pressure: owing to its aged spring or downward pressure after related fatigue, the carbon brush will be caused ineffective contact with its flaring up with heat.
- Worn brush box and bigger gap: owing to swaying carbon brush in the brush box, its contact stability will be directly affected.
- Unperpendicular brush holder and unsuitable installation: can lead to jam fault or eccentric wear of the carbon brush.
- Oxidation and corrosion: owing to humid environment or large amounts of its powder, the surface of the brush holder will be rusty and corrosive to affect its structure and conductivity.
Maintenance suggestion: regularly check the wear degree of the carbon brush and replace it timely if needed with the same lot and type. If necessary, the carbon brush should be replaced to a scale (For large-scaled motor, carbon brush can be replaced with its frequency of 20% per time with 1-2 week gradual substitution.) Pay attention to avoid mixing the old and the new together to cause unbalanced current distribution. Meanwhile, check the spring pressure and the gap of the brush holder as well as keep clean.
The applications of the brush holder
The brush holder can be widely applied on the equipment with its sliding current conductivity.
- DC motor with the brush: electric tools, toys, electrocar, starting dynamo of the automobile.
- The motor generator: for excitation system in thermal power generator, hydroelectric generator and wind power generator, the current can be transmitted into its rotator through the brush and the slip ring.
- wound-rotor asynchronous motor: through the resistance switched in the rotor circuit by the brush, the motor can be started or adjust its speed.
- Synchronous motor: exciting current can be transmitted into the rotor winding through the brush and the slip ring.
We can say that where there is a carbon brush there is a brush holder.
In conclusion, in spite of its unimpressive and hidden component in the motor, the brush holder acts as its key responsibilities for firm holding the carbon brush and pressurized conductivity.
Throng its brush-box locating and spring pressurization, the carbon brush can stable slide on high-speed commutator or slip ring, leading to the current that can be reliably transmitted into its rotating side from its static side.
We can say a one-sentence conclusion that the brush holder can be considered as a hand that can firmly hold the carbon brush in the motor with its stability, balanced forces, leading to the motor that can smoothly and solidly operate. So, when you use the electric tool, starting the automobile or seeing the slowly rotating windmill, you can think of that small but silent-working component.
