Summary:...
Carbon brush motors provide high speed and high torque, are easy to run, and are generally inexpensive. However, there is one characteristic that is generally regarded as a defect, and that is the loss of carbon brushes. This requires frequent maintenance and downtime. And, in extreme cases, this will cause the motor to fail.
Through the use of commutator and carbon brushes (attached to the armature of the motor), the carbon brush motor performs mechanical commutation. The carbon brushes are connected to the power source, and the commutator is composed of separate parts connected to different rotor windings. As the motor runs, the carbon brushes contact different parts of the commutator, which energize the windings in a specific order. This creates a dynamic magnetic field that causes the rotor to rotate differently, and its stages are attached to the opposite poles of the stator.
The mechanical friction between the carbon brush and the commutator, as well as electrical erosion, will inevitably cause the loss of the carbon brush. However, although carbon brushes do need to be replaced periodically, there are several ways to extend life and reduce maintenance cost requirements.
Choose the right carbon brush material
Most manufacturers divide carbon brushes into the following five categories: carbon, carbon-graphite, graphite, electric graphite and metallic graphite. Traditionally, carbon brushes are composed of carbon-graphite. However, new materials can provide electronic features that extend the life of carbon brushes. For example, electric graphite carbon brushes have a low resistance and can tolerate higher temperatures than carbon-graphite. Metal graphite carbon brushes have a voltage drop, which makes them very suitable for low voltage applications. But in terms of lower speed applications, and in terms of newer options, graphite carbon brushes are still cheap.
Carbon brush grade is also important
In addition to carbon brush materials, the selection of carbon brush grades also has a major influence on the life of carbon brushes. The carbon brush grade shows the mechanical and electronic properties of the carbon brush, such as current density, hardness, and maximum pressure. If the carbon brush grade cannot meet the application conditions, then the rapid damage of the carbon brush seems inevitable.
In the carbon brush DC motor, a protective film of copper oxide and graphite is formed on the commutator. This film is formed by the interaction of carbon dust on the carbon brush, copper on the commutator, and humidity. (High-altitude application scenarios require special carbon brushes that can tolerate low humidity or are doped with other materials to compensate for low humidity). The carbon brush grade affects the formation of the protective layer, which in turn helps to avoid arcs and damaging sparks.
Check installation
The spring facilitates proper contact between the carbon brush and the commutator. In order to maintain good current flow, it is very important that all springs have equal spring pressure. However, as the spring is lost, the contact begins to decrease and the distribution of current between the carbon brushes begins to become unequal. Because it is very important to check the spring tension with a pressure gauge regularly.
In addition, each carbon brush can be embedded in an ink cartridge with a torsion spring. The torsion spring can limit the stroke of the carbon brush and ensure that the proper pressure can be maintained between Tan Shuang and the commutator. Although the ink cartridges have been installed, it is still very important to confirm that the ink cartridges and carbon brushes are properly installed. In every installation scenario, if the commutator and carbon brush contact is not maintained, sparks will be generated.
Avoid or remove pollution
The particles from the carbon brushes and commutator can provide a protective film. But too many particles, whether from the environment or the component itself, will interfere with the carbon brush contact and cause fatal damage to the carbon brush and commutator. Periodic cleaning of carbon brushes and commutators can avoid these problems.
Regarding silicone contamination, there is one item that needs special attention. Silicone can cause rapid damage to the carbon brushes. Because it is very important to avoid the use of silicone-based tapes or sealants.
EN
