brush is a device that streams between stationary wires and moving parts, most often in a rotating shaft. Typical applications include electric motors, alternators and electric generators.
Video Brush (electric)
Etimologi
For certain types of electric motors or generators that function, the rotor coils must be connected to complete the electrical circuit. Initially this is done by applying a copper or brass commutator or 'slip ring to the shaft, with a spring that presses the brush wire bracket' into the current-carrying ring. Such brushes give a bad turn as they move from one commutator segment to the next. The remedy is the introduction of a 'high resistance brush' made of graphite (sometimes with additional copper). Although the resistance is on the order of tens of milliohms, they have a high enough resistance to provide a gradual shift of current from one commutator segment to the next. The term brush is still used. Because the brush is worn out, they can be replaced in products intended to allow maintenance.
Metal fiber brushes are currently being developed. They may have advantages over current brush technology, but have not seen a broad implementation.
Maps Brush (electric)
Manufacturing process
Mixing components
The exact composition of the brush depends on the application. Graphite/carbonate powder is generally used. Copper is used for better conductance (rarely for air conditioning applications and not for automotive fuel pumps running on carbon commutators). To maximize electrical conductivity and green power, very dendritic (electrolytic) copper powders are used. Binders, mostly resins or phenol or other clays, are mixed so the powder holds its shape when compacted. Other additives include metal powders, and solid lubricants such as MoS 2 , WS 2 . Much knowledge and research is needed to define a brush mixture for each application or motor.
Compacting the mixture
Brush compounds are compacted in a tool consisting of upper and lower blows and die, at mechanical or hydraulic presses. In this step, depending on the next process, the copper wire (called the shunt wire) can be inserted automatically through the hole at the top of the blow and fitted into the brush block pressed by the pressed powder. This operation, called "tamping", is usually done using electrolytic copper powders, possibly with a silver lining for some high performance applications. After this process, the brush is still very fragile and in professional jargon is called 'green brush'.
Firing the green brush
Next follows the heat treatment of a "green brush" beneath the artificial atmosphere (usually hydrogen and nitrogen). Temperatures range up to 1200 ° C. This process is called sintering or burning. During sintering, the binder either burns or carbonizes and forms a crystal structure between carbon, copper and other additives. Baking is followed by graphitization (heat treatment). The heat treatment is altered by specified temperature curves for each material mixture. In addition to the mixed composition, the temperature curve used is the second "secret" of any brush manufacturer. After heat treatment, the brush structure is modified in a way that makes brush copying almost impossible for a competing company.
Secondary operation
Sintering causes the brush to shrink and bend. They must be ground into a net. Some companies use additional treatment to make brushes more durable by methods such as surface impregnation that runs with special oils, resins and greases.
The manufacture of carbon brushes requires an in-depth knowledge of materials and experience in mixed compositions. Very small changes in the contents of the brush with only a few percent of the weight of the component can significantly change the brush properties of the application. There are only a handful of brush-developing companies in the world, most of which specialize in certain types of brushes.
Carbon brush is one of the cheapest parts in electric motors. On the other hand, they are usually the key parts that provide durability ("life time") and performance for the motor they are used. Their production requires very high attention to quality control and production process control throughout the steps of the production process.
Liquid metal brush
From time to time the use of molten metal to make contact is investigated. Weaknesses to this approach include the need to contain molten metal (because it is usually toxic or corrosive) and loss of power from induction and turbulence.
See also
- Commutator (electricity)
- Slip ring
References
Source of the article : Wikipedia
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