An Insight Into The Carbon Brush Grade Families

Carbon Brush Grade Functions

Carbon brushes are key components for mechanical devices to conduct electricity between the movable and stationary parts. It is important to understand the functionality of the brushes to use them appropriately. Carbon brushes are categorized into different grades based on the manufacturing process and the types of carbon and other elements used.

The four basic brush grade families include:

·         Carbon Graphite

·         Electrographites

·         Graphite

·         Metal Graphite

Carbon Graphite

Pioneers of this industry, this grade Carbon brushes are made of very strong materials with outstanding cleaning action. Carbon graphite brushes have low current densities 45 amps/in² (7 amps/cm2); hence these brushes are used on old and slow speed machines with maximum surface speeds around 4000 feet/minute (20.3 m/Sec). As these brushes output high friction, it does not fit in the recent day commutators, but are helpful as good contacts and base for metal-infused grades.

Electrographite

Electrographite brushes when baked over 2400°C is transformed into a graphite structure. For an excellent commutating capability and long life, the density, strength, hardness, and resistance are regulated with a specific mix of raw material composition and processing. High temperature removes pollutants, which makes the electrographite brushes abrasive-free. These brushes are normally porous enabling treatment using organic resins or inorganic materials. This makes the brush strong and lubricating increasing its life at high operating temperatures and low humidity.

This kind of treatment enables electrographite brushes to function in contaminated surroundings. Friction in electrographite brushes are introduced by a specific mix of raw material prior to graphitization and by treating the product with resins. These brushes can operate at 80 amps/in² (12.4 amps/cm2) continuously and surface speed of 7000 feet/minute (35.6 m/sec). There might be much bigger values amidst their functioning, which apply extensively to the industrial, transportation, mining and aerospace industries on both AC and DC machinery.

Graphite Brushes

Graphite made of natural or artificial graphite combined with resin or pitch to form a layered brush. These brushes comprise of ash, which makes them abrasive. Artificial graphite is not made of ash or does not comprise of the flaky structure as in the natural graphite.

The slip rings in the graphite Einhell carbon brushes comprise of filming and excellent riding qualities on both commutators, when they are at densities 45 to 65 amps/in² (7 to 10 amps/cm2). These brushes are not resistant, but high surface speeds are its best characteristics. When the brushes operate at contaminated environment, the commutator or slip ring is protected by the fast filming properties. Commutator threading occurs in contaminated atmosphere, which can be reduced due to low porosity and high density.

Metal Graphite Brushes

Metal graphite brushes are made of natural graphite and fine metal powders. The most common metal is copper followed by silver, tin, lead and other metals. Any such materials can be used. These brushes have low resistance and are ideal solutions for numerous applications. Metal graphite comes in handy for commutators such as generator plating when low and high-density collide with each other. These brushes are also used in induction motors with high brush current densities and for grounding brushes due to low contact drop.