Carbon Brush Grade Choices for Electrical Motors
Carbon brush grades fall under four main categories based on the manufacturing procedures, the types of carbons and other ingredients. The types of brushes are: carbongraphite, electrographite, graphite and metal graphite.
Carbon graphite brushes for electrical motors are among the oldest carbon brush types. They are made of high strength material, but are generally limited to lower current densities on older, slower speed machines. High friction with this type of material makes it unsuitable for present day use on commutators.
Electrographitie Carbon Brushes
Strength and density distinguish electrographitic carbon motor brushes. This is due to the makeup of raw materials that go into making these brushes. The outcome is superior commutating ability, performance at high temperature/low humidity settings and as a result, longer life. Treatments can allow electrographitic materials to operate well in a variety of contaminated environments.
Graphite Carbon Brushes
Graphite brushes are layered with graphite bonded with resin to form a layered brush material. Their controlled filming and excellent riding qualities on both commutators and slip rings characterize these graphite brushes. The fast filming properties of graphite brushes is beneficial in protecting the commutator or slip ring during operation in contaminated atmospheres. Their low absorption and higher density are valuable in reducing commutator threading found in contaminated environments.
Metal Graphite Carbon Brushes
Metal graphite carbon brushes for electrical motors are often made from natural graphite and fine metal powders. Copper is the most common, but silver, tin and lead are sometimes used. Metal graphite brushes are ideal for many applications due to low resistivity. Metal graphite brushes are used on commutators of plating generators that have low voltage and high brush current densities. They operate on rings of wound rotor induction motors where high brush current densities are also found. Metal graphite brushes are used with grounding brushes because of their low contact drop.
Cross Reference for Replacement Carbon Motor Brushes
Your supplier may offer original OEM carbon brushes as well as their own private label lower-cost alternatives. Their carbon brushes, contactors and coils can often match the OEM product in fit, form, and function. Check to see if they have a Cross Reference tool on their company website.
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