Electric carbon products (brushes for electric machines). Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Electric carbon products (brushes for electric machines). Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electricity for beginners

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This kind of products include brushes for electric machines, electrodes for arc furnaces, contact parts, etc. Electric coal products are made by pressing from the initial powdery masses, followed by firing.

The initial powdery masses are made up of a mixture of carbonaceous materials (graphite, soot, coke, anthracite, etc.), binders and plasticizers (coal and synthetic tars, pitches, etc.). In some powdered masses there is no binder.

Brushes for electric machines are graphite, carbon-graphite, electrographite, metal-graphite.

Graphite brushes are made from natural graphite without a binder (soft grades) and with a binder (hard grades). Graphite brushes are soft and cause little noise during operation.

Carbon-graphite brushes are made from graphite with the addition of other carbonaceous materials (coke, soot), with the introduction of binders. The brushes obtained after heat treatment are coated with a thin layer of copper (in an electrolytic bath). Carbon-graphite brushes have increased mechanical strength, hardness and low wear during operation.

Electrographite brushes are made from graphite and other carbonaceous materials (coke, soot), with the introduction of binders. After the first firing, the brushes are subjected to graphitization, i.e., annealing at a temperature of 2500-2800 ° C. Electrographitized brushes have increased mechanical strength, resistance to jerky load changes and are used at high circumferential speeds.

Metal-graphite brushes are made from a mixture of graphite and copper powders. Some of them introduce powders of lead, tin or silver. These brushes feature low resistivity, high current densities and low transient voltage drops.

Author: Smirnova L.N.

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