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Should be negative wear large, previously read a good article
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Carbon brush and slip-ring working surface wear has two kinds: one is the pure mechanical wear; one is in the current under the action of the electrical wear and mechanical wear.
(1) a purely mechanical wear
Carbon brush and slip-ring surface contact, due to the spring pressure and elastic deformation reason, makes direct contact with each other embedded part. When the relative sliding, of course there is friction and wear. If the carbon particles are soft, toner is easily stick in the surfaces of the slip ring, the ring into a shiny stone mirror, brush grinding surface is smooth, the mechanical wear is small. But if the brushes are of poor quality, coarse hard, or even contain a few such as emery and hard particles, is bound to the ring surface scraping and cutting, so that the latter appear shiny metal or grain, grinding brush itself will also appear durum off after drew the track, which makes it big ( mechanical wear2) in the current under the action of the electrical wear and mechanical wear
In the current, not only the mechanical wear, and electrical wear. The electrical wear, is due to the high arc temperature and discharge of the role of factors such as the surface material, damage case. Because electrical wear affects the face, so it will have influence on the mechanical wear.
Due to the current through the brush and slip ring contact surface, and the conductive part is changing ceaselessly, current density is big, make some point temperature is very high; and due to the high temperature arc, will make both sides of polar partial melting, shedding, metal into metal vapor, carbon brush structure loose, affected by oxidative corrosion and exfoliation, the electrical wear performance of. However, the different polarity, wear is not the same. Under the arc action, an anode (positive electrode) surface of local hot and steaming out" metal vapor", so that the anode surface erosion, which is called" the anode cathode (negative electrode ); evaporation" by positive ion impact and the high temperature of the surface of the cathode electron emission, which is destroyed, it is called" cathode powder". As the anode and cathode evaporation pulverization effect, carbon brush and slip-ring due to the current direction is different there will be differences in polarity.
When the current flow to the ring by a carbon brush, the brush is positive, the slip ring is negative, then the result is: the brush surface of small degree of carbon, graphite anode evaporation, ion migration to the surfaces of the slip ring, brush electrical wear. Slip ring surface with slight cathode powder, and attachment of carbon, graphite, a lubrication, shiny mirror. As a result of slip ring surfaces smooth, mechanical wear small.
1 h when the current from the slip ring to brush, the brush is negative, the slip ring is positive, then the result is: Brush surface occurs on cathode powder, small electrical wear. Slip ring surfaces anode evaporation. A lot of metal evaporation, so that its surface erosion is serious, at the same time, these metal particles are also attached to the carbon brush abrasion on the surface, which in turn will make the surface of the commutator wear serious, streak. In this case, the slip ring is a metal surface roughness, surface light, mechanical wear. ( P ( x9Q7
In general, when the brush is positive: Brush electrical wear, mechanical wear slightly, the slip ring electrical wear and abrasion is small; when the brush is negative, the brush electrical wear small, mechanical wear, slip ring electrical wear, mechanical wear are large. U6O' y F" $ }%,
In order to make wear uniform, for the ring, because the ring current by a carbon brush to brush slip ring slip ring, positive, negative, it is ring wear small; similarly, the negative ring wear, so the two ring polarity often exchange. The power plant overhaul, often switching is negative ring connection cable. This is the truth.
When no current, brush grinding surface of coarse particles is easy to embed a slip ring surface, due to mechanical wear, or even cause friction vibration. When current flows through it, brush grinding surface of coarse particles is best, flour, dip in the surface, reducing friction, so that the mechanical abrasion, and the brush run very calm. So, in the normal current situation, current to reduce mechanical wear and benefits. However, if the current density is too large, then the anode evaporate serious, will make the electrical abrasion. While the electrical wear is exacerbated, the slip ring surface roughening, carbon brush is attached to the surface of metal powder, mechanical loss will increase, so the brush current density due to a limit. " E. a
As for the spring pressure, to wear also has an effect. Pressure is too small, the carbon brush and slip ring surface contact are not stable, easy to cause the arc, to increase electrical wear. The pressure is too large, the brush surface of hard particles on the surfaces of the slip ring scraping and cutting of serious, and the mechanical wear increase. Therefore, the pressure of the spring to be moderate.
by: becky
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