When selecting a brush grade compatible with reactive gas atmosphere, there are many aspects thatmust be considered. We studied the effects of ambient gas (Cl
2, SO
2, H
2S) on brush-Cu slip ring contact. Resalts obtained are as follows.
(1) When a highly concentrated Chlorine gas-air mixture was passed by brush slip ring contact, the contact voltage drop of positive brush (motor notation) increased rapidly, while the contact voltagedrop of negative brush decreased gradually and the negative brushes started to pick up copper withinabout an honr.
(2) Considering the effect of brush grade on the result of above experiment, it isdesirable to applynatural graphite grade or coke type electrographite grade brush in chlorine gas atmosphere.
(3) It seems that chlorine attacks copper slip ring, forms heavy porous film on slip ring, and thefilm absorbs water vapour.
(4) It is concluded that the anomalous change of the contact voltage drop of positive brush in the presense of chlorine gas is due to the film formation on ring, and the copper picking of negative brush is owing to the electrolytic phenomena on brush slip ring contact.
(5) The behauiour of brush slip ring contact characteristics in sulphur dioxde or hydrogen sulphide atmosphere, looks alike to that of chlorine, but it should be noted that the effects of brush grade on the brush slip ring contact are not clear.
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