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§ Carry load current from / to rotating parts
§ Assists the commutation process
Electro – Graphite:
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Ø Improved brush life Ø High thermal & electrical conductivity Ø Improved surface film formation Ø Provides low humidity protection Ø Allows high temperature operation Ø Reduces copper drag Ø Minimizes commutator wear Ø Works in contaminated atmospheres Ø Reduces friction |
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Graphite:
Ø High electrical resistance
Ø Very good commutation
Ø Self – lubricant
Ø Low temperature
Metal – Graphite:
Ø High current density
Ø Very low contact drop
Ø Very low resistivity
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Ø Indispensable for proper brush operation Ø Guide & force the brush for intimate commutator contact Ø Provide an unobstructed channel, compensating commutator irregularity |
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Ø Highest form – stability & rotational precision under very hard conditions Ø High operating temperature & speed allowed Ø Insensitive to external vibrations Ø Good thermal conductivity Ø Excellent dielectric properties Ø High insulating resistance over the whole temperature range |
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