I noticed the superior choice would be a carbon based brush,however, is pure copper brush a bad choice?

I'm considering copper due to the lower resistance and higher current carrying capacity. I realized the coe. of friction for carbon brushes is indeed lower than copper, but if motors/generators used copper brushes for higher current capacity is that manageable?

I assume the friction is too great, generating excessive heat and wear.

  • 2
    Welding and galling may be a problem... – Ecnerwal May 24 '16 at 14:08
  • Are carbon brushes more forgiving of the momentary short between commutator segments than a copper brush might be? – Transistor May 24 '16 at 17:12

Under pressure and heat, copper smears. This will produce a layer of copper on the brushes which will short them out.

  • One could use an extremely thin(0.001m) graphite sheet to coat the two surface for full conductivity and avoiding such problems? – Pupil May 25 '16 at 23:34

Taken from wikipedia:

Early machines used brushes made from strands of copper wire to contact the surface of the commutator. However, these hard metal brushes tended to scratch and groove the smooth commutator segments, eventually requiring resurfacing of the commutator. As the copper brushes wore away, the dust and pieces of the brush could wedge between commutator segments, shorting them and reducing the efficiency of the device.

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