Electrographites - Commutation & Collection (Carbon partially transformed into graphite by heating to temperatures in the range 2200°C to 2800°C)
- Biggest range of applications
- DC drives, & AC rings, etc.
- Current densities normally in the range 4 to 16Acm-2
- Surface speeds up to 50ms-1
Metal graphites - Mainly collection except for low voltage applications
Copper
- low voltage/collection of high current
- Current densities 12 to 30Acm-2
- Surface speeds up to 30ms-1
Silver
- low voltage with good signal integrity
- Current densities vary from almost zero to 30Acm-2
- Surface speeds up to 30ms-1
Natural graphites - Collection
- TA exciters with steel sliprings
- Current densities up to 12Acm-2
- Surface speeds up to 80ms-1
Resin bonded - Commutation
- High contact drop (poor commutation) or low current/temperature applications
- Current densities up to 8Acm-2
- Surface speeds up to 30ms-1
Metal impregnated - Commutation
- High strength/ high current requirements
- Current densities up to 30A/cm-2
- Surface speeds up to 40ms-1
Hard carbon & carbon graphites - Commutation
- 'Older applications’ or Difficult commutation
- Current densities up to 10Acm-2
- Surface speeds up to 30ms-1