New Silver Graphite Grade Excels in Grounding Applications

The function of a carbon brush on power ring vs. a grounding ring is significantly different!

Many customers use copper graphite for power rings and use similar copper graphite grades for grounding rings. This typically results in grooving of the ground rings. The function of the carbon brush on power and ground slip ring is significantly different. This is where Helwig’s silver graphite grade K297 excels.

This grade was specifically designed for grounding applications and is becoming popular in the wind turbine market.

The low temperature and low relative humidity where many of these wind turbines are installed presents challenging operating conditions. Lack of moisture prevents the good film or patina formation that is needed on the ring to lower the wear. If a similar grade to the power rings is applied on the ground ring it typically results in following issues:

• Grooving / wear of the ring
• Excessive wear and /or dusting of the brushes
• Photographing of the brush face on the ring surface

  

  Excessive Wear

  

  Grooving of the ring

  

  Photographing of the brush face on the ring surface

  
  

Ideally, before installing new silver graphite grade K297 brushes the contact surface is cleaned for a fair test. The surface of ground rings can be rough or grooved from previous misapplication of carbon grades, therefore there is a need for a grade that rides the ring better. The special ingredients in K297 allow the brush to maintain good contact which is essential for grounding applications.

Additionally, independent testing has concluded that, both electrically and mechanically, grade K297 should give at par or better performance on a bronze contact surface than standard stainless-steel material, where it is already approved.

Please also note that along with the wind turbine grounding applications, this grade is successful in high speed turbine applications for grounding.

Nitin Kulkarni

VP Engineering and Business Development