A US company has developed a quick-fit technology that diverts harmful shaft currents away from a motor’s bearings and safely to earth, protecting the bearings and extending their lives. Electro Static Technology’s Aegis SGR bearing protection ring is attached to a motor’s end bell in minutes using a conductive epoxy which eliminates the need to mark and drill holes in the motor.

The system (above) is based on a patented technology that EST has been selling since 2004 and claims is already used on around 150,000 motors worldwide. Unlike conventional earthing brushes, the maintenance-free rings are designed to operate without wear or friction for the life of the motor.

If the shafts of inverter-controlled motors are not earthed effectively, currents can discharge through the bearings, causing pitting and fluting damage to the bearing race walls. This can lead to noise, vibration and, ultimately, to bearing failure. There are other techniques for tackling the problem, including current-resistant bearings.