ABB has come up with a new type of motor winding that eliminates
circulating bearing currents - a phenomenon that causes premature bearing
failure in inverter fed motors.
Experiments at the company's motor development and manufacturing site in
Finland showed that the problems were caused by asymmetric distribution
of high frequency currents in the motor.
The solution involves dividing up the winding in two equal parts, which
are both wired back to the drive end and non-drive end of the motor
before being routed to the centrally placed terminal box.
A US patent has already been granted for ABB's new winding configuration,
and a European patent is pending.