Shaft grounding makes mining cutter more reliable

A dredge mine in Western Africa had suffered repeated bearing failures on its 2 MW cutter motor. The bearings showed fluting damage – the hallmark of electrical bearing damage from VFD control. This damage is caused by stray voltage produced by the drive on the motor shaft. A common solution is to ground the shaft to dissipate the stray voltage. So the mine installed carbon shaft grounding brushes, but failures continued. The grounding brushes also required frequent maintenance to keep the springs from jamming in the sandy environment.

In early 2025, an AEGIS PRO Series ring was installed on the cutter motor, as well as an AEGIS HFGS, a braided grounding strap that helps ensure stray current a path to ground. The AEGIS Pro Shaft Grounding Ring surrounds the motor shaft with hundreds of thousands, up to millions, of conductive microfibres which are able to bleed off stray voltage from VFD control.

A year on, the mine stakeholders remain happy with the system's performance – so much so that it is installing additional PRO rings and grounding straps on other equipment.

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This article appeared in Renew magazine. To read more or request your personal digital or print edition of Renew, click here.