With their power density, modern, converter-fed three-phase drives are the frequent source of damages through spark or electroerosion in roller bearings.
Such damages occur for instance, when high-frequency currents flow through the rolling elements and contact surfaces within the paths. Such bearing currents are not readily measurable and can cause potential differences of more than 100 V with peak loads of up to 200 Amp.
Depending on the duration and energy density, considerable damages to the running path through to its complete failure might occur within a short period of time.
Experts recognise such damages for example by the appearance of melting craters rapidly increasing and deepening in a pulse-like way. Also, the lubricant changes its colour in many cases.
Due to the electrical discharge the material will be heated and can even melt at the surface. In that case, particles will break out and the structure of materials will change.
Bearing currents can be avoided in an elegant way by using current insulated roller bearings. Insulation occurs in the form of a ceramic layer at the outer ring and through the use of ceramic rolling elements (hybrid bearing). Current insulated bearings have the same outer dimensions as standard bearings which is the reason why they can be exchanged afterwards.
We have compiled and checked all data, but can not accept liability for any errors or omissions.