Characterisation and modelling of bearing current activity
Premature failures of bearings in electrical drive systems started to increase in the early 1990’s due to the introduction of the Insulated Gate Bipolar Transistor (IGBT). The converter modulation scheme, in combination with high voltage derivative, creates a high-frequent shaft voltage that drives a current through the bearing. This, together with discharge of energy stored in stray capacitances, result in development of damages such as micro-craters on the balls and fluting pattern on the raceways. The overall aim of the research in this project is to increase the electro-physical understanding of how bearing currents are initiated in a steel bearing in presence of a shaft voltage and understanding of the damages that these currents cause. The electrical behaviour and properties of a bearing at different operating points have been experimentally investigated and modelled.