Open AccessAnalytical determination of the end-winding portion of the winding-to-rotor capacitance for the prediction of bearing voltage in electrical machines
Author(s) -
Jan Ole Stockbrügger,
Bernd Ponick
Publication year - 2020
Publication title -
electrical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.35
H-Index - 35
eISSN - 1432-0487
pISSN - 0948-7921
DOI - 10.1007/s00202-020-01046-y
Subject(s) - rotor (electric) , capacitance , voltage , electrical engineering , bearing (navigation) , materials science , common mode signal , engineering , control theory (sociology) , mechanics , physics , computer science , electrode , control (management) , quantum mechanics , astronomy , artificial intelligence , digital signal processing , analog signal
The number of inverter-fed motors is increasing due to the good controllability of the motor and the meanwhile low acquisition costs. As a result of the discrete switching states of the power transistors, the average of the three output voltages of a two-level inverter is a common mode voltage, which differs from zero. The common mode voltage is impressed into the motor winding by the inverter, and an image of the common mode voltage is produced across the bearings via the winding-to-rotor capacitance. The voltage applied to the motor bearings can exceed the dielectric strength of the lubricating film of the bearings and lead to discharge currents resulting in damage to the motor bearings. The winding-to-rotor capacitance is composed of a slot and an end-winding portion. In this article, an analytical determination of the end-winding portion of the winding-to-rotor capacitance is presented, which, in addition to the rotor geometry, considers the influence of materials with different permittivities. The method is validated by means of FEM simulations for different geometries and materials.