The Role of End-Winding in Building Up Parasitic Capacitances in Induction Motors

Modern variable-speed electrical drive systems have been widely used since the commercialization of power electronics-based frequency converters. Nevertheless, there are specific parasitic phenomena associated with inverter-induced bearing currents, which are always accompanying drive systems fed by pulse-width-modulated frequency converter outputs. In electrical machines, when considering capacitive bearing currents, the major role in forming the parasitic current path is played by the stray capacitance between the stator winding and the rotor surface. This capacitance can be divided in different proportions between the lamination stack zone and the end-winding part of the electrical machine depending on the machine power range. The outline of the current study is to investigate the share of the end-winding in building up the total winding-to-rotor capacitance as a function of the machine size.