| Abstract |
High frequency bearing currents are a parasitic phenomenon that affects inverter-fed induction machines, causing damage and wear to the mechanical bearings, which might lead to unexpected failures, increase of the machine downtime and reduction of its lifespan. This paper focuses on the discharge (EDM), circulating and rotor-to-ground bearing currents of an totally enclosed fan cooled (TEFC) 4-pole 110_kW-cage induction machine with grease-lubricated ball bearings type 6316 C3. How are the bearing currents affected by changes in the components of the electrical circuit that feeds this machine_ The investigated system consists of a two-level PWM voltage source inverter, four different passive filters such as a) common-mode ring core current filter, b) common-mode ring core current filter with small phase-to-ground capacitances, c) differential mode voltage sine filter and d) dual-mode voltage sine filter, with three different types of motor cables (shielded vs. unshielded) with different lengths_of 50_m, 150_m or 300_m. So, in total forty-five system arrangements including the system without filter were tested. The highest reduction of bearing currents was measured with the dual-mode voltage sine filter in all cable configurations. If the rotor is grounded e. g. by a slip ring brush, shielded cables reduce also the rotor-to-ground bearing currents. |
