Minimization of harmful cage torsional resonances in traction motors by a combined mechanic-electronic optimization

This work reports an actual case of multiple-constraint engineering problem, risen when a suitable inverter control has been planned for Italian High-Frequentation Train drives (Treni Alta Frequentazione - TAF). GTO inverters produced harmful harmonic torques in the motor, and harmful harmonic interference with the signal-repetition system. Since switching frequencies should be moved up to solve the first problem and down to solve the second, an optimization problem rose involving mechanical and electrical systems. In this paper the on-field problems related to motor-converter interconnection are described, with particular reference to motor cage failure eventualities minimization by proper inverter control design combined with proper cage design. The case-study is described with simulations of the drive, and the optimization work is explained and discussed.