Sampling problems using Mixed Random Modulation Techniques (MRMT) for the reduction of magnetic noise in traction motors

In order to reduce magnetic-acoustic noise emitted by asynchronous traction motors fed by inverter, a new kind of space vector modulation techniques have been developed. By using these, called mixed random modulation techniques (MRMT), a better ldquosound qualityrdquo of emitted noise is reached. They act modifying both SVM pulse position and SVM switching frequency. This action prevents the right sampling of motor currents, used by control algorithms. Basically the problem is due to the assumption that SVM pulse is centered into the switching period. This is wrong using MRMT. Through simulation, three strategies have been implemented. The chosen strategy has been tested together with the complete propulsion system of AnsaldoBreda tram Sirio.