The study of double-star synchronous machine in normal mode and the control strategy in degraded mode

In order to increase the availability of the embarked actuators one solution is to equip them with double-star machines. To increase their compactness the permanent magnet synchronous machines (PMSM) are usually preferred. In this paper the degraded operating modes under fault conditions of a double star PMSM supplied by two independent electrical sources trough two VSI is studied. The considered faults are the open-circuit fault of one inverter switch and the voltage drop of one DC-source. For the voltage drop, one solution consists in canceling the supply of the star winding connected to the faulty element. For the open circuit fault of one inverter switch, we propose a new control strategy that reduces considerably the system losses. It consists in supplying not only the star winding connected to the healthy VSI but also the two phases of the other star winding by the two remaining healthy legs of the faulty VSI. The current waveforms and their amplitudes can be easily determined such as to minimize the losses and to cancel the torque undulations