Fail-safe capability of a high voltage IGBT inverter source

The aim of this paper is to explain the intrinsic fail-safe capability of a high-voltage IGBT(c) inverter source. The inverter is an imbricated cells structure which provides redundancy. The major failures can be either a wro ng gate voltage (malfunctioning of the driver board, auxiliary power supply failure, dv/dt disturbance) or an intrinsic IGBT failure (over-voltage/ava lanche stress, temperature overshoot). The IGBT failures are studied and sh ow that no opening of the bondings can appear and consequently no risk of e xplosion. Owing to the imbricated cells structure, an IGBT failure can be w ithstand a few switching periods, with nevertheless non-optimized output wa veforms. The design and the lab-test of a sensor able to perform monitoring and failure diagnosis are also presented. This real-time diagnosis allows either a safety stop or a remedial control strategy based on the reconfigur ation of the control signals. The real-time reconfiguration allows to decre ase internal stresses and to optimize the shape of the output voltage. In t his case, a fail-safe operating may be gained for high power applications.