A novel modulation technique for fault tolerant, permanent magnet drives

High speed electrical machines are central in replacing existing systems in aircraft with electrical counterparts. An integrated, fault tolerant, permanent magnet machine and drive is considered. Aerospace systems require high power density and high reliability from systems. Availability may be increased by adding fault tolerance to the system design and power density may be increased by integration of subparts. Much design flexibility can be found when system subparts are designed jointly. To aid system integration losses are to be kept low. This can be done by selection of a topology which yields low losses, amongst other factors. A three phase inverter and full bridge inverters with bipolar PWM, unipolar PWM and phase shifted full bridge topologies are investigated, for which switching and conduction losses are calculated. Low frequency modulation is shown to be possible with the use of a phase shifted full bridge topology. This strategy also enables the use of IGBT devices in high speed machines where switching speeds limits the power level and rotational speed of such fast rotating machines.