Design for improved fault tolerance in large synchronous machines

Fault tolerance is a basic requirement for modern electric motors and generators and can be achieved with a number of integrated approaches, like condition monitoring, post-fault control strategies and suitable system design architectures. In particular, this paper focuses on large synchronous machines (both permanent-magnet and wound-field ones) and discusses the main design provisions that can be adopted to improve their ability to withstand various kinds of fault. The fault-tolerant design solutions recommended for small-power machines are critically reviewed and their scalability to higher machine sizes is discussed also referring to practical industrial realizations. The most promising potential for fault-tolerance design is recognized in large low-speed high-pole-count permanent-magnet synchronous machines (e.g. for ship propulsion and wind power generation) thanks to their suitability for highly-modular multi-unit fractional-slot concentrated-winding architectures.