The necessary reliability of safety-critical aerospace drive systems is often partly achieved by using faulttolerant (FT) electrical machines. There are numerous published literatures on the design of FT machines as well as on control algorithms used to maintain drive operation with an incurred fault. This study is set to look at the rotor losses in three-and five-phase surface mount permanent magnet machines when operating in faulty mode in order to highlight the influence of the post-fault control strategy and winding configuration. Although the work presented in this study is mainly focused on FT control methodologies targeted at mitigating phase open circuit faults, the implications of short-circuit faults is also considered and discussed.
This paper looks in detail at a fault tolerant machine for direct drive application. The machine considered is a high pole number, concentrated wound machine developed for a safety critical aerospace application. The machine is designed to have a high p.u. inductance to limit short circuit current and negligible mutual inductance to have decoupled phase windings. Single and double layer winding configurations are compared. The machine has a heavy magnetic loading as its most onerous requirement is to hold a static load. High resulting air gap harmonics however induce substantial eddy current losses in the magnets and the solid rotor core. Due to the high thermal resistance path to these losses, the magnets may reach limiting temperatures during dynamic operation. This paper is set to analyze and compare two winding configurations and employ analytical modeling methods to evaluate the induced eddy current loss in the rotor.
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