Evaluation of High-Tech Electrical Steel in a High-Speed Permanent Magnet Synchronous Machine for an Aircraft Application

A major design challenge of high-speed high-power machines is the dissipation of heat resulting from the occurring losses. Higher rotational speeds require a high base frequency of 1 kHz. Thus, such a design will have high hysteresis losses and eddy current losses in its iron paths. Thinner electrical sheets and iron alloys with lower specific loss, e.g., cobalt-iron, are used as one countermeasure. However, given the challenge of an aircraft application with the demands for low weight and a small build volume, further aspects such as the difference in density and the heat transfer characteristics have to be considered as well. This paper compares an already existing machine design built with silicon-iron electrical sheets to further iterated designs based on a very thin cobalt-iron material at the same operational conditions. Furthermore, a new machine with higher pole pair number is designed to take advantage of the low loss coefficients and, consequently, make use of a higher operational frequency. The pros and cons of these machines are evaluated using finite element and numerical simulations for electromagnetic and thermal aspects. The results show the advantage of high-tech thin cobalt-iron alloy electrical steels in the field of electrical machines with a high power-to-weight ratio of 10.31 kW/kg for the active part of the machine compared to 7.35 kW/kg using a silicon-iron material.