A Review of Thermal Designs for Improving Power Density in Electrical Machines

More electric aircraft is a promising solution to the problems of fuel consumption, emissions, and noise faced by the aviation industry. Electrical machines with high power density are essential to improve the overall performance of more electric aircraft. The huge difference between the maximum and the rated output of electrical machines shows that the performance does not reach the present limit of the electromagnetic design. Improving thermal designs is an important and effective way to increase power density at the present stage, as the temperature rise limit of materials is the main obstacle to restricting the performance of electrical machines. In this article, a variety of thermal designs are comprehensively reviewed and critically discussed according to different cooling positions. Next, an analysis of suitable thermal designs for different applications of electrical machines in more electric aircraft is presented. Subsequently, cooling capacity and additional mass of the thermal designs, which are the two key determinants of improving power density, are estimated and compared. Moreover, the reliability and cost of the thermal designs are discussed in depth. This work contributes to a thorough understanding of thermal designs in improving the power density of electrical machines and guides their future designs and applications in more electric aircraft.