Piezoelectric fan cooling: A novel high reliability electric machine thermal management solution

Electric machine thermal management is critical for the correct operation of high power density electrical machines. This is, however, challenging to achieve in safety-critical applications where the reliability of the cooling system needs to be significantly higher than conventional solutions. Piezoelectric fans are presented here as a novel fault-tolerant forced cooling convective system for electric machines. Particle image velocimetry techniques in conjunction with infrared thermal measurements were implemented to map and quantify the flow fields generated by such a cooling arrangement as well as to determine the effective cooling enhancement. This paper also outlines the main design variables for such a system and highlights the main considerations to be accounted for to optimize the cooling potential. For the specific machine presented in this paper, the optimal fin/fan geometry resulted in mean flows in excess of 2.41 m/s and turbulence values in excess of 2.38 m/s, which resulted in an average convective heat transfer coefficient enhancement of 364.8% on the fin base and a further enhancement of 53.6% on each of the fin side walls. This, in turn, led to a 61.8% reduction in the electric machine heat sink cooling mass.