Electrothermal effects of advanced electromagnetic materials on electrical loss and thermal characteristics of synchronous rotational machines

Abstract

Electrothermal characteristics of high speed synchronous rotational machine were studied experimentally and theoretically. Electrical rotating machines with three types of electromagnetic materials were fabricated to identify core losses in the iron cores of high speed synchronous machine. Dummy and isolated rotational machines were devised to measure pure mechanical losses and to examine conductive thermal resistances in stators. Results showed that mechanical losses are linearly proportional to driving speeds of electrical rotating machines, and that viscosity-induced mechanical losses in air are relatively negligible in comparison with friction-induced mechanical losses. It was found that an electrical rotating machine with 15HTH1000 electromagnetic material has relatively lower core and coil losses than the machines with 35PN440, 35PN250, thereby making it applicable for advanced high speed electric vehicular applications. In addition, core materials had a negligible effect on torque constants of the electrical rotating machines at a lower non-dimensional rotational speed of 0.2. However, the rotating machine with 15HTH1000 showed an 8.0% higher input current than did that with 35PN440 at a higher rotational speed of 0.9. Finally, thermal resistances in between iron cores and stators could be accurately characterized by a nonlinear empirical formula with the minimum R-2 value of curve fittings equal to 0.997 which reflects the convection effects on heat transfer enhancement.