A High Power Density Electric Machine Element

A direct current homopolar machine with liquid metal contacts can achieve high power density and efficiency. The analysis of a simple model of such a machine shows that a power density of several horsepower per pound at 90 percent efficiency is possible. The results of a design study of an experimental 280-pound 250- horsepower homopolar automotive transmission showed a 90 percent efficiency over a useful operating range. Problems arising during testing limited the efficiency to 75 percent.