Analysis and design of homopolar motors and generators

The homopolar DC motor converts electrical energy into mechanical rotational energy using the Lorentz force. The same machine can be used to convert mechanical energy to DC electrical energy. In order to better understand homopolar motors and their applications, an analog model was created using PSPICE. Forces opposing the motor rotation include back-voltage, eddy currents, moment of inertia, and sliding friction and are analyzed in detail. Resulting forces are discussed and calculated analytically. The capabilities of the homopolar machine operating as both as motor and generator are considered. Using current research from the University of Missouri on rail guns and coil guns which utilize similar electromagnetic forces for linearly-accelerated applications, the maximum efficiency of the homopolar motor is examined. Experimental data was collected and used to compare simulation results and verify the accuracy of motor performance. Sensitivity analysis and the estimated maximum machine efficiency obtained from simulation are presented.