Ronald John Krefta

Salient pole generators for belt-driven automotive alternator applications

Of all the electric machine types, conventional automotive belt-driven Lundell generators, and electrically-excited or hybrid permanent magnet-electrically excited synchronous salient pole generators are the only types that can utilize inexpensive control electronics consisting of a passive three-phase diode bridge and a simple, one power switch voltage regulator. In this paper, the replacement of Lundell automotive generators with either electrically-excited or hybrid permanent magnet-electrically excited synchronous salient pole generators is investigated on the basis of their better efficiency and the ability to provide output power beyond the 6 kW level. The design considerations and the test results are presented for a 42 V, 3.5 kW electrically-excited salient pole generator and for a 42 V, 3.5 kW hybrid permanent magnet-electrically excited salient pole generator. Specific design criteria, design simulations/analyses, and test results are presented and compared with a belt-driven automotive generator performance.

Comparison of full pitch and concentrated coil switched reluctance machines

While the switched reluctance machine (SRM) is traditionally a concentrated coil machine, efforts with full pitch windings have spurred interest. With the full pitch winding, twice the area of copper is energized at any given time as compared to the concentrated winding SRM, leading to potentially higher machine efficiency. This paper investigates the performance of 15 kW full pitch winding SRM under the following three current excitation patterns: unipolar, bipolar 120-degree conduction, and bipolar 180-degree conduction. In addition, the full pitch winding SRM is compared with the standard concentrated coil SRM. Finite element analysis (FEA) shows the highly nonlinear behavior of the mutual inductance of full pitch winding SRM. It is shown that the mutual inductance and self inductance change significantly depending on the current excitation patterns. Simulation results based on Simulink for each full pitch topology and concentrated coil SRM are presented at low and high speeds.