Conceptualization and Efficiency Review of Integrated Chargers Using Six-Phase Machines

Three integrated battery charger concepts based on six-phase electrical machines (EMs) are presented in this article. State-of-the-art topologies for galvanically isolated integrated chargers are reviewed as a basis for a novel integrated charger using the electrical drive (e-drive) as an isolated dc/dc converter, while the rotor is kept at standstill. Efficiency levels up to 88% and a cost breakdown are reported. Furthermore, the well-known reconfigurations of three-phase machines are reviewed and proposed as a basis for novel series-connected boost-buck converters, in which each stage is represented by one of the two three-phase machine windings and power electronic converters. The efficiency analysis of a 144-kW e-drive under this 6.6-kW dc biased battery charging condition is presented. The EM iron losses are calculated with finite-element method (FEM) using new Steinmetz parameters based on ring core measurements reflecting charging conditions. In addition, the dc and ac copper losses are analytically calculated. Moreover, inverter losses are analyzed based on their own switching loss measurements. The calculated efficiency of the integrated charger is compared with measurement results. The difference in efficiency between both remains within ±1% and efficiency levels up to 93% are reported. Finally, silicon carbide technology shows enhanced efficiencies.