Power Density and Efficiency Comparisons of System-Compatible Drive Topologies

The benefits of variable-frequency drives (VFDs) have not been fully realized in many applications because they compete in the power density of legacy equipment, such as electromechanical motor controllers. This is particularly the case in Navy shipboard systems where sensitive equipment is in close proximity to VFDs. This paper compares the power densities, efficiency, and costs of both voltage-source- and current-source-based VFDs. A meaningful comparison is made based on actual hardware implementations that meet stringent power quality and electromagnetic compatibility requirements. The hardware results of a current-source-rectifier (CSR)-fed voltage-source inverter (VSI), or a CSR-VSI-based VFD, are provided in order to support the findings of this paper. Special consideration is given to operation at light loads.