Power density and efficiency of system compatible, sine-wave input/output drives

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 electro-mechanical motor controllers. This is especially the case in Navy shipboard systems where sensitive equipment is in close proximity to VFDs. In this context, this paper compares the power densities, efficiencies and costs of a Voltage Source Converter (VSC), Current Source Converter (CSC) and mixed VSC/CSC based VFDs. A meaningful comparison is made based upon an actual hardware implementation that meets stringent power quality and electromagnetic compatibility (EMC) requirements. Hardware results of a CSC/VSC based VFD are provided in order to support the findings of the study. Special consideration is given to operation at light loads.