Effects of the Floating Capacitor Voltage on the Torque-Speed Characteristic of an Open-End Winding Synchronous Reluctance Motor Drive

This manuscript investigates the torque-speed characteristics of a synchronous reluctance motor drive with an open-end winding (OEW) configuration. The machine is powered by standard two-level voltage source inverters (VSI), one supplied by a DC power source while the other connected to a floating capacitor (FC). The analysis considers the flux maps of a synchronous reluctance motor identified through experiments to account for the effect of the self-and cross-saturation phenomenon. The study reveals that the dual-inverter (DI) configuration with a FC can significantly extend the constant torque speed range and achieve unity power factor. In addition, the analysis demonstrates that the torque in the constant power speed range can be noticeably increased compared to the standard single-inverter (SI) configuration. With the full model of the OEW drive plant, the FC voltage can be purposefully selected to modify the drive torque speed characteristic to benefit the specific application. The advantages of the investigated synchronous drive architecture have been experimentally validated in different operating conditions with a purposely built set-up.