Electric Drive Based on an Open-End Winding Surface PM Synchronous Machine with a Floating Capacitor Bridge

A speed control scheme is presented for a three-phase surface permanent magnet synchronous machine with an open-end stator winding fed by a three-phase inverter and a floating bridge inverter. The latter is used to compensate for the reactive power of the main inverter and to maximize the active power received by the motor, without exceeding the available stator current and dc-link voltage. To reduce the switching losses, the dc-link voltage of the floating inverter bridge varies depending on the operating condition of the motor and the controllability requirements of the system. The experimental results show that a significant improvement in the speed range at constant power is achievable, proportionally to the dc-link voltage of the floating bridge inverter.