Decoupled Control of Series Connected Split-Phase Synchronous Motors with Open Circuit Fault with Eight-legged Inverter

The advantages of multi phase drives are lower torque ripple, fault tolerance, higher power density, lower harmonic currents and lower DC-link voltage requirement. Split phase machine is a multi phase machine with two-three phase windings phase shifted by 30° which helps in reduction of sixth harmonic torque pulsations. In this paper, two series connected split phase synchronous motors connected with proper phase sequence are supplied with single six phase VSI. The same is modeled and is implemented experimentally. Series connected synchronous motors are difficult to operate under open circuit fault. Post fault MMF (magneto-motive force) equations are developed to obtain rotating magnetic field with constant magnitude. This is achieved by applying a voltage to the neutral point using an additional inverter leg. The proposed method is experimentally implemented and verified.