Operation Method of Non-Salient Permanent Magnet Synchronous Machine for Extended Speed Range

This paper proposes an operation method for the extended speed range of a surface-mounted permanent magnet (SPM) synchronous machine. The proposed method is based on a novel winding changeover scheme. The SPM machine has low synchronous inductance and hence poor field weakening capability. To enhance its field weakening capability, the permanent magnet's flux linkage can be reduced by performing a winding changeover. The proposed operation method increases the base speed of the machine by 3.83 times. In contrast to available two-inverter schemes with four thyristor switches, the proposed scheme utilizes a single-inverter topology drive and six bidirectional switches for the winding changeover. The machine works in two modes: cumulative and differential. In the cumulative mode, winding has a high induced back electromotive force (EMF), whereas in the differential mode, it falls by 3.54 times. The base speed increases approximately by the same ratio. After the mode switch, field weakening control is applied to the machine to further increase the speed range to 3.83 per unit. The proposed operation method was simulated in a commercial two-dimensional finite element method software in both modes under no-load and load operating conditions. The transient analysis was performed during the winding changeover, and speed range operation analysis was also carried out. The experimental results are provided to verify the extension of the speed range operation of the proposed novel winding changeover scheme for an SPM machine.