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

Abstract

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. INDEX TERMS efficiency and power factor, extended speed range, field weakening, SPMSM, winding changeover scheme, winding reconfiguration

Investigation Study of Multi-Mode Multi-Speed Operation Method for Surface-Mounted Permanent Magnet Synchronous Machines

“…The flux linkage is expressed as Note that the term decreases by 3.73 times compared with that in (20). This results in a decreased back EMF and torque.…”

“…Numerous winding switching methods have been proposed. Among them, the most widely used methods are series/parallel switching [7], [8]; wye/delta switching [9], [10]; tapped winding switching [11], [12]; and cumulative/differential switching [14]- [20]. It is also possible to change the pole number via winding switching to improve the starting torque of line-start permanent magnet synchronous machines [21], [22].…”

“…In reference [20], a cumulative/differential machine operation that implemented winding switching for a single inverter was reported. This method achieved two-speed operation, and the back EMF in the differential mode was reduced 3.52 times compared with that in the cumulative mode.…”

“…However, as it could be operated in only two discrete modes, its practical application was limited. This paper proposes a modified winding switching scheme based on reference [20] to achieve a multi-mode multi-speed operation of an SPMSM. In this study, we combined the cumulative/differential and wye/delta switching methods.…”

“…Thus, we can operate the machine in four modes, and the back EMF can be reduced by up to 6.47 times. The four operation modes and increased speed range offer more flexibility in terms of practical application compared with [20], whereas the winding arrangement remains unchanged.…”