Design and Analysis of Permanent Magnets in a Negative-Salient Permanent Magnet Synchronous Motor

Abstract

The Ld of a negative-salient permanent magnet synchronous motor (NSPMSM) is greater than Lq. When a NSPMSM is operating at or below the rated speed, the id is flux-intensifying current, which can improve the flux density of permanent magnets (PM). First, a NSPMSM is proposed and compared with a positive-salient permanent magnet synchronous motor (PSPMSM). The d-axis and q-axis equivalent magnet circuits of the NSPMSM are then established. According to the limitation of the equivalent magnet circuit, the PM dimensions formula and optimization of the finite element method (FEM), PM dimensions are determined, and the constant power speed ranges of the two motors are calculated. Second, the influence of the saliency ratio on the internal power factor angle and the average flux density of PM at different internal power factor angles are calculated. Third, the flux density of PM in two motors are calculated when the windings are short-circuited. Finally, the bypass function of the NSPMSM magnetic bridges during the flux-weakening state is analyzed. The results show that the flux-weakening magneto motive force (MMF) of the NSPMSM is smaller at high speed, the short-circuit current (SCC) is smaller when the windings are short-circuited, and the magnetic bridges protect the PM in the flux-weakening state, so the flux density of PM is larger.

Design and Analysis of Variable Leakage Flux Flux-Intensifying Motor for Improve Flux-Weakening Ability

“…This property enables the FI-IPM motor to obtain positive reluctance at a positive flux-intensifying current i d [18]. Compared with the maximum torque of the conventional IPM motor achieved at negative flux-weakening current i d , the risk of irreversible demagnetization of the FI-IPM motor is lower [19]. Besides, the flux-intensifying effect can reduce the flux-weakening current at a high speed [20].…”

Design and Performance Investigation of 3-Slot/2-Pole High Speed Permanent Magnet Machine

“…However, several challenges occur in the manufacturing of high-speed PM machines due to the replacement of field winding by PM. In advanced high-speed PM machines, a parasitic loss is considered rotor eddy loss, as it only contributes to a small amount of the machine's overall power [5], [6]. Precise calculation of eddy current loss is essential in PM machines for high performance and efficiency.…”

Multi-Objective Optimal Design of the MFW-Ipm Machine for Improve Flux-Weakening Ability

“…This type of machine possesses the unique characteristic of d-axis inductance L d larger than that of qaxis inductance L q . It means that the machines can obtain the maximum torque at a positive d-axis current [15], so the risk of PM irreversible demagnetization is reduced [16]. The characteristic can improve the flux-weakening ability of the machine.…”