Line-start permanent magnet synchronous motors (LSPMSMs) have become superior to induction motors in general industrial applications due to their high efficiency, improved power factor, and enhanced torque density. However, the LSPMSM suffers the poor starting torque owing to the existence of the braking and pulsating torque at start-up, which seriously plagues its development. Therefore, this paper presents a novel LSPMSM with 6/8 pole changing stator windings, which can fundamentally improve the starting capability. At the beginning of the starting, the 6-pole stator windings are energized, whereas the rotor permanent magnets are 8 poles, so the braking torque and pulsating torque can be highly decreased. When the motor reaches a certain speed, the stator winding changes to 8 poles to pull into synchronization and stable operation. The design of the 6/8 pole changing winding is presented based on the slot-number phase diagram method. Then, the starting process of the conventional and the proposed pole changing LSPMSMs are analyzed and compared. Through the calculation of impedance parameters and the analysis of magnetic fields at the start-up, the torque components are calculated utilizing the analytical calculation method. Finally, the experiments are carried out to verify the validity and superiority of the proposed design and method.

This paper presents a novel 6/8 pole changing line-start permanent magnet synchronous motor (LSPMSM) for improving the starting and synchronization capabilities. A 6/8 pole changing stator winding with simple structure, convenient switching and speed detection capability is designed and studied. The synchronization process, which follows the 6- and 8-pole winding switching process, is analyzed. The effects of the switching speed, switching phase difference, and the rotor resistance on synchronization process are respectively studied. Moreover, on the basis of the improvement of the starting capability utilizing the pole changing starting strategy, the rotor resistance is appropriately designed smaller to simultaneously balance the synchronization capability. And the larger maximum moment of inertia that the motor can pull into synchronization validates the analysis. And through processing, both the starting and synchronization capabilities have been improved for the proposed 6/8 pole changing LSPMSM compared with the conventional 8-pole LSPMSM.

The interior permanent magnet synchronous machine (IPMSM) has been widely used in industrial applications due to its several favorable advantages. To further improve the machine performance, an improved nonlinear predictive controller for the IPMSM is proposed. In this paper, the maximum torque per ampere control law is firstly transformed to a linear function, according to the first−order Taylor expansion, and integrated with the control strategy. On this basis, an improved predictive control method is formulated by designing an optimized cost function through the input−output feedback linearization. Then the integral action is introduced to eliminate the influence of the load mutation and improve the steady−state control precision of the system. The stability of the control method is ensured by compelling the outputs to track the desired references without steady−state error. Finally, the simulation was established to verify the effective of the improved control method. Simulation results showed that the machine can reach the given reference speed without steady−state error within a short process, which means the machine has excellent dynamic and static performances. Furthermore, the machine has higher torque−to−current ratio by making full use of the reluctance torque. The simulation results verify the effectiveness of the improved control strategy.

This paper proposes an analytical model for a surface-mounted permanent magnet synchronous machine (SPMSM) with hybrid magnets. Through the magnetization analysis of the SPMSM with hybrid magnets, the expression of the air gap flux density is derived using the Laplace equation and the quasi-Poisson equation in which the effects of the thickness of the magnets and the angle of the isolation are considered. The relative permeability of the machine and the air gap field distribution under the slot effect are calculated by conformal transformation. The back electromotive force (EMF) based on the armature winding function is obtained by analyzing the winding law of fractional slot distributed winding. To further improve the torque performance and reduce the magnet cost, the multi-objective optimization based on the analytical model and particle swarm optimization (PSO) algorithm is carried out. The stability of the optimized model is proved by demagnetization analysis. Finally, the prototype based on the optimization results is fabricated, and the tested electromagnetic performances are compared to the finite element and analytical results to verify the effectiveness of the proposed design.

To ensure the starting performance of the single-phase induction motor with three parallel-connected windings, the transient performances and starting methods are studied in this paper. At first, the transient mathematical model of the motor is established according to the electromagnetic relations, and the simulation analysis is performed. Then two starting methods are proposed and studied. The first is starting with two additional starting capacitors. The second is the improvement of the first and has only one additional starting capacitor. By the simulation analysis, it is proved that both of them have good starting performances, and the starting method with one starting capacitor can simplify the starting circuit.

This paper presents a novel 6/8 pole changing line-start permanent magnet synchronous motor (LSPMSM) which can decrease braking torque and pulsating torque fundamentally and improve starting capability effectively. The impedance parameters of 6-pole winding and 8-pole winding are calculated in use of two-dimensional (2D) finite element analysis (FEA). Then the bipolar dynamic simulation model is built based on MATLAB/Simulink. And finally, in use of the simulation model, the influences of switching speeds and phase differences between induced electromotive force of 8-pole winding and applied voltage (Δθ) on impulse currents and synchronization when switching are analyzed, and the results show that the impulse currents are related to Δθ and the synchronization is related to both Δθ and switching speeds.