A new subdomain and magnetic circuit hybrid model (SMCHM) is proposed for on-load field prediction in surface-mounted permanent-magnet (SPM) machines. Equivalent current sheets are introduced to represent the nonlinearity effect, whose values are obtained by magnetic circuit and correlated to boundary conditions in subdomain model. The number of reluctances in the magnetic circuit (MC) of proposed model can be selected flexibly according to nonlinearity effect. Instead of sectorial tooth in the conventional subdomain model, parallel tooth is considered in the proposed model to improve the accuracy. The SMCHM can accurately calculate the flux density distributions and electromagnetic performance considering the heavy nonlinearity effect under load conditions with fast computation speed. The finite element (FE) analysis is performed to validate the proposed model, which shows excellent agreement between them. A prototype machine is manufactured to further prove these predictions.

The magnetic potential drop in nonlinear iron can be replaced by equivalent current sheets on linear iron edges. Based on this principle, this paper proposes a nonlinear subdomain and magnet circuit hybrid model (SMCHM) for open-circuit field prediction in surface-mounted permanent-magnet (SPM) machines. The values of current sheets are calculated from magnetic circuit (MC) and used as boundary conditions in subdomain model. The finite element (FE) validation is performed, which shows SMCHM can accurately predict the magnetic field distribution and electromagnetic performance as nonlinear FE method does. The accuracy of SMCHM is significantly higher than the conventional subdomain model neglecting nonlinearity effect, and the computation speed of SMCHM is dramatically faster than FE model.

This paper develops an improved hybrid field model (IHFM) to predict the on-load performance of interior permanent-magnet (IPM) motors considering both iron saturation and slotting effect. It combines the air-gap analytical model based on modified conformal mapping with the reluctance mesh method for stator and rotor. The reluctance mesh method can accurately predict the rotor saturation and tooth-tip saturation even their field distribution is complicated due to armature reaction. Besides, IHFM will significantly accelerate computation speed using analytical model for air-gap region while keeping high accuracy. The finite-element analysis and experimental results of flat-type and V-type IPM motors are demonstrated to verify the effectiveness of the proposed model.

In this paper, a novel doubly-fed flux-switching permanent magnet (DF-FSPM) machine is proposed, whose armature windings are wound on both stator poles and rotor teeth. Different from the conventional FSPM machine in which the armature windings are only located in the stator, the rotor slot area is fully utilized in the DF-FSPM machine to improve the electrical loadings and thus the torque density. Moreover, it has potential of fault-tolerant operation, since it comprises two sets of armature windings which can work individually. The topology and operating principle of the machine is introduced with reference to a 12-stator-pole/10-rotor-tooth DF-FSPM machine. The electromagnetic performances of the optimized DF-FSPM machine and its FSPM counterpart machine are compared, including the induced voltage, inductances, torque capability, flux weakening capability, efficiency and power factor. It shows that the DF-FSPM machine can exhibit about 46.5% higher torque density than the FSPM machine, while its torque production per magnet volume is also improved by about 39.6%. In addition, the efficiency and power factor of DF-FSPM machine are higher than those of the FSPM machine. Finally, experimental validation is conducted on a prototype machine.

This paper proposes a simple and practical duty cycle modulated direct torque control (DDTC) for permanent magnet synchronous motors. The duty cycle of active vector is obtained using a duty cycle generator according to the torque error and motor speed, which can avoid the complex calculation process associated with conventional DDTC. The design details about the duty cycle generator are illustrated, and the stability of the proposed DDTC is analyzed, which ensures the reliable operation of the motor system. Experimental results are presented to validate the effectiveness of the proposed DDTC. Furthermore, the comparative evaluation of the proposed DDTC and conventional DDTC is conducted to verify the superiority of the proposed DDTC.

Nowadays, various analytical models (AMs) have been developed to analyze SPM machines with magnet shaping technique consideration, but their mechanism are all based on division and superposition theory, and numerous repetitive model calculations are required, which greatly attenuates the inherent speed superiority of AMs. In this article, a new fast AM is proposed, which can analytically solve the magnetic field generated from an arbitrary number of currents to obtain the magnetic field solution for shaping PM without any repetitive model calculation. Besides, five existing typical AMs considering shaping PMs are implemented and compared with the new model, viz., radial and tangential PM segmented method, traditional equivalent current method, and conformal mapping models. The comparison study investigates the adjustable model parameters, the dimension of the stiffness matrix, the number of repetitive model calculations, and the actual time consumption. Then, by finite element model validation, the new proposed model can maintain high accuracy and breakneck computational speed simultaneously. Ultimately, the broad application scope and rich added value of new AM are also expounded.