This paper investigates the surface-mounted permanent-magnet (SPM) and the interior permanent-magnet (IPM) motors for high-speed applications. An SPM motor and an IPM motor are designed with the same power/speed rate and the same key dimensions. Finite-element analysis is used to compare the mechanical, electromagnetic, and antidemagnetization performances of the two motors, and lumped parameter thermal networks are involved to compare their thermal performances. It can be concluded from the comparisons that the IPM motor has comparable electromagnetic performances with the SPM motor in high-speed operations, and its costs and torque per PM weight are superior to those of the SPM motor. However, its rotor structure is not as robust and is prone to irreversible demagnetization.

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In this paper, the thermal field of a large scale permanent magnet embedded salient pole wind generator (PMESPWG) is investigated by using the computational fluid dynamic (CFD) modeling. To reduce the calculation, only one quarter model of the PMESPWG is established according to its symmetry. Based on the electromagnetic analysis and the empirical equations, the copper loss, stator iron loss and rotor loss are calculated and then used as the heat source in the thermal field analysis. The temperature distributions in the generator are predicted by finite element method (FEM). The calculated results are discussed and verified by the measured ones. The analysis results show that the modelling method can provide a valuable evaluation for electromagnetic and thermal designs in the design stage. The generator temperature variation with fan speed is also discussed, which supplies a reliable reference for the cooling system optimization.

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Wind power generation has increased rapidly in China over the last decade. In this paper the authors present an extensive survey on the status and development of wind power generation in China. The wind resource distributions in China are presented and assessed, and the 10 GW-scale wind power generation bases are introduced in details. The domestic research status of main components of WP system is then elaborated, followed by an evaluation of the wind power equipment manufacturers. Finally, the outlook for the development of the wind power utilization in China is presented.

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High speed permanent magnet machines (HSPMMs) have a promising future in applications such as aeronautics and astronautics, energy and ultra-precision manufacturing. This paper enumerates various stator and rotor structures and materials of the HSPMM in literature. Then different losses in the HSPMM are summarized in aspects of stator iron loss, copper loss, rotor eddy current loss and air friction loss. Various motor temperature rise calculation methods and three kinds of high speed rotor bearings are compared, followed by an overview of the problems linked to the rotor strength and dynamics analysis. Finally, development trends of the HSPMM related technologies are summarized and prospected.

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Based on the linear field theory and the limiting nonlinear theory, respectively, the eddy current losses in thick iron plates and thin laminations are formulated. Two equivalent permeability calculation models are developed to take into account the saturation effects occurring in the corresponding ferromagnetic materials. By enabling the approximate treatment of the magnetic field saturation, the nonlinear eddy current problem is reduced to the linear one. The proposed approach to the linearization of the field analysis is investigated by comparing the results of the linear analysis using the equivalent permeability with those of the nonlinear finite element analysis and experimental data.@en

This paper presents a novel switched-flux memory motor (SFMM) by artfully incorporating the flux-mnemonic concept into the conventional switched-flux permanent magnet machine. The magnetic susceptibility of AlNiCo PM provides the flexible online controllability of air-gap flux by imposing a transient current pulse. To uniformize magnetization levels of PMs, a time-divisional magnetization strategy (TDMS) is proposed. Due to the uniqueness of hysteresis nonlinearity and instability regarding AlNiCo PM operating point, the time-stepping finite element method (TSFEM) dynamically coupled with a nonlinearity-involved parallelogram hysteresis model (NIPHM) of AlNiCo PM is performed to investigate the electromagnetic performance of the proposed SFMM. The results derived from the combinative algorithm verifies the flux-adjustable capability of the proposed motor equipped with TDMS and the validity of the proposed NIPHM.

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This paper investigates the losses of a high-speed permanent magnet motor. The iron losses are calculated by a model that can consider the skin effect and rotational loss. The rotor eddy current losses are estimated by a fast hybrid method that can consider the end effect. Pulse-width modulation (PWM) harmonics brought by the voltage source inverter (VSI) are considered in the loss calculations. Then the temperature distribution of the motor is evaluated by using the calculated loss results and computational fluid dynamic (CFD) modeling. Finally, based on the CFD results, the motor structure is optimized to achieve better rotor cooling. The outer slots are closed to force the cooling air flow through the rotor surface. Calculated temperature distributions and optimization results are verified by measurements.

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This paper investigates the electromagnetic and thermal performances of the open-circuit air cooled high-speed permanent magnet motor (HSPMM) with Gramme ring windings. Take a 36 kr/min, 75 kW HSPMM as an example, the electromagnetic losses, in particular the rotor eddy current loss and the stator iron loss of the motor are calculated. The influences of switching frequency and air gap length on these losses are studied. Then, a computational fluid dynamics (CFD) model is composed to calculate its coolant flow parameters and the temperature distribution. Based on the CFD results, a lumped-parameter thermal network (LPTN) is created and verified. Then, a 24 kr/min, 140 kW prototype with the same structure and cooling configuration is designed using the LPTN. Experiments show that the calculated results are with reasonable accuracy. Finally, a sensitivity analysis is applied to the 140 kW prototype based on the LPTN to disclose the influences of different parameters on the rotor permanent magnet temperature rise.

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This paper presents a detailed magnetic equivalent circuit (MEC) to improve the analysis accuracy and reduce computation time in modeling of axial flux permanent magnet machines. In the proposed MEC model, the magnetic saturation, armature reaction, leakage flux, and rotor rotation are considered to calculate the machine's static characteristics. The investigated machine structure and feature are first introduced. Then, the air-gap flux density distribution, back electromotive force waveform, and the average torque are calculated with the proposed method. Finally, the accuracy of the proposed method is verified by the 3-D finite-element method, and good agreements are achieved.

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This paper presents the design, analysis and verification of a 150 kW, 24 krpm high speed permanent magnet motor (HSPMM). The HSPMM is a two-pole motor with Gramme ring windings, which can shorten the end winding length and improve the rotor stiffness. The design procedure based on analytical methods, including the rotor mechanical design, magnetic design and cooling design is described. Then a prototype designed by the proposed design techniques is further verified by numerical methods including finite element analysis (FEA) and computational fluid dynamics (CFD) and experiments.

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The most accurate method to design the stator coreless axial flux permanent magnet machine is the 3D finite-element analysis, which is exceedingly time-consuming. To solve this problem, this paper presents an analytical design method. Firstly, the analytical model of the 3D no-load magnetic field distribution of the machine is proposed. Analytical expressions of the back electromotive force of the machine are derived based on the model by using the winding function method. Inductance and resistance are calculated based on parameters such as the estimated ending connection length. Machine losses are analyzed in detail and analytical equations of them are presented. Then equations for the steady state performance are derived bases on the equivalent circuit of the machine. Finally the proposed design method is applied to three prototype machines with different rate powers and winding configurations. The prototype machines were tested and the calculated results are compared with the experimental ones, showing good agreements.@en

In order to reduce the error introduced by the conventional motor model in the induction motor soft starting simulation, an induction motor model with variable parameters is proposed by investigating the variation patterns of the equivalent circuit parameters during starting. Based on the operating principle of the induction motor, the proposed model estimates the motor equivalent circuit parameters in starting and steady state directly from the nameplate data. During starting, the rotor resistance and leakage reactance are varied according to the increasing rotor speed to ensure that the simulation model is close to the actual motor on critical operating points. The proposed model is applied to soft starting simulation of a 16MW induction motor in Matlab. Simulation results are verified by experiment and the variation of the starting time is within 3%. It can be seen that the proposed model is simple in construction and high in accuracy, and can simulate the starting procedure of the induction motor validly.@en

A three-dimensional analytical modeling of the magnetic field of the stator-ironless axial flux permanent magnet (AFPM) machine under open-circuit condition is presented in this paper. It involves the analytical solution of the governing field equations in the region between back-irons in the cylindrical coordinate, in which the magnets are assumed to be axially magnetized and have constant relative recoil permeability. The proposed modeling method is applied to a specific AFPM machine, and the analytical results are in good agreement with those of three-dimensional finite element analysis (FEA).

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