Interior permanent-magnet (IPM) machines exhibit relatively large spatial harmonics in phase voltages and high nonlinearity in torque production due to both the presence of reluctance torque and the magnetic saturation in stator and rotor cores. To simulate the real electromagnetic behavior of IPM machines, this paper proposes a high-fidelity and computationally efficient machine model considering the magnetic saturation, the spatial harmonics, and the iron loss effect based on the inverse solution of the flux linkages extracted via finite-element analysis (FEA). Neither FEA nor a derivative computation is involved in the time-stepping simulation; thereby, the proposed model is computationally efficient and numerically robust. The high fidelity of the proposed machine model is validated by both the FEA and the experimental results.

A High-Fidelity and Computationally Efficient Model for Interior Permanent-Magnet Machines Considering the Magnetic Saturation, Spatial Harmonics, and Iron Loss Effect

This paper describes the modeling of a permanent magnet synchronous machine (PMSM) by using lumped models (LMs). Designing electrical machines necessarily involves several fields of physics, such as electromagnetics, thermics, mechanics, and acoustics. Magnetic, electrical, electronic, and thermal parts are represented by LMs, whereas vibro-acoustic and mechanical parts are represented by analytical models. The aim of this study is to build a design model of a PMSM for traction applications. Each model is parameterized to optimize the machine. The method of taking into account saturation and movement is described. These fast, LMs make it possible to couple the software used with optimization tools. Simulation results are presented and compared with the finite-element method and the experiments performed.

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Multiphysics Modeling of a Permanent Magnet Synchronous Machine by Using Lumped Models

This paper presents a comprehensive computational fluid dynamics (CFD) model of a radial flux permanent magnet synchronous machine with interior magnets. In the CFD model, the water jacket cooling and a simplified model of the topology of the distributed stator winding are considered. The heat sources of the CFD model are determined from a finite-element analysis of the machine. The numerically determined temperature distributions of the machine are compared with measurement results from sensors located both in the stator and rotor. The particular focus of this paper is the analysis of the temperatures and the heat flow in the air gap and from the stator winding heads and the rotor to the inner air. Different operating conditions and two particular rotor designs with different inner air flow configurations are investigated. The potential of improving the thermal utilization of a rotor design with fan blades attached to the mounting plates of the rotor is shown.

A Detailed Heat and Fluid Flow Analysis of an Internal Permanent Magnet Synchronous Machine by Means of Computational Fluid Dynamics

Analytical calculations are effective in preliminary design stages and analysis of electric machines. In this paper, for axial-flux interior permanent-magnet (PM) eddy-current couplers, an analytical model is developed, which is able to deal with the complex machine geometry and take into account material properties such as iron saturation and PM characteristics. The design considerations of the machine are also presented. Moreover, the studied structure shows several advantages in terms of mechanical and magnetic performances over the couplers with surface PMs. The three-dimensional (3-D) finite-element method is employed in the analyses and evaluations. Finally, an experimental prototype is built to validate the model.

Analytical Modeling and Analysis of Axial-Flux Interior Permanent-Magnet Couplers

This paper is about the mechanical design and analysis of a yokeless and segmented armature axial flux permanent-magnet (PM) synchronous machine, which consists of two external rotors and an inner stator. Although this new electrical machine has many advantages such as high torque density, shorter axial length, and high efficiency, its mechanical construction is yet challenging. This is mostly due to the high axial force between the stator and the two rotors, which can be further increased by the inevitable manufacturing and assembly tolerances. Based on the determined geometric dimensions of the electromagnetically relevant components, a reliable mechanical construction is developed in this paper. Subsequently, stress, deformation, thermal, and modal analyses are performed based on finite-element method (FEM). Finally, the first prototype is successfully manufactured and measured. It can be concluded that the proposed construction is reliable and the measured data match well with the results of the electromagnetic analysis.

Development of a Yokeless and Segmented Armature Axial Flux Machine

This paper presents a simple nonlinear magnetic analysis for axial-flux permanent-magnet machines as an assistant design tool of 3-D finite-element analysis (3D-FEA). The proposed analysis consists of an equivalent magnetic circuit and an analytical model of air-gap permeances, including saturable permeances in the core. The proposed analysis is capable of calculating the flux distribution and torque characteristics under heavy operating conditions. We verify the accuracy of the proposed analysis by comparing the results with those of 3D-FEA for various design free parameters. After verifying the accuracy of the analysis, we present our analysis-based optimum design, which realizes the maximum torque density while maintaining efficiency at the desired value. Compared to the traditional 3D-FEA, the design method proposed here has the same accuracy, while the computation time is as short as 1/21.

A Simple Nonlinear Magnetic Analysis for Axial-Flux Permanent-Magnet Machines

This paper presents an optimum design approach to a two-phase switched reluctance motor (SRM) drive. The proposed drive is designed for use as a compressor drive in a small refrigerator as an alternative to the existing brushless dc motor with rare-earth magnets. In the proposed approach, three genetic algorithm loops work to optimize the lamination design and to meet the requirements for the target application while simultaneously fine-tuning the control parameters. To achieve design optimization within a realistic timescale, the repeated calculation required to obtain fitness evaluation does not use finite-element analysis but instead consists of a dynamic simulator based on an analytical expression of magnetizing curves and a geometric flux-tube-based nonlinear magnetic analysis developed specifically for this class of motor. Design results show that the proposed approach can autonomously find a feasible design solution of an SRM drive for the target application from a huge search space. The experimental studies using a two-phase 8/6 prototype manufactured in accordance with the optimized design parameters show the validity of the proposed design approach.

Optimum Design Approach for a Two-Phase Switched Reluctance Compressor Drive

This paper presents a novel approach for circuit-field-coupled time-stepping electromagnetic analysis of a saturated interior permanent-magnet (IPM) synchronous motor. To predict the drive performance quickly, the proposed approach consists of a dynamic simulator based on a novel nonlinear model of the d-q flux linkages of the IPM motor. The model can take into account not only the magnetic saturation but also the harmonics of inductance distributions and EMF waveforms. The validity of the model is verified from suitable simulation results of the instantaneous current and torque waveforms of the IPM motor. The proposed analysis realizes a dramatic reduction in the computation time compared to circuit-field-coupled time-stepping finite-element analysis, keeping analytical accuracy. A 10-kW 15 000-r/min prototype driven by a pulsewidth-modulation inverter was used for laboratory testing to verify the analysis. The experimental results showed quite reasonable agreement with the predicted instantaneous current.

A Novel Approach for Circuit-Field-Coupled Time Stepping Electromagnetic Analysis of Saturated Interior PM Motors

We present the design of a saliency-based sensorless drive interior permanent magnet synchronous motor (IPMSM) for a traction drive in hybrid electric vehicles (HEVs), and we introduce the sensorless safety operation region (SSOR), which accounts for cross-coupling magnetic saturation and harmonics of inductance distributions. The SSOR defines a working point under the maximum torque per ampere (MTPA) trajectory in which the motor can perform sensorless operation with a guaranteed performance in the steady state. The reliability of the SSOR was verified by experiments using two prototypes. The influence of the IPM motor geometry on the SSOR was then examined. Consequently, the design guidelines were established to obtain a suitable motor geometry that can maximize the torque capability and the stability during the sensorless drive. Under the restricted specifications of dimensions and requirements, the 100 Nm-10 kW 12-pole, 18-slot IPMSM is optimally designed for the target traction drive in HEVs. The validity of the proposed design was verified using a MATLAB/SIMULINK-based dynamic simulator.

Sensorless-oriented design of concentrated-winding IPM motors for HEV drive application

This paper presents the design of the concentrated-winding IPM motor under saliency-based sensorless drive with a high-frequency signal injection. Finite element analysis is used to examine the influence of the IPM rotor geometry on the operating region during the sensorless drive. On the basis of this analysis, a design procedure has been established to obtain a suitable rotor geometry that can maximize the torque capability during the sensorless drive. The 45Nm 5.5kW 6 pole 9 slot IPM motor is optimally designed for general industrial application. The validity of the proposed design is experimentally verified by using the prototype.

Yoshiaki Kano

Papers

A Simple Nonlinear Magnetic Analysis for Axial-Flux Permanent-Magnet Machines

Optimum Design Approach for a Two-Phase Switched Reluctance Compressor Drive

A Novel Approach for Circuit-Field-Coupled Time Stepping Electromagnetic Analysis of Saturated Interior PM Motors

Sensorless-oriented design of concentrated-winding IPM motors for HEV drive application

Sensorless-Oriented Design of Concentrated-Winding IPM Motor for General Industrial Applications