Yoshiaki Kano

Simple nonlinear magnetic analysis for permanent-magnet motors

This paper presents a simple nonlinear magnetic analysis for a surface-mounted permanent-magnet synchronous motor as an assistant design tool of finite-element analysis (FEA). The equivalent magnetic circuit of the motor used in the proposed analysis is composed of the saturable permeance tips in the stator teeth for considering the local magnetic saturation. As a result, the proposed analysis is capable of calculating the flux distribution and the torque characteristics in the presence of magnetic saturation. The effectiveness of the proposed analysis is verified by comparing with three-dimensional (3-D) FEA in terms of the analytical accuracy. The computation time is greatly reduced as short as 1.5 s while the 3-D FEA requires as much as 32 min for the same evaluation.

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

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.

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

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.

Simple nonlinear magnetic analysis for permanent magnet motors

This paper presents a simple nonlinear magnetic analysis for surface-mounted permanent magnet synchronous motor (SPMSM) as an assistant design tool of FEA. The equivalent magnetic circuit of the motor used in the proposed analysis is composed of the saturable permenance tips in the stator teeth for considering the local magnetic saturation. As a result, the proposed analysis is capable of calculating the flux distribution and the torque characteristics in the presence of magnetic saturation. The effectiveness of the proposed analysis is verified by comparing with 3D-FEA in terms of the analytical accuracy. The computation time is greatly reduced as short as 8 seconds while the 3D-FEA requires as much as 32 minutes for the same evaluation.

Design of Saliency-Based Sensorless Drive IPM Motors for General Industrial Applications

This paper presents the design of saliency-based sensorless drive interior permanent magnet (IPM) motor for the general industrial application. To design accurately, considering magnetic saturation and cross-coupling effects are in FEA-based performance predictions. The reliability of the FE simulation is verified by experiment using a prototype. Then, the influence of the IPM rotor geometry on the feasibility region is examined. Consequently, the design guideline is established to obtain a suitable rotor geometry which can maximize the torque capability under the sensorless drive. Under the restricted specifications of dimensions and requirements, the 45Nm-5.5 kW 6-pole-9slot IPM motor is optimally designed. The validity of the proposed design is experimentally verified using the prototype.

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

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 has realized a dramatic reduction in the computation time compared to circuit-field-coupled time- stepping FEA, keeping analytical accuracy. A 10 kW-15,000 rpm prototype driven by PWM inverter was used for laboratory testing to verify the analysis. The experimental results showed quite reasonable agreement with the predicted instantaneous current.

A novel multi-pole permanent magnet synchronous machine with SMC bypass core for magnet flux and SMC field-pole core with toroidal coil for independent field strengthening/weakening

This paper presents a novel multi-pole permanent magnet synchronous machine for the traction applications in which both high torque capability at low speed and wide speed operating range are required. The origin of the proposed machine construction is from a hybrid stepper machine, but the uniqueness lies in the utilization of soft magnetic composites (SMC) as magnet flux bypass core and filed-pole core with toroidal coil. Because of the magnetically three-dimensional isotropic nature of SMC, the SMC-bypass core for magnet flux makes it possible to avoid unnecessary magnet mmf loss due to a passage through inter-lamination airgap. For the same reason, the SMC-field pole can deliver three-dimensional flux and the mmf of the fitted field toroidal coil can theoretically contribute to providing independent field strengthening/weakening capability. First, the rough design of the proposed machine based on an equivalent magnetic circuit analysis is described. Second, the performance prediction and the design refinement using 3D-FEM are demonstrated

A Design Approach for Direct-Drive Permanent-Magnet Motors

This paper presents a design approach of a direct-drive permanent-magnet (PM) motor for a medium-sized injection-molding application. In the proposed approach, genetic-algorithm (GA) loop works to optimize the lamination design in order to meet the requirements for the target application. To achieve the design optimization within a realistic time scale, the repeated calculation required to obtain fitness evaluation does not use finite-element analysis (FEA) but consists of a geometric flux-tube-based nonlinear magnetic analysis developed specifically for this class of motors. The validity of the proposed design approach is verified through several comparative studies on the design results with FEA using a 942- 88.8-kW three-phase multipole interior PM motor, which is designed by the proposed optimizing GA approach.

Torque-Maximizing Design of Double-Stator, Axial-Flux, PM Machines Using Simple Non-Linear Magnetic Analysis

This paper presents a torque-maximizing design of a double-stator, axial-flux PM machine using a simple non-linear magnetic analysis. The proposed analysis consists of a geometric- flux-tube-based equivalent-magnetic-circuit model. The model can take into account not only the magnetic saturation but also the three-dimensional(3D) flux distribution. The proposed analysis has realized a dramatic reduction in the computation time compared to 3D-FEA, keeping reasonable analytical accuracy. At first, the validity of the proposed analysis is examined for the various design parameters. After verifying the accuracy of the torque computation of the proposed analysis through the comparisons with 3D-FEA, an 8-pole axial-flux PM machine with double-stator-single-rotor is optimally designed. The performance of the optimized motor are finally verified by 3D-FEA.

Optimum Design Approach for Two-Phase Switched Reluctance Compressor Drive

This paper presents an optimum design approach for 2-phase switched reluctance motor (SRM) drives. The proposed drive is designed for compressor drives in a small-sized refrigerator as an alternative to existing brushless DC motor with rare-earth magnets. In the proposed approach, three GA loops work to optimize the lamination design as well as simultaneously fine-tuning the control parameters. To achieve the design optimization within an acceptable computation time, the repeated-calculation required to obtain fitness evaluation in the proposed approach does not use finite element analysis, but consists of a dynamic simulator based on an analytical expression of the magnetizing curves and a geometric flux tube-based nonlinear magnetic analysis developed specifically for this class of motors. The design results show the proposed approach can autonomously find a feasible design solution of SRM drive for the target application from huge search space. The experimental studies using a 2-phase 8/6 prototype manufactured in accordance with the optimized design parameters show the validity of the proposed design approach.