Jang-Young Choi

Improved Analytical Model for Electromagnetic Analysis of Axial Flux Machines With Double-Sided Permanent Magnet Rotor and Coreless Stator Windings

This paper deals with the experimental verification and electromagnetic analysis of an axial flux machine with a double-sided permanent magnet (PM) rotor and coreless stator windings, based on analytical field computation. Employing a magnetic vector potential and a 2-D analytical model, magnetic fields produced by PMs are obtained. The 3-D problem is solved by introducing a special function for the radial position. Then, the analytical solutions for back emf, electromagnetic torque, and efficiency of the PM-type axial flux machines are derived by using the magnetic field solutions and considering simple equivalent circuits. The analytical results are validated extensively by 3-D FE results. Test results such as back-emf, torque, and efficiency measurements are also presented to show the effectiveness of the analyses.

Magnet Pole Shape Design of Permanent Magnet Machine for Minimization of Torque Ripple Based on Electromagnetic Field Theory

This paper deals with the magnet pole shape design of permanent magnet machines for the minimization of torque ripple based on electromagnetic field theory. On the basis of a magnetic vector potential and a two-dimensional (2-D) polar system, analytical solutions for flux density due to permanent magnet (PM) and current are obtained. In particular, the analytical solutions for mathematical expressions of magnets with different circumferential thicknesses can be solved by introducing improved magnetization modeling techniques, resulting in accurate calculations of electromagnetic torque. The analytical results are validated extensively by nonlinear finite element method (FEM). Test results such as back-emf measurements are also given to confirm the analyses. Finally, on the basis of derived analytical solutions, a reduction of torque ripple can be achieved.

Analysis and experimental verification of moving-magnet linear actuator with cylindrical Halbach array

This paper deals with analysis and experiments of moving-magnet linear actuators with cylindrical Halbach arrays. On the basis of analytical two-dimensional field solutions, this paper predicts magnetic fields, thrust, flux linkage, and back electromagnetic fluctuation. The results are validated extensively by comparison with finite element analysis. Test results such as thrust measurements are also given to confirm the analysis.

Improved Analytical Modeling of Axial Flux Machine With a Double-Sided Permanent Magnet Rotor and Slotless Stator Based on an Analytical Method

This paper presents the results of an experimental verification and electromagnetic field analysis for an axial flux permanent magnet (PM) synchronous generator (AFPMSG) with a double-sided PM rotor and slotless stator windings based on analytical field computation to offer improved analytical modeling method. An analytical approach to analyze the magnetic field distribution and estimate the equivalent circuit parameters is presented that dramatically reduces analysis time while maintaining high reliability. Since the flux leakage phenomenon is dominant in the inner and outer radii of this type of AFPMSG, it is specifically considered. In addition, an actual device was fabricated on the basis of one of the analysis models, and used to experimentally verify all of the analysis results.

Design and Electromagnetic Field Characteristic Analysis of 1.5 kW Small Scale Wind Power Generator for Substitution of Nd-Fe-B to Ferrite Permanent Magnet

With the main objective of substituting a generator without a conventional Nd-Fe-B permanent magnet (PM), this paper describes the application of ferrite PM to a 1.5 (kW) wind power generator and proposes a newly designed generator with similar performance and machine size as the equivalent conventional Nd-Fe-B PM generator. The conventional generator with Nd-Fe-B PM was slotless in order to eliminate the cogging torque resulting from the PM and the tooth-slot structure. The magnetic structure of the proposed ferrite generator was newly designed using an analytical approach to obtain satisfactory performance. All analysis results were validated through experiments with a manufactured model, confirming the possibility of substitution of Nd-Fe-B magnet with ferrite magnet in such generators.

Characteristic Analysis on Axial Flux Permanent Magnet Synchronous Generator Considering Wind Turbine Characteristics According to Wind Speed for Small-Scale Power Application

To use a permanent magnet (PM) synchronous generator to wind power generation systems, the wind turbine characteristics according to wind speed should be considered in the design stage and performance evaluation. Using the wind turbine characteristics provided by a manufacturer, we predict the performance of a wind power generator that uses an axial flux PM by analyzing the electromagnetic field characteristics. To avoid the long analysis time required by the three-dimensional finite element method because of the structural features of axial flux PM machines, an alternative analytical approach is presented, and its results are validated experimentally. In addition, we present an AC-DC-DC converter that is connected to the experimental setup for back-to-back tests in order to obtain constant output regardless of wind speed variations.

Analytical Torque Calculations and Experimental Testing of Permanent Magnet Axial Eddy Current Brake

This paper discusses the braking torque and normal force analysis of axial flux permanent magnet (AFPM)-type eddy current brakes (ECB) on the basis of an analytical field computation using a space harmonic method. On the basis of the magnetic vector potential and a 2D polar coordinate system, permanent magnets considering the eddy current effect are obtained. Additionally, by utilizing the derived analytical field solutions, the braking torque and normal force are predicted. Finite element analysis is employed to confirm the validity of the analysis and compare it with the experimental results obtained from the prototype AFPM-type ECB.

Vibration Analysis and Measurements Through Prediction of Electromagnetic Vibration Sources of Permanent Magnet Synchronous Motor Based on Analytical Magnetic Field Calculations

This study is devoted to the analysis of the vibration characteristics of a permanent magnet synchronous motor (PMSM) through investigation into its electromagnetic vibration sources. For this purposed, we derive analytical solutions for the magnetic fields generated by permanent magnets (PMs) in terms of a magnetic vector potential and a two-dimensional (2-D) polar coordinate system. A 2-D permeance function is also introduced in order to consider slotting effects. The electromagnetic vibration sources such as torque ripple, cogging torque, and radial force density are analyzed using these solutions. The analytical results are validated extensively with finite element (FE) analyses. The fast Fourier transformation (FFT) analysis is employed for investigating the specific harmonic orders of the electromagnetic vibration sources that affect the vibration of the PMSM. Finally, mechanical modal analysis results and test results such as vibration measurements are obtained to confirm the validity of the analysis methods presented in this paper.

Analytical Prediction and Measurements for Inductance Profile of Linear Switched Reluctance Motor

This paper describes analytical prediction and measurements for the inductance profile of a linear switched reluctance motor (LSRM). First, analytical solutions for flux density due to mover winding currents are derived, for the case when the mover is located at aligned and unaligned positions. Then, using the inductance at aligned and unaligned positions obtained from two-dimensional (2-D) analytical solutions and Fourier series expansion proposed in this paper, we predict the inductance profile of the LSRM analytically. Finally, inductance measurements are given to confirm the analysis

Thrust analysis and measurements of tubular linear actuator with cylindrical halbach array

This paper deals with design and analysis of the moving-magnet linear actuator with cylindrical Halbach array. On the basis of two-dimensional (2-D) finite-element analysis, this paper predicts thrust characteristics according to design parameters such as magnet height, air-gap length, coil thickness, and pole number. Then, we manufactured equipment made on an experimental basis of moving-magnet linear actuator with cylindrical Halbach array by employing parameters obtained from design results. Finally, this paper presents test results such as thrust measurements, which are given to confirm the finite-element analysis, according to load current and mover position.