Yu-Seop Park

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.

Experimental Verification and Electromagnetic Analysis for Performance of Interior PM Motor According to Slot/Pole Number Combination

This paper reports on the experimental study on and analysis of the influence that the number of stator slots has on the performance of an interior PM (IPM) motor. First, for a conventional 6-pole IPM rotor, stators with 18, 27, and 36 slots that satisfy the same required and restricted conditions are designed. Next, the performances and parameters of each IPM motor, such as cogging torque, torque ripple, d- and q- axis inductance, and total harmonic distortion (THD) of back-EMF, are investigated using 2-D finite element analysis (FEA). Finally, test results for factors such as the d- and q-axis inductance, back-EMF, and cogging torque measurements are obtained to confirm the analysis results. From the results obtained in this work, it is concluded that the influence of the number of stator slots on IPM motor performance is quite significant.

Characteristic Analysis of Permanent Magnet Synchronous Machines Under Different Construction Conditions of Rotor Magnetic Circuits by Using Electromagnetic Transfer Relations

This paper presents a comparative analysis of the characteristics of high-speed permanent magnet synchronous machines (PMSMs) with diametrically magnetized rotors under different construction conditions of the rotor magnetic circuit. An analytical method is adopted to predict the magnetic field distribution and to calculate the electrical parameters by using the transfer relations based on a two-dimensional model in a polar coordinate system. In addition, three types of PMSMs with diametrically magnetized permanent magnets are proposed in this work. The electrical parameters are estimated and the magnetic field distribution is analyzed for those models, and these results are compared with those obtained using the finite element method; the two sets of results are found to be in good agreement. On the basis of the analysis results, a real model manufactured and the validity of our results is demonstrated by performing suitable experiments.

A Novel Concept and Proof of Magnetostrictive Motor

Electric motors have commonly been used to generate rotational motion, but provide inadequate torque, demand excessive power and are bulky in general. These disadvantages motivated development of a new type of rotary motor. All magnetostrictive motors that have been reported in the literature have utilized two or more linear magnetostrictive actuators to generate rotational motion for either inchworm or resonant types. Thus, this study presents a novel proof-of-concept of a magnetostrictive motor using a single Terfenol-D rod. The operational concept is based on the Wiedemann effect, that is, the twisting of a Terfenol-D rod due to magnetostriction when longitudinal and circumferential magnetic fields are applied simultaneously. To prove the concept, several ways to twist the Terfenol-D rod are suggested and subjected to simulation. Among them, the way with the best simulated results is adopted. A prototype is made and subjected to the experiments. A sawtooth-like driving signal with an input current from 0.5 to 1 A is applied to the magnetostrictive motor for the experiments. From the first experiments, it is observed that the rotational speed of the ball becomes higher with a lighter ball. The maximum rotation speed reaches up to 60 rpm with the lightest ball. The torque at this speed is calculated as 6.6 N·m. From the second experiments, it is observed that the ratio between the toroidal and solenoid currents causes the change of rotational direction of the rotor.

Electromagnetic Vibration Analysis and Measurements of Double-Sided Axial-Flux Permanent Magnet Generator With Slotless Stator

This paper examines the effects of the electromagnetic source on the vibration of a double-sided axial permanent magnet generator with a slotless stator depending on the ac and dc-load conditions. The slotless machine has no cogging torque. Most of the vibration originates from the torque ripple and axial force distributions, which result from the current load conditions. The 3-D finite element analysis results are compared with voltage, current, and torque measurements. The order tracking analysis of the vibration test data clearly demonstrates the dependence of the critical harmonics on the load conditions.

Comparative Investigation on Integrated System of Permanent Magnet Synchronous Generator and Power Converter Based on Machine Topology for Small-Scale Wind Power Application

This paper presents the comparative analysis and test results of permanent magnet (PM) synchronous generators based on machine topology for small-scale wind power application. For reasonable comparison, various design considerations, such as flux direction, rotor position, slot existence and PM materials, are dealt with under specific machine size limitation. Among the analysis models, five machines are manufactured for experimental verification, and the generators are integrated with AC-DC-DC converter to convert originally generated AC power to DC power. With our constructed experimental set, the electromagnetic characteristics based on measured current, and their performance are comparatively investigated under constant output voltage control condition.

Characteristic Analysis on the Influence of Misaligned Rotor Position of Double-Sided Axial Flux Permanent Magnet Machine and Experimental Verification

While axial flux permanent magnet (AFPM) machines are manufactured, their wrong assembly can be possible, such as misaligned PM rotor position of double-sided machine. Once the machines are assembled, detecting the misaligned rotor is hard, so the designers are required to have deep insight in its related and unexpected characteristics to prevent them focusing on other possible errors. Therefore, this paper deals with the characteristic analysis on the influence of the misaligned rotor position of double-sided AFPM machine and its experimental verification. In general, the AFPM machines have been analyzed by 3-D finite-element method (3-D FEM) due to their structural features, but it requires very long analysis time to consider various factors. For this reason, analytical approach is presented in order to consider all the cases of the misaligned rotor positions, and it is confirmed to be practical to detect the positions and to reduce analysis time with high reliability. With the analytical approach, the misaligned rotor position characteristics, such as back-emf and its total harmonic distortion are analyzed. Furthermore, all the analysis results are validated by 3-D FEM results and experimental verification.

Influence of Rotor Overhang Variation on Generating Performance of Axial Flux Permanent Magnet Machine Based on 3-D Analytical Method

This paper presents an analytical method based on transfer relations for an axial flux permanent magnet machine. The method takes the overhang length into account. Although considering the overhang structure is a very attractive way to increase the output power of the machine, optimization of its length has a heavy analytical burden when only the 3-D finite element method is employed for characterization of the electromagnetic field. Therefore, we derive accurate analytical solutions to dramatically reduce the time needed for analysis, and we present an experimental verification using a fabricated sample.