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In this study, a novel design for a tilted spoke‐type hybrid permanent magnet synchronous motor (TH‐PMSM) that uses two types of permanent magnet (PM) materials is proposed to reduce the consumption of rare‐earth PM materials. The key feature of this motor is securing space by tilting the permanent magnet, so that more PMs can be used in the limited rotor space. In addition, based on the centre axis of the rotor, the rare‐earth magnets are positioned deeper inside than ferrite PMs to maximise the torque density and reduce the leakage magnetic flux that occurs around the centre of the rotor. Moreover, unlike ordinary spoke‐type rotors, it is designed with an integral core like the rotor of the interior permanent magnet synchronous motor (IPMSM), so it is structurally safe even at high speeds. To ensure that the proposed motor is efficiently designed, the output torque, PM cost, cogging torque, and torque ripple were compared with those of the conventional rare‐earth PM motors with the same overall dimensions. The validity of the proposed motor was verified by the results of a finite element method simulation and experiments on the fabricated motor.

In magnetomechanical applications, it is necessary to calculate the magnetic force or torque of specific objects. If the magnetic fluid is involved, the force and torque also include the effect of pressure caused by the fluid. The standard method is to solve the Navier–Stokes equation. However, obtaining magnetic body force density is still under controversy. To resolve this problem, this paper shows that the calculation of the torque of these applications should not only use the magnetic force calculation method, but also consider the mechanical pressure using an indirect approach, such as the virtual work principle. To illustrate this, we use an experimental motor made of a nonmagnetic rotor immersed in a magnetic fluid. Then, we show that the virtual work principle in appropriate approach can calculate the output torque of the nonmagnetic rotor due to pressure of the magnetic fluid. Numerical analysis and experimental results show the validity of this approach. In addition, we also explain how the magnetic fluid transmits its magnetic force to the stator and rotor, respectively.

A method has been developed for demonstrating a flow nanogenerator by using a mixture of magnetic nanofluid (MNF) and bubbles in a fluid circulating system, and notable phenomena related to the power generation properties of the nanogenerator have been explored. MNF is widely used in various areas because of its interesting magnetic properties under an external magnetic field. The objective of the proposed technique is to obtain the induced electromotive force (EMF) based on Faraday’s law due to the flow of MNF in a closed-circulating system. To maximize the induced EMF, magnetic nanoparticles (MNPs) should pass through the induction coil with a perpendicular magnetization direction in accordance with Faraday’s law. To control the magnetization direction of the MNPs, a permanent magnet was employed to produce an external magnetic field that considers the Brownian and Neel motions. To obtain a continuously induced voltage, a circulation system was implemented ensuring the flow of the MNF in the closed cycle. Further, power generation properties were investigated considering electric, magnetic, and fluidic effects. To analyze this complicated physics, a multiphysics analysis was used to calculate the flow pattern of the MNF according to its magnetic properties, and the acquired results were compared with those obtained from the experiment. From these experiments, we investigated the generation properties of the nanogenerator considering the flowrate of the MNF as well as the presence or absence of bubbles within the MNF. Our experimental tests demonstrated that the continuous power generation mode was successfully achieved with a mixture of MNF and bubbles.

A generalized Korteweg–Helmholtz (GKH) force density method was implemented incorporating the virtual air-gap scheme and the finite-element method for evaluating magnetic body force density and mechanical deformation. Until now, several generalized force calculation methods adopting the virtual air-gap scheme have been developed and successfully applied to contact and mechanical deformation problems. The KH force density method is well known and can be derived with theoretical completeness, and it can be changed into the tensor formulation for calculating force density and total force on the electromagnetic body. This KH is numerically stable compared with the conventional Maxwell (MX) stress tensor method, because it adopts the tensor difference at an interface. However, the KH also has difficulty calculating the contact force density and body force density. Therefore, here, we developed the GKH force density method employing the virtual air-gap scheme. In addition, the mechanical deformation was tested quantitatively and compared with those from the conventional force calculation methods, including the MX, the KH, the equivalent magnetic charge method, and the Kelvin force density method. To verify the mechanical deformation due to the GKH, we implemented the GKH and compared the mechanical deformations between the several numerical results.

In this paper, the motion of conductive particles is modeled and analyzed using a coupled equation. A neutral conductive particle obtains charge when it comes into contact with an electrode. The forces acting on a particle consist of electric, drag, and gravitational forces. When the electric force is dominant over the other forces, a particle lifts up toward the upper electrode. The electric force on a particle is calculated using surface charge distribution, which is analyzed using the finite-element method. The dominant forces on the particles are used as a driving force in Newton’s motional equation to analyze a particle motion. The analysis results show that the total charge, which enables the particle to lift off, is calculated using the coupled equation with respect to the applied voltage. The experiment using a spherical conductive particle is conducted, and the experiment result is compared with the numerical one to validate the numerical method.

It is difficult to calculate the magnetic force of an object of magnetic material in contact with other objects using the existing methods, such as Maxwell stress tensor method, magnetic charge method, or magnetizing current method. These methods are applicable for force computation only when the object is surrounded by air. The virtual air-gap concept has been proposed for calculating the contact force. However, its application is limited to magneto-static system. In this paper, we present the virtual air-gap concept for contact surface force in the eddy-current system. Its validity and usefulness are shown by comparison between numerical and experimental examples.

This study was conducted to evaluate the use of biological monitoring to determine the factorsthat influence the effects of exposure to pyrethroid pesticides among highland cabbage farmers. Urine wascollected from farmers who was cultivating Chinese cabbage in the relatively highground in Gangwon-do themorning following pesticide application and was analyzed for cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethy-lcyclopropane carboxylic acid (DCCA) and 3-(2,2-dibromovinyl)-2,2-dimethyl cyclopropane carboxylic acid(DBCA). Factors affecting exposure to pesticides, such as wind speed, spraying location, and the use ofprotective gear, were also investigated. Statistical analysis was performed by the Kruskal-Wallis test. Ouranalysis indicated that highland cabbage farmers were exposed to a higher level of pesticides than the generalpublic or other types of farmers. When the wind speed was low, workers who sprayed pesticides wereexposed to a higher level of pesticides compared to the exposure level in an assistant. However, there was nodifference in exposure between the two when wind speed was high.Key words biological monitoring, highland cabbage farmer, pyrethroid pesticide

A new design method for topology and shape optimization to preserve high-voltage systems is proposed. The level set technique for the topology optimization is employed with the finite-element method. For the velocity field in the level set equation, the continuum sensitivity formula is used for accurate information of the electric field effect on the topology and shape variation. This technique is applied to three practical examples and the optimum designs of insulating dielectric for the systems are obtained. The optimum designs could suppress troubles, such as thermal deterioration or electrical breakdown, in the systems.

This research shows that it is possible and effective to predict the cogging torque waveform of the interior permanent magnet (IPM) machine using only an analytical model. Based on the proposed virtual permanent magnet (PM) concept, IPM can be considered as surface PM having zero height and unit relative permeability, and then it is used for calculating the cogging torque with conventional technique. Among the evaluation methods for cogging torque, lateral force method, which is based on lateral force acting on stator teeth, is selected. For the validation of proposed concept, finite element analysis is used. From the analysis results, it is shown that our new proposed concept presents good performance in terms of optimal position of peak cogging torque, cogging torque waveform, and the peak value. Therefore, the proposed concept can be useful in design of IPM requiring several computation processes.

This paper investigates the effect of slot-pole combination on harmonic loss such as iron loss and eddy-current loss in wind generators with high-temperature superconductor field winding. In order to study the effect of stator configuration, three wind generators having the same rotor structure but different stators were purposely designed to produce 11 MW. In the analysis, 2-D time-stepped finite element analysis was used to estimate flux density waveforms, and then harmonic iron loss in the stator yoke and rotor eddy-current loss were obtained. From the simulation results, we showed that the harmonic effect on stator iron loss is not significant because magnetic loading by field winding dominates. Meanwhile, we found that the eddy-current loss in the rotor by harmonics of magneto motive force strongly depends on the slot-pole combination.

This paper presents a new analytical model for estimating the cogging torque in a multi flux-barrier interior permanent magnet machine (IPM). The model is based on a lumped circuit that considers the saturated bridge in the rotor's iron core. Finally, the cogging torque waveform of a multi flux-barriers IPM can be effectively predicted with the assistance of both the proposed virtual permanent magnet concept and the superposition principle. Utilizing the proposed concept, an IPM containing multi flux-barriers may be recognized as a multiple surface permanent magnet machine (SPM) having zero height and unit relative permeability. After decomposing the flux density of air-gap (Bg) in the IPM into multiple air-gap flux densities for a virtual SPM, the model is used for estimating the individual cogging torques which will be added or subtracted to the total cogging torque. For validation of our proposed concept, finite element analysis (FEA) was used. From the analysis results, it is shown that the proposed concept is practically effective in terms of finding optimal position, peak cogging torque, and waveform.

Purpose – The purpose of this paper is to present a new numerical technique, called adaptive level set method, for use with the finite element method. Design/methodology/approach – A conventional level set method using the smeared Heaviside function has been employed for shape and topology optimizations. The smeared Heaviside function yields an indistinct interface boundary, and so can increase computational time and cause numerical errors. The adaptive level set method does not use the smeared Heaviside function. To coincide with the material interface, it processes the zero level as the boundary data of element meshing. Findings – Usefulness and accuracy of shape optimization using the adaptive level set method are shown by comparison to the conventional level set method. A shape optimization procedure using the adaptive level set method is introduced. Numerical examples are employed to explain how the adaptive level set method is applied. Originality/value – The adaptive level set method is proposed to relieve the interface problem of the conventional level set method. Shape variation in the optimization is calculated from the continuum sensitivity analysis.

This study was performed to evaluate the exposure level of organophosphorus and pyrethroidpesticide to floriculture workers and florists. The urinary dialkylphosphates, metabolites of organophosphorusinsecticides, including dimethylphosphate (DMP), diethylphosphate (DEP), dimethylthiophosphate (DMTP),diethylthiophosphate(DETP) and pyrethroids of metabolites, cis/trans DCCA, DBCA, and 3-PBA wereanalysed to evaluate the exposure of organophosphorus and pyrethroid pesticide to floriculture workers andflorists. The concentration of DMP is highest in floriculture workers. but the concentration of DETP ishighest in retail florist. The concentration of 3-PBA is highest in floriculture workers. The amount oforganophosphorus and pyrethroid pesticide expusure is highest in flower workers, wholesale florist and retailflorists are followed. The management for reducing pesticide exposure to floriculture workers and wholesaleflorist is required.Key words dialkylphosphate, GC/MSD, orgnophosphate insecticides, pyrethroids insecticides, urine

It is well known that the conventional force methods have failed in calculating the contact forces when magnetic materials are touching each other. This paper presents a general scheme for computation of contact forces without any thin air-gap insertion between the materials. Maxwell stress tensor method, one of the most popular methods, is adopted by using the virtual air-gap scheme. By using the scheme, general contact situations such as iron versus iron, iron versus magnet, magnet versus magnet, irregular shaped objects, and high field saturation can be resolved in a consistent way. The proposed scheme is easily applicable by just implementing in the post-processing step. For validation, a simple electromagnet system was devised and fabricated for comparison of numerical calculations and experimental measurements.

In this study, Ant Colony Algorithm(ACO) was used for optimal model. ACO which are metaheuristic algorithm for combinatorial optimization problem are inspired by the fact that ants are able to find the shortest route between their nest and food source. For applying the model to water distribution systems, pipes, tanks(reservoirs), pump construction and pump operation cost were considered as object function and pressure at each node and reservoir level were considered as constraints. Modified model from Ostfeld and Tubaltzev(2008) was verified by applying 2-Looped, Hanoi and Ostfeld’s networks. And sensitivity analysis about ant number, number of ants in a best group and pheromone decrease rate was accomplished. After the verification, it was applied to real water network from S water treatment plant. As a result of the analysis, in the Two-looped network, the best design cost was found to $419,000 and in the Hanoi network, the best design cost was calculated to $6,164,384, and in the Ostfeld’s network, the best design cost was found to $3,525,096. These are almost equal or better result compared with previous researches. Last, the cost of optimal design for real network, was found for 66 billion dollar that is 8.8 % lower than before. In addition, optimal diameter for aged pipes was found in this study and the 5 of 8 aged pipes were changed the diameter. Through this result, pipe construction cost reduction was found to 11 percent lower than before. And to conclusion, The least cost design model on water distribution system was developed and verified successfully in this study and it will be very useful not only optimal pipe change plan but optimization plan for whole water distribution system.

In this paper, magnetic buoyancy force on nonmagnetic solid object submerged in magnetic liquid was simulated and measured. For the evaluation of the force, a multi-physics approach of hydrostatic equilibrium considering magnetic body force as well as gravity is presented. The magnetic body force should be regarded as an additional forcing term in the momentum equation of hydrodynamics. It is also shown that the virtual air-gap based Kelvin’s force formula is a useful method for the calculation of force distribution in the magnetic liquid. The experimental result which was performed by a load-cell measurement system agreed quantitatively well with the numerical one. Key Words : Multi-physics simulation, Buoyancy, Magnetic liquid, Hydrodynamics, Hydrostatics, Magnetic body force* Corresponding Author : Dept. of Electrical Engineering, Kyungpook University, Korea.E-mail : tochs@knu.ac.krReceived : October 17, 2012; Accepted : December 18, 2012 1. 서 론 자성유체는 자성을 가지는 액체로서 우주의 진공상태에서의 헬멧과 같은 기기의 기밀 기압유지와 액체연료제어를 위한 장치, 회전축 실링장치, 능동식 댐퍼등과 같은 산업분야에서 응용이 된다[1][2]. 고체가 아닌 유체상태의 자성체인 자성유체는 고체자성체가 보이는 현상과 여러모로 다른 현상을 보여 학자와 연구원들의 이론과 실험적 관심의 대상이기도 하다.본 논문에서는 자성유체를 전자기장 관점에서 어떻게 해석하여야 하는 가를 보여주고자 한다. 자성유체 내에서 기계적 역학과 전자기적 역학이 서로 얽힌 상태에서 전자기력에 의한 영향을 어떻게 구하는 것이 옳은가에 대한 탐구의 일환으로, 자성유체 내의 비자성체에 미치는 힘에 대한 연구결과이다. 이론적 검토는 수치해석과 실험에 의하여 검증하였다. 자성유체 내부에 그림 1과 같이 자석과 비자성체가 있다고 가정하면, 비자성체는 자석과 멀어져가는 방향으로 힘을 받게 된다. 이러한 현상은 자석이 자성유체를 끌어당겨 자석의 주변에 몰리게 함으로서 발생하는 자연스러운 현상의 결과로서 이로 인해 비자성체가 밀려나게 되는 것이다. 자석의 입장에서 보면 동일한 반발력이 반대방향으로 작용할 것이다. 중력이나 다른 힘은 없다고 가정하면 이 시스템에 부가되는 힘은 오로지 전자기적인 원인에 의해서일 것이다. 일반적으로 전자기력 계산에 많이 사용하는 맥스웰응력법Maxwell stress method을 사용하여 비자성 고체에 미치는 전자기력을 바로 계산하려고 하면 우선 폐쇄면closed surface을 그 주위에 설정하여야하는 데, 비자성체의 경우 이 면을 비자성체 표면 바로 위 또는 바로 아래로 설정하면 그 면 내부의 힘 계산은 영이 될 수밖에 없다. 전자기력이 비자성체는 영향을 미치지 않기 때문이다. 자성유체 전체를 감싸는 면을 설정하여 자성유체에 미치는 힘을 계산 한다 하더라도 이 힘은 비자성체에 미치는 실제의 힘과 대응되는 것으로 볼 수가 없다. 이러한 방식으로 자성유체에 미치는 힘을 계산하려하면 자석과 자성유체 사이에 미치는 힘도 계산하여야 하는 데, 이 또한 자석을 제외한 자성유체를 어떤 폐쇄면으로 감쌀 것인가 하는 개념적 혼돈을 야기한다. 더구나, 자성체나 유전체의 표면이나 공극에서 표현되는 맥스웰 응력 또는 맥스웰 표면력은 물리적인 의미가 없고 물체 전체에 미치는 힘 또는 체적력에서만 의미가 있다[3][4].그림1 자성유체에 잠긴 영구자석과 비자성체Fig. 1A permanent magnet and a nonmagnetic object when both are submerged in a magnetic liquid 이러한 모순들의 해결과 일관된 역학적 설명을 위해서는, 비자성체 또는 자성유체에 전체에 미치는 힘을 구하는 접근이 아닌 자성유체내부에 미치는 체적력을 중력과 함께 고려하여 비자성체의 표면에 미치는 압력을 구하는 접근법이어야 한다. 즉 전자기 체적력을 추가로 고려한 정유체역학hydrostatics이어야 한다. 본 논문에서는 자성유체의 자기장

In large-scale motors, iron rack of magnets can be used for the production efficiencies. In this paper, the magnetic forces of single bed and double bed types of the rack were compared using the virtual air-gap method. Also, the carved grooves on the rack are proposed for improving the magnetic binding forces.

This paper presents a nine-phase permanent-magnet synchronous motor (PMSM) drive system based on multiple three-phase voltage source inverters. The nine-phase PMSM was developed as a traction motor for an ultrahigh-speed elevator. The mathematical model of the motor was simplified through symmetry of the system. Using the simplified model, the drive system can be controlled by the well-known d-q control theory. The feasibility and validity of the drive system were experimentally demonstrated at the world's tallest elevator test tower. Moreover, an additional experiment was performed to ensure the fault-tolerance capability of the system.

Magnetic force calculation methods such as Maxwell stress, virtual work principle, equivalent magnetic charge, and equivalent magnetizing current are widely used until now. The force density is still controversial issue even though it is common sense that all of these methods have legitimate results. The surface force densities of each method are quite different with each other in the point of numerical result and final expression. In this paper, it is shown that a unified expression of body force density is derived using virtual air-gap scheme for an analytic model in which cylindrical magnetic material with a vertical current runs through its center.

A smooth interaction body force density and torque were evaluated in permanent-magnet (PM) systems by using the virtual air-gap scheme coupled with the finite-element method. The virtual air-gap method has been successfully applied to soft magnetic materials for evaluating the force density, global contact force, and optimal shape design. These force-calculating methods employing the virtual air-gap scheme have been called generalized methods. Unlike the soft magnetic materials, there have been few research works related to force density and global force in PMs. We evaluated the interaction body force density, which represents the smooth and pure interacting force field between PMs and other magnetic components, by withdrawing the self-body force density from the total body force density. From this result, the smooth interaction body force density can explicitly show the trend of resulting mechanical torque. The torque by the self-body force density, of course, was zero and the torque, here, was evaluated by using the total body force density. From the previous results, the torque by total body force density shows some numerical instability, and we used edge-force components in each element for removing the numerical instability. Finally, the global quantities, such as global force from the smooth interaction body force density and torque from the total body force density, were successfully evaluated and verified by the conventional force calculating methods, such as the Maxwell stress tensor method and the virtual work principle method.

This paper presents an optimization method of the back EMF for the double layered (double air gap) large-scale BLDC motor by using a Latin-hypercube sampling strategy. In order to drive the large-scale BLDC motors in parallel and multiphases, the back EMF of inner stator is equal to the back EMF of the outer. A new configuration of the double layered BLDC motor is also proposed for the compactness and high efficiency of the system. By the optimization, it is concluded that the skew angle and the thickness difference between the outer and inner magnets have important roles in synchronization and same magnitude of the back EMF, respectively.

In this paper, we present an efficient modeling scheme based on a level set approach for electromagnetic systems including moving parts. The combination of finite elements and the level-set technique allows us to trace the interface variation on a fixed mesh of finite element. It does not require remeshing for the evolving geometry. The material data of moving objects is easily set using the Heaviside function obtained from the level set equation. For the driving force of dynamics equation, the total force on dielectric object is obtained by integrating the body force density of electric charge method. The numerical results of the test model show usefulness of the proposed scheme.

In this paper, a numerical scheme for obtaining ferrofluid shape formation is presented using the revisited Kelvin's force formula. The formula adopts the newly appreciated field intensity from the original Kelvin's concept and the virtual air gap scheme. For the hydrostatic equilibrium subject to magneto-static field, both electromagnetic and gravitational body forces should be considered. The free surface profile of ferrofluid can be obtained through numerical iterations based on the fact that the pressures on the free surface should be the same. Test models are presented as validations of the proposed scheme.

In this paper, an implementation of virtual work principle in virtual air gap is proposed for the calculation of contact and body forces. To calculate the proper values of the magnetic field at virtual air-gap, we exploit the generalized magnetic source methods. It is shown that appropriately sized virtual elements can be allocated in the virtual air-gap by one-dimensionally extending the virtual gap while keeping the previously calculated field intensity. Both an element's and total forces can be obtained by virtual distortion of the concerned virtual elements. The proposed method provides a good accuracy even when the two contacting objects have the different permeability. As a validation, numerical examples are presented for the force distribution and total force.

Three different Kelvin force expressions were expanded by incorporating the virtual air-gap scheme to calculate the total force and the distributions of force density. Conventionally, the Kelvin force density can be expressed by using two different fields such as an external applied field and total field acting on a dipole. Until now, the Kelvin force density with total field (KV) has been used for calculating the total force and force density. Since there is no single well-accepted manipulating technique, it has been difficult to directly compute the Kelvin force by adopting the external field approach; however, using the virtual air-gap scheme, the direct calculation of both Kelvin force density with external applied field (KVE), and with total field (KVT) as the local distributions of body force density was able to be evaluated. We tested three numerical analysis models to verify our proposed method. First, the nonlinear magnetic material was considered and compared the total force with different gap distances to contact position. Second, the distributions of force density were compared to each other. An irregularity aroused in the distributions of force density by the KVE and KVT. Finally, to remove the irregularity, one possible approach, forming sliced-tube regions aligned with the field direction, was suggested and examined

It is very important to calculate the forces at the distributed parts of electric machines for the prediction of performance. For this, calculation of distributed electromagnetic forces is certainly required. In this paper, the body force distributions of electric machines such as surface permanent magnet, interior permanent magnet and synchronous reluctance motors are presented and discussed for the first time using the recently developed body force calculation methods. It is shown that the total force of each part agrees well with its integrated body forces. Besides the interior permanent magnet motor, other types of machines are dealt with in the main paper

It is known that the magnetic attractive force generally occurs between the magnetic materials in the magnetic field. However, the recent study reports that the ferromagnetic bodies in the magnetic field can experience the repulsive force by changing the surface shape of them. In this paper, the repulsive electromagnet in the magnetic system is optimized to generate the maximum repulsive force. Continuum design sensitivity analysis and adaptive level set method are employed for the shape optimization. Continuum design sensitivity analysis is used to derive the sensitivity formula as a closed form and to calculate the sensitivity value on the boundary of the magnetic materials for using finite element method (FEM). Adaptive level set method is used to express complicated evolving geometry because it has an advantage to reduce numerical errors of sensitivity value compared with the results of the conventional method.

In this paper, it is newly presented and discussed that when two magnetized materials are sufficiently close, total force of magnetic materials can be variable by depending on the adjacent surface shapes. This means that when two magnetized bodies are adjacent or in contact, the total force is not uniquely defined and depends on the bordering surface shapes even though the total volume is maintained as a same level. It shows that the range of variable force falls into even repulsion to attraction.

In this paper it is shown that Kelvin's formula can be implemented in a simple way using the external field, which is calculated from the virtual air-gap scheme recently proposed by the authors. External fields of all finite elements come from only one FEM solution. This implementation provides consistent numerical results of force calculation whether a magnetic body is in contact with another or not. The validity of this proposed method for magnetic force calculation is shown by numerical comparisons with other well-known methods

In this paper, the virtual air-gap formulae for electromagnetic forces are derived from the generalized forms of equivalent source methods, such as magnetic charge and magnetizing current. The virtual air-gap approach is based on the idea that insertion of infinitesimally thin air gap causes no real variation of electromagnetic field system. For total force calculation of a magnetic body in contact with other ones of ferromagnetic or permanent magnets, the virtual air-gap formulae can employ the conventional force methods, such as Maxwell stress, magnetic charge, and magnetizing current. The virtual air-gap approach is validated by numerical test results

In this paper, a new, general form of the equivalent magnetizing current method is proposed for calculating the total force of magnetized bodies in contact, including ferromagnetic and permanent magnet. This method is formulated in way similar to the generalized equivalent magnetic charge method. It provides consistent numerical results of force calculation, whether or not one magnetized body is in contact with the other one. The validity of this evaluation method for magnetic forces is shown by close observation of the formulae and numerical test results

To analyze the mechanical dynamic characteristics of electromechanical system, we present a new and fast method using the reduced modeling technique for the levitated conductor. As of now, to solve this electromechanical system, the finite element method (FEM) or the boundary element method (BEM) employing the finite difference time-stepping scheme is used. These approaches, however, need too much solving time because the system matrix equation should be solved at each time step. Additionally, when the operation condition is changed or it needs more incremental steps, the system should be solved from the beginning again. To reduce the solving time, we use the circuit parameters of self- and mutual inductances which are evaluated using the FEM and the conductor segmentation. The formulated ordinary differential equations are solved using the fourth-order Runge-Kutta method. To show validity and usefulness of this proposed method, the TEAM Workshop Problem 28 model is tested, and the results of the experiment and time-stepping FEM are compared to this new method.

For the mechanical structure design of electric machines, each force component on the parts of an electric machine need to be separated. In this paper, a separation scheme of each torque component is presented. It is based on the magnetic force density analysis of the general formulation of equivalent magnetic charge method and Lorentz force density. The force density analysis can be applied to all parts of the system region including the inside of material and the interface of different materials. An interior permanent magnet motor and a surface permanent magnet motor are adopted for numerical test in this paper. Their numerical results show validity and usefulness of the presented method.

The conventional force calculation methods can be applied only for the total force of the objects surrounded by air or vacuum. In this paper, a new general form of equivalent magnetic charge method is proposed for calculating force density and total forces of materials in contact including ferromagnetic and permanent magnet. It provides surface force density on the interface of different materials. The validity of this method is shown by direct observation of the formulas and numerical tests.

Alkyl cellosolves include ethylene glycol monomethylether, ethylene glycol monoethylether, ethylene glycol monobuthylether. And their urine metabolites are methoxyacetic acid, ethoxyacetic acid and butoxyacetic acid. The current analytical method for urinary alkoxyacetic acid is liquid-liquid phase extraction. But the liquid-liquid phase extraction method needs a more complex pre-treatment process and has a low recovery rate. We determined the appropriate extraction solvent and its flow rate. We also evaluated the non-absorptive rate and recovery rate according to particle size. Finally we developed a convenient solid phase extraction method for the analysis of urine cellosolve metabolites. As a result, the recovery rates for methoxyacetic acid, ethoxyacetic acid and butoxyacetic acid were 100.4 +/- 1.6%, 100.2 +/- 1.8% and 100.7 +/- 10.0% respectively, when acetone was used as the extraction solution. The most appropriate flow rate was 0.1 ml/min. At a particle size of 140-200 mesh, non-absorption percentages for methoxyacetic acid, ethoxyacetic acid, butoxyacetic acid were 3.2 +/- 0.3%, 1.0 +/- 0.1% and 1.1 +/- 0.1%, and the recovery rates according to particle size were similar. Further evaluation of the recovery rate and non-absorptive rate according to the mini column shape, stationary phase and recovery rate with various extracting solutions is required.

This paper proposes a design method for optimizing the rotor winding shape of HTS motor. The design objective is to maximize the flux-linkage of stator winding with a given amount of superconductor volume. The increase of flux-linkage results in output-power increase, compact size and quench-reliable characteristic. The optimization algorithm is a design sensitivity analysis where the HTS critical current condition is taken into account. First, the shape of rotor winding is optimized to give a boundary shape of smooth curves. Second, with the shape the rectangular sizes of windings are approximately obtained for easy manufacture. Finally, the rectangular sizes are also optimized for fine-size tuning. The proposed design method is applied to the 100-hp HTS motor.

This paper emphasizes on the magnetic charge method to determine the magnetic force density due to mechanical deformation for nonlinear magnetic materials. For incompressible and nonlinear magnetic materials, theoretical expression for magnetic force density due to mechanical deformation generating from Korteweg-Helmholtz force density (KH), Kelvin force density (KV), and magnetic charge force density (MC) methods have been proven to be equivalent. The Maxwell stress tensor method (MX) and MC have been employed to calculate magnetic force density due to mechanical deformation. Numerical implementation of the equivalent magnetic charge method is quite simple, so the local force density for nonlinear material can be readily obtained. To exhibit validity and usefulness of the proposed method, an axisymmetric actuator and an electromagnet with highly saturated cantilever plate have been examined.