Finite Element Analysis Of Magnetic Field Research Articles

Core Loss Calculation for Soft Magnetic Composite Electrical Machines

Soft magnetic composite (SMC) materials are especially suitable for developing electrical machines with complex structure and three-dimensional (3-D) magnetic flux path. In these SMC machines, the magnetic field is in general 3-D and rotational, so the mechanism and calculation of core loss may be quite different from that in traditional electrical machines with laminated steels in which the magnetic field is restrained. This paper investigates the calculation of core loss in a permanent magnet claw pole motor with SMC stator core. First, core loss models are developed based on the experimental data on SMC samples by using a 3-D magnetic property tester. Then, 3-D magnetic time-stepping field finite element analysis (FEA) is conducted to find the flux density locus in each element when the rotor rotates. The core loss is computed based on the magnetic field FEA results by using the developed core loss models. The calculations agree well with the experimental measurements on the SMC motor prototype.

Finite Element Analysis and Evaluation of Stator Insulation in High Voltage Synchronous Motor

In this paper, two-dimensional finite element analysis (FEA) is used to compute the electric field in stator slot of a synchronous motor. The electrical insulation between the conductors and the edges of slot is evaluated. The relationship between size of air gap and electric field in this air gap is discussed. Secondly the slot-opening electric field, which is not uniform, is calculated by using three-dimensional finite element method. The discussion of insulation structures of slot-opening for anti-corona is conducted. A distributed equivalent circuit model is constructed for the inter-turn insulation under the impulse over voltage excitation. The inductances of the coils are achieved by using magnetic field FEA considering skin effects. The capacitances of the coils are calculated by using electric field FEA and analytic equation respectively. Finally, the evaluation of stator insulation using finite element method is presented.

Finite-Element Analysis of Magnetic Field and the Flow of Magnetic Fluid in the Core of Magnetic-Fluid Seal for Rotational Shaft

There has been developed a mathematical model for analyzing the magnetic field in the core of magnetic-fluid seal (MFS) with account of nonlinear magnetic properties of the materials for magnetic core and shaft. To provide for the numerical realization of this model, there was used a finite-element method and Comsol software package.

2-D Magnetic Field Analysis of Air Cylinder with MR Sensor

As a type of solid state switch, MR (magnetoresistive) sensor detects the air cylinder piston’s position in pneumatic control system. The construction and working principle of the air cylinder with MR sensor are introduced. Using 2-D magnetic field finite element analysis (FEA) method, the magnetic field distribution of air cylinder with piston motion is analyzed. Simulation results are given. The magnetic flux density characteristics are compared between piston wear or not.

영구자석조합형 축방향 자기베어링 시뮬레이션 및 실험

In this paper, an actuator model of the thrust magnetic bearing for the flywheel energy storage is derived using magnetic circuit theory. And we compared this result with finite element magnetic field analysis result. Based on the actuator model, we made a simulation model of the thrust magnetic bearing system. We showed the closed loop transfer function and sensitivity function of the thrust magnetic bearing system using both the simulation model and the experiment. The experimental result at rotation velocity 18,000rpm of thrust magnetic bearing system is included.

AC Loss Prediction in BSCCO-Tape Armature Winding Design of a Synchronous Motor

A permanent-magnet synchronous motor with high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconducting (HTS) armature operated at sub-cooled liquid nitrogen temperature has been designed. The prototype model has a ten-pole rotor and twelve sets of armature windings which are fabricated with BSCCO tapes, and its output power is 400 kW at the rated speed of 250 rpm. In order to decrease the AC loss of HTS coils to an appropriate level, the conventional stator iron cores are adopted. The coil design, behaviors of HTS conductors, even cooling system design will be proved in the armature case. And the prediction of AC loss in stacked tape conductor exposed to external magnetic fields with various directions have been carried out using FEA method. Based on the 3D magnetic field finite element analyses, this paper presents an AC loss analysis method for the armature winding and provides upper the limit of operating temperature for the cooling system.

A Quantitative Comparative Analysis of a Novel Flux-Modulated Permanent-Magnet Motor for Low-Speed Drive

A novel low-speed flux-modulated (FM) permanent-magnet (PM) motor that breaks the traditional design rule, which stipulates that the number of stator pole pairs and the number of rotor pole pairs must be the same, is proposed. The FM motor has a special physical structure with iron segments in the air gap to modulate the magnetic field. In the design, the free space between adjacent stationary iron segments also acts as ventilating ducts to help improving the heat dissipation and ventilation of the motor. Its cogging torque is very small. In this paper, a rule for comparing the power density of electric motors is proposed. The performance of the FM motor is compared with those of a magnetic-geared PM motor, a traditional PM motor, and a fractional-slot PM motor by using magnetic field finite-element analysis.

Current waveform distortion of doubly‐fed generator for wind turbine application by spatial higher harmonics

AbstractThis paper describes a method to analyze higher harmonic currents resulting from higher space harmonics, depending on the winding pattern of a doubly‐fed generator. A 1.5‐MW generator was used for the analysis, and the results are compared using finite element magnetic field analysis and measurements.The result revealed that the proposed analysis, which focuses on the winding pattern and takes into account higher space harmonics, allows us to calculate higher harmonic currents at high precision, understand the mechanism of changing higher harmonic currents due to the slip or the load of the generator and considerably reduce higher harmonic currents at the armature by restricting higher harmonic currents at the magnetic field. In addition, the sensitivity analysis of design parameters clarified the relationship between current distortion and basic characteristics on electric designs. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 79–85, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20606

Influence of inductance variation on performance of a permanent magnet claw pole soft magnetic composite motor

Winding inductance is an important parameter in determining the performance of electrical machines, particularly those with large inductance variation. This paper investigates the influence of winding inductance variation on the performance of a three-phase three-stack claw pole permanent magnet motor with soft magnetic composite (SMC) stator by using an improved phase variable model. The winding inductances of the machine are computed by using a modified incremental energy method, based on three-dimensional nonlinear time-stepping magnetic field finite element analyses. The inductance computation and performance simulation are verified by the experimental results of an SMC claw pole motor prototype.

A unified discrete model for PWM switching DC to DC converters with current-mode control

This paper presents a unified discrete model for pulse-width modulated (PWM) switching DC to DC converters. The major achievement is that, without any topology modification, the proposed model can be used for performance analysis of the buck, boost and buck-boost converters with any of the two current-mode controls: peak current-mode control and average current-mode control. Three important factors are considered: parasitical effects of circuit elements, non-linear inductance dependent on the current flowing through it, and control time delay, such that the accuracy of performance prediction is greatly improved. Magnetic field finite element analysis (FEA) is conducted to calculate the non-linear differential inductance. By implementing the proposed model into Matlab/Simulink, a simulation model is built. The model has been used for the performance analysis of an existing flyback converter with the peak current-mode control. The simulation results are in good agreement with the actual performance, validating the proposed model.

Parameter Determination And Performance Analysis of a Permanent Magnet Synchronous Generator By Magnetic Field Finite Element Analysis

This paper presents the accurate determination of key parameters and performance analysis of a permanent magnet synchronous generator (PMSG) by finite element magnetic field analysis, providing a sound basis for the machine design and optimisation. Parameters such as the winding flux, back electromotive force and inductances are accurately calculated based on a series of numerical field solutions and improved formulations. An equivalent electrical circuit is employed to derive the equation of the external characteristic, the most important performance of the synchronous generator. The theoretical calculations and analyses have been validated by the experimental results on the PMSG prototype.

Optimal Motor Design Based on a Combination of Non-Linear Programming and Finite Element Magnetic Field Analysis

Optimal Motor Design Based on a Combination of Non-Linear Programming and Finite Element Magnetic Field Analysis

Accurate determination of parameters of a claw-pole motor with SMC stator core by finite-element magnetic-field analysis

Effective and accurate prediction of key motor parameters, such as winding flux, back electromotive force, inductance and core losses, is crucial for design of high-performance motors. Particularly, for electrical machines with new materials and nonconventional topology, traditional design approaches based on the equivalent magnetic circuit, empirical formulas and previous experiences cannot provide correct computation. The paper presents accurate determination of major parameters of a three-phase three-stack claw-pole permanent-magnet motor with a soft magnetic composite (SMC) stator core by finite-element analysis of the magnetic field. The effects of magnetic saturation and armature reaction are considered. The theoretical results by numerical analysis are validated by the experiments on the claw-pole SMC-motor prototype.

有限要素法によるＭＩＧヘッドの非線形磁界解析

Finite element magnetic field analysis is one the best tools for designing magnetic recording heads and arriving at a better understanding of the various phenomena associated with them. This paper describes the modeling of a metal-in-gap(MIG) magnetic recording head using the 2-D finite element method, and various analyses carried out on the basis of this modeling. It was confirmed that an MIG head, owing to the effect of its metallic layer, generates a much steeper magnetic field gradient than a ferrite head and alleviates the saturating characteristics of the magnetic field in relation to the magnetomotive force. The optimized thickness of the metallic layer deposited on one side of the gap is 0.4-1.0μm for a frequency lower than 10 MHz.

Numerical Simulation Of No-Load And Short Circuit Tests For Induction Motors

This paper focuses on the numerical simulation of no-load and short circuit tests in order to estimate parameters of the conventional induction motor equivalent circuit. The proposed model is based on a 2D finite element magnetic field analysis. Particular attention is devoted to the choice of the most suitable simplifying assumptions, also evaluating their influence on the result accuracy. In no-load simulation the current density is imposed and the rotor is kept in a fixed position; magnetizing inductances and iron loss resistances are evaluated. In short circuit test conditions a voltage-driven formulation, including slcin effects, is employed. Leakage inductances and rotor resistances are deduced; after the field solution, 3D effects are taken into account using classical correction factors. The computation technique is applied to several squirrel cage induction motors, and a satisfactory agreement with the measures is found.

An Accelerated Newton-Raphson Technique for Finite Element Analysis of Magnetic Fields in Electrical Machines

An accelerated (modified) Newton-Raphson technique is presented. The new method reduces the computational (CPU) time required to carry out a finite element magnetic field analysis in saturated electrical machines by up to about 60% of typical CPU times required by present state of the art methods. In order to illustrate practical use of the method, the technique is applied to the problem of field determination in a 6-pole, 18 slot, samarium cobalt permanent magnet brushless dc motor system rated at 120 Volt, 15 hp (11.2 KW). The investigated cases include overloads of more than 4 times the rated armature current, thus insuring a substantial degree of magnetic saturation throughout the flux paths in the stator (armature) teeth and yoke. Numerical results of the field solution and armature winding inductances obtained using this method are compared with those obtained using the standard state of the art Newton-Raphson method. It is found that practically no numerical errors are introduced as a result of use of this accelerated Newton-Raphson process. Meanwhile, substantial savings can be made in the computation cost incurred for such analysis, particularly in computer-aided design situations in which large numbers of field solution cases are often required.

FEM input data reduction: An automatic procedure for mesh building in magnetic field studies

An automatic procedure is presented for implementing Finite Element magnetic field analysis techniques in the design of electric machines, transformers and related devices. By means of the Boundary Element Method , a mesh is obtained for studying the magnetic field in a given region by the Finite Element Method. In this way , input data can be reduced and more accurate final data acquired on the region considered, while ensuring a big decrease in program run-time (if an FE iterative procedure is used). The advantages of the procedure are illustrated by its application to a transformer. Comparison of the magnetic field values obtained by the proposed procedure and those by the classical Finite Element Method reveals better agreement with measured values in the case of the former and a 20% reduction in program run-time.

Interactive Computer Graphics in Magnetic Field Analysis and Electric Machine Design

Procedures are described for implementing finite element magnetic field analysis techniques in the design of electric machines, transformers, and related devices. The implementation is aimed at a rapid-response, low-cost intelligent graphics terminal. By means of interactive commands communicated via the graphics screen or terminal keyboard, designers can solve two-dimensional field problems involving saturable materials, and to produce graphs, curves, and flux plots, as well as to compute numeric results. Either black and white or color can be used. The objective of this work is to make the finite element method an engineering design tool easy to use in practical situations, rather than to present a new mathematical formulation.