Finite Element Magnetic Field Research Articles

Loss Calculation Method Considering Hysteretic Property With Play Model in Finite Element Magnetic Field Analysis

This paper proposes a novel estimation method for iron loss considering hysteretic property. In the proposed method, iron loss considering hysteretic property is estimated with play model as a postprocessing of usual finite element magnetic field analysis based on ordinary magnetization curve. Numerical results are compared with measured results to demonstrate the effectiveness of the proposed estimation method for iron losses.

Performance Analysis of a Linear Motor with HTS Bulk Magnets for Driving a Prototype HTS Maglev Vehicle

This paper presents the performance analysis of a linear synchronous motor which employs high-temperature superconducting (HTS) bulk magnets on the mover and normal copper windings on the stator. The linear motor is designed to drive a prototype HTS maglev vehicle in which the mover is suspended by the levitation force between HTS bulks on the mover and permanent magnets on the ground. Finite element magnetic field analysis is conducted to calculate the major parameters of the linear motor and an equation is derived to calculate the electromagnetic thrust force. Theoretical calculations are verified by the measured results on the prototype.

WE‐G‐WAB‐07: Commissioning of a Novel Integrated Platform for Online MRIgRT

Purpose: An integrated system for online MRIgRT comprising an MR scanner‐on‐rails proximal to a Varian TrueBeam linac is currently under installation at our institution. This study presents the development of a procedure to commission this platform along with the synthesis, testing, and validation of several unique tools/methods central to this challenging frontier. Methods: The commissioning procedure is organized into three phases: 1) the linac and a modified patient couch are commissioned in the absence of magnetic fields; 2) the MR magnet is energized, followed by experimental field mapping and verification of linac/couch performance proximal to the magnet; 3) MR imaging is evaluated and integrated guidance functionalities are tested. Novel methods/technologies embedded in these steps include: magnetic field finite element simulations to confirm magnetic decoupling of the MR scanner, linac, and couch; development of a novel harmonic distortion analysis/shim evaluation technique and associated phantom design incorporating comprehensive imaging QA; simulation of patient‐induced susceptibility distortions and pulse sequence optimization; development of a phantom/method to evaluate the accuracy/stability of MR scanner/couch travel. Results: The finite element simulations of the MRIgRT platform indicated acceptable magnetic forces on critical couch/linac components, undisturbed x‐ray beam production, and acceptable field uniformity within the MRI active volume (via active shimming). Validation of the harmonic distortion analysis demonstrated that complete volumetric mapping of the geometric distortion could be performed with an error bound by the imaging voxel size. Susceptibility‐induced distortions were simulated for various anatomical sites and can be reduced to within 1–2 mm by increasing the frequency encoding gradient strength with acceptable SNR losses. Lastly, the accuracy of translation and rotation measurements was established for evaluating MR scanner/couch travel. Conclusion: A comprehensive procedure has been established for the commissioning of an integrated MRIgRT platform, and various key tools/methods for assessing system performance have been developed and tested. J. Winter and L. Petropoulos are employees of IMRIS. J. Marle and M. Sweitzer are employees of Varian Medical Systems. IMRIS and Varian are companies co‐developing the MRgRT system. Funding for the MRgRT project at Princess Margaret Hospital was provided by the Canadian Foundation for Innovation.

A fault-tolerant triple-redundant voice coil motor for direct drive valves: Design, optimization, and experiment

A direct drive actuator (DDA) with direct drive valves (DDVs) as the control device is an ideal solution for a flight actuation system. This paper presents a novel triple-redundant voice coil motor (TRVCM) used for redundant DDVs. The TRVCM features electrical/mechanical hybrid triple-redundancy by securing three stators along with three moving coils in the same frame. A permanent magnet (PM) Halbach array is employed in each redundant VCM to simplify the system structure. A back-to-back design between neighborly redundancies is adopted to decouple the magnetic flux linkage. The particle swarm optimization (PSO) method is implemented to optimize design parameters based on the analytical magnetic circuit model. The optimization objective function is defined as the acceleration capacity of the motor to achieve high dynamic performance. The optimal geometric parameters are verified with 3D magnetic field finite element analysis (FEA). A research prototype has been developed for experimental purpose. The experimental results of magnetic field density and force output show that the proposed TRVCM has great potential of applications in DDA systems.

Finite Element Analysis and Experimental Study for MWD Hybrid Excitation Generator

To obtain the stable output voltage, a new type of MWD hybrid excitation generator is designed in which magnetic flux can be regulated from -2% to 22%. In the generator, hybrid excitation part and permanent magnet part work in parallel. This article introduces the working principle and structure of this generator. In addition, finite element analysis, magnetic field and regulation characteristics analysis for this generator is addressed to illustrate the variation of magnetic flux with pole length and excitation current changing. Experiments verify the design and finite element analyses.

The Study of 3-D Magnetic Field Finite Element Analysis for Giant Magnetostrictive Actuator

Based on the structure and working principle of our giant magnetostrictive actuator (GMA), the properties of the driving magnetic field were researched. A 3-D nonlinear magnetic field model of the GMA was established with the finite element analysis method, and the magnetic field distribution of the GMA was obtained with the software ANSYS. Then the 3-D model helped us to find the effects about the distribution of magnetic field of the GMA from the structure. The 3-D magnetic field finite element analysis model can give us a new tool of GMA design and analysis.

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.

A Parameterized Mesh Technique for Finite Element Magnetic Field Computation and Its Application to Optimal Designs of Electromagnetic Devices

A parameterized mesh generation is presented for design optimization of electromagnetic devices. The proposed method requires no mesh regeneration, and hence the numerical simulation time can be reduced significantly. When the coordinates of nodes in the refined mesh are changed, the mesh topology will be kept, that is, the node connection relationship will remain the same as before. Thus the nodal solutions can be carried over from previous FEM results to subsequent FEM computation without the need of mapping the nodes between two meshes. Additionally, the mesh quality can remain high using a swapping diagonal technique. Based on the sample points obtained from FEM with parameterized mesh, the optimal model is reconstructed using the response surface methodology (RSM). The particle swarm optimization (PSO) method is then used to arrive at the optimal solution swiftly and efficiently. An optimal design of electromagnetic device is reported to verify the efficiency and effectiveness of the proposed method.

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.

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

Implementation of an Anisotropic Vector Hysteresis Model in a 3-D Finite-Element Code

The implementation of a vector hysteresis model in 3-D finite-element magnetic field calculation is performed. The vector model is derived from the original scalar Jiles-Atherton one. The hysteresis model has been implemented in a 3-D vector potential formulation. The nonlinear equation system is solved using the Newton-Raphson method. A comparison between measured and calculated results is performed.

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.

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.

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.

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

Transient finite element magnetic field calculation method in the anisotropic magnetic material based on the measured magnetization curves

A lot of magnetic materials are anisotropic. In the 3D finite element method calculation, anisotropy of the material is taken into account. Anisotropic magnetic material is described with magnetization curves for different magnetization directions. The 3D transient calculation of the rotational magnetic field in the sample of the round rotational single sheet tester with circular sample considering eddy currents is made and compared with the measurement to verify the correctness of the method and to analyze the magnetic field in the sample.

Novel bidirectional linear actuator for electrohydraulic valves

This paper presents a permanent-magnet actuator with bidirectional and high levels of linear force over short strokes. The actuator can be used in electrohydraulic valves. Its static and dynamic performances were analyzed by using two-dimensional finite-element magnetic field solutions that take into account the nonlinearity of the material. The measured and simulated results are highly consistent. Experimental results show that the prototype actuator can produce a force of /spl plusmn/60 N, its nonlinearity is less than 0.5%, and the hysteresis is less than 2% within a stroke of /spl plusmn/1 mm. The actuator's frequency response (-3 dB) can reach 150 Hz.

Characteristic Analysis and Modification of PM-Type Magnetic Circuit Breaker

This paper presents the operating characteristic analysis of a permanent magnet (PM)-type magnetic circuit breaker using the two-dimensional finite-element magnetic field solution, taking into account nonlinearity of the material and the eddy current. The effect of the eddy current on the dynamic characteristic of the breaker is analyzed from the finite-element analysis. A new modified model to decrease the eddy current is proposed. The characteristics of the two models are compared.