Magnetic End Effects Research Articles

Modeling of Current-Driven End-Effect Force Ripple in Air-Cored Linear Synchronous Motor With Multiple Modular Stators

This paper presents a segmented layer model (SLM) for the air-cored linear permanent-magnet synchronous motors (LPMSMs) with multiple modular stators. In the LPMSM with modular stators, the significant current-driven ripples (CDRs) are observed as the PM mover moves across the stator modules, due to the magnetic end effects. Such CDRs become more severe as the current excitation level increases. In order to correctly model the overall motor forces in the LPMSM, the analytic motor model needs to be able to capture the magnetic end effects from both the stator and mover, and also include the current-driven effects. The SLM method presented in this paper divides the analytical region into several segmented layers to be able to accurately capture both the geometric-saliency- and current-driven force ripples by using layers with different fundamental spatial frequencies. The fidelity of the proposed SLM is validated both by the finite element method (FEM) and the experiments. The SLM achieves an accuracy of more than 97 % and 87 % compared to the FEM and experimental results, respectively, while reducing the computation time by two orders of magnitude as compared to the FEM.

Influence of end-effect and end-winding on the electromagnetic losses and efficiency in high speed permanent magnet machines

<span>Permanent-magnet excitation machines (SPMMs) having mounted magnet on the outer surface of their rotor are preferred for high speed applications such as turbochargers, mechanical turbo-compounding systems, racing engines and fuel pumps, over other types of machines including induction and switched-reluctance machines, since the SPMMs integrate the features of high torque density, compact rotor structure, high reliability and simple structure. However, in the SPMMs, due to the need for a retaining sleeve for the rotor, a large magnetic airgap results and consequently a large magnet thickness is required, hence the magnetic end-effect is relatively high. On the other hand, the use of an overlapping distributed winding leads to a significantly large end-winding length. Hence, the end-effect and the end-winding influences on the performances of a high-speed SPMM is considered in this paper. With a view to get the impact of the end-effect, a comparison between three-dimensional (3D-FEA) results and counterparts two-dimensional finite element analyses (2D-FEA) have been conducted. Results show that, higher efficiency at low torque and low speed due to the low electromagnetic losses and at high speeds due to the high flux-weakening capability are seen when the influences of end-effect as well as end-winding are taken into account.</span>

Numerical analysis of liquid flows exposed to travelling magnetic field. 2. MHD instabilities due to magnetic end effects

Numerical analysis of liquid flows exposed to travelling magnetic field. 2. MHD instabilities due to magnetic end effects

Improved 3D electromagnetic analytical model for planar induction heater with consideration of transverse edge effects

PurposeThis paper aims to propose a new 3D electromagnetic model to compute translational motion eddy current in the conducting plate of a novel linear permanent magnet (PM) induction heater. The movement of the plate in a DC magnetic field created by a PM inductor generates induced currents that are at the origin of a heating power by Joule effect. These topologies have strong magnetic end effects. The analytical model developed in this work takes into account the finite length extremity effects of the conducting plate and the reaction field because of induced currents.Design/methodology/approachThe developed model is based on the combination of the sub-domain’s method and the image’s theory. First, the magnetic field expressions because of the PMs are obtained by solving the three-dimensional Maxwell equations by the method of separation of variables, using a magnetic scalar potential formulation and a magnetic field strength formulation. Then, the motional eddy currents are computed using the Ampere law, and the finite length extremity effects of the conducting plate are taken into account using the image’s method. To analyze the accuracy of the proposed model, the obtained results are compared to those obtained from 3D finite element model (FEM) and from experimental tests performed on a prototype.FindingsThe results show that the developed analytical model is very accurate, even for geometries where the edge effects are very strong. It allows directly taking into account the finite length extremity effects (the transverse edge effects) of the conducting plate and the reaction field because of induced currents without the need of any correction factor. The proposed model also presents an important reduction in computation time compared to 3D finite element simulation, allowing fast analysis of linear PM induction heater.Practical implicationsThe proposed electromagnetic analytical model can be used as a quick and accurate design tool for translational motion PM induction heater devices.Originality/valueA new 3D analytical electromagnetic model, to find the induced power in the conducting plate of a novel translational motion induction heater has been developed. The studied heating device has a finite length and a finite width, which create edge effects that are not easily considered in calculation. The novelty of the presented method is the accurate 3D analytical model, which allows finding the real power heating and real distribution of the induced currents in the conducting plate without the need to use correction factor. The proposed model also takes into account the reaction field because of induced currents. In addition, the developed model improves an important reduction in the computation time compared with 3D FEM simulation.

Investigation of Magnetic End Effects in Amorphous Wires and Ribbons and Simulation of the Resulting Magnetoimpedance

The existing experimental results have shown that the magnetic characteristics of amorphous wires in different length or in different positions at the end are significantly varied. To study the end effect, the magnetic field distribution at the end of amorphous ribbon of infinite-length and finite-width is analyzed by means of conformal mapping. Because the internal magnetic field intensity of the amorphous ribbon is impossible to exceed that of the external, the model of three magnetic zones is proposed, which consists of the magnetic uniform zone in the middle, the magnetic in-zone and out-zone at the two ends. And the formula for calculating the critical length of magnetic end effect is derived. Due to the great difficulty in obtaining the analytic solution of the end magnetic field of amorphous wire, the assumption in the distribution of magnetic charges and the numerical computation method are applied to obtain the magnetic field distributing form at the end of amorphous wire. The three-zone model is also suitable for the distribution of the amorphous wire and its critical length formula of the magnetic end effect can be deduced. Considering the magnetic end effect, a simple simulation modeling method to study the magnetoimpedance of amorphous wires and ribbons is presented based on the fitting magnetization curve and the local magnetization analysis, which can well explain the existing experimental phenomena.

Simulation of magnetic end effect of amorphous wires

The existing experimental results have shown that the magnetic characteristics of amorphous wires with different lengths or of the same amorphous wire at different longitudinal locations are significantly different. To study this effect, the magnetic field at the end of the amorphous wires is obtained by numerical computation method based on the supposed uniform distribution of the magnetic charge. Then, the general formula of the magnetic field inside the amorphous wire is deduced by analyzing the calculation results and using the fitting algorithm. Because the magnetic field intensity inside the wire is restricted by the external magnetic field source, the model of three magnetic zones is proposed, which consists of the zone of uniform magnetic field in the middle of the wire, the magnetic field entrance-zone and exit-zone at the two ends. The critical length of the magnetic end effect can be estimated by a formula derived from the model. The simulation results of the magnetic end effect can satisfactorily explain the existing experiments.

A Geophysical Study of the Red Sea Axial Trough between 20*5 and 22 N

Summary New bathymetric, seismic reflexion, gravity and magnetic data have been obtained in a detailed survey of part of the axial trough in the central Red Sea. These data show that the trough is not continuous, but is broken into two sections separated by a shallow region, called the ‘inter-trough zone’. This zone has a thick sediment cover and is devoid of magnetic anomalies. It may represent a fracture zone into which salt and other sediments have flowed, or it may be a section of spreading axis which has remained covered with sediments for an unknown reason. The transverse magnetic anomalies, previously recognized by Allan, Phillips and other, have been fully mapped, and a further transverse lineation has been discovered. Using three-dimensional computations, a model has been developed which can account for these lineations as the magnetic end effects of a series of short spreading axes offset by closely-spaced transform faults. The development of such a configuration is discussed and can be seen as a natural consequence of the plate geometry in this region.