Permanent Magnet Linear Machine Research Articles

Design and Analysis of an Improved Tubular Permanent Magnet Linear Machine with a T-type Magnet Array

Design and Analysis of an Improved Tubular Permanent Magnet Linear Machine with a T-type Magnet Array

Design and Quantitative Analysis of Asymmetric Flux Reversal Permanent Magnet Linear Machine with Reduced Leakage Flux

Design and Quantitative Analysis of Asymmetric Flux Reversal Permanent Magnet Linear Machine with Reduced Leakage Flux

Investigation and Comparative Study of Double-Sided Yokeless Asymmetric Flux Reversal Permanent Magnet Linear Machine

Investigation and Comparative Study of Double-Sided Yokeless Asymmetric Flux Reversal Permanent Magnet Linear Machine

Investigation and Comparative Study of Double-Sided Yokeless Asymmetric Flux Reversal Permanent Magnet Linear Machine

Investigation and Comparative Study of Double-Sided Yokeless Asymmetric Flux Reversal Permanent Magnet Linear Machine

Novel Virtual Winding Current Controller for Suppression of Linear Permanent Magnet Machine Electromagnetic Thrust Ripple

Thrust force ripple, including no-load detent force and electromagnetic thrust ripple, worsens the precision of linear permanent magnet machine (LPMM) control system. Asymmetrical current injection algorithm has been proposed for the suppression of electromagnetic thrust ripple, and the key point of the algorithm is positive- and negative-sequence (PNS) current closed-loop control. To achieve better steady-state and dynamic performance, a novel high-bandwidth current controller is proposed in this paper. A dual three-phase control system composed of three-phase virtual winding and the three-phase LPMM is introduced. According to the dual three-phase topology, PNS components are decoupled by a novel coordinate transformation, and the proposed controller avoids the use of filters or sophisticated algorithms for extraction of PNS currents. Experimental results based on a linear vernier permanent magnet machine (LVPMM) are presented. It verifies that the asymmetrical current control strategy based on the novel PNS current controller reduces electromagnetic thrust ripple by more than 60% compared with symmetrical three-phase current control.

Design and Analysis of Double-Sided Flux Concentrated Permanent Magnet Linear Machine With Saturation Relieving Effect

This paper proposes a double-sided flux concentrated permanent magnet linear machine (DS-FCPMLM) with saturation relieving effect. With the adoption of slot PMs, DS-FCPMLM can effectively relieve the primary saturation and greatly improve the thrust force density. First, the machine topology and operation principle are introduced. Then, the flux generation mechanism under dual PMs and complementary structure is analytically calculated based on magnetomotive force-permeance model, and further verified by finite element analysis. In addition, some electromagnetic performances including open-circuit characteristic, thrust force performances, demagnetization risk and power factor are comparatively studied. With the help of slot PMs, DS-FCPMLM can significantly improve the thrust force density by 63.4% compared with that only has yoke PMs, and the overload capability can be extended to nearly 4 times of the rated value. More importantly, DS-FCPMLM only consumes 1/30 PM volumes while can achieve 72.2% thrust force density compared with conventional PMLMs for a long stroke with 10 meters. Finally, a prototype of the DS-FCPMLM is carried out for experimental validation.

Design and Optimization of an Improved T-shape Linear Permanent Magnet Machines

Design and Optimization of an Improved T-shape Linear Permanent Magnet Machines

Optimization design of Tubular Permanent Magnet Linear Generator based on entropy model for wave energy conversion

—The effective use of wave energy which has huge reserves is one of the ways to solve the climate problem and energy crisis. In this paper, a Tubular Permanent Magnet Linear Generator (TPMLG) is optimized by the combination of comprehensive sensitive parameters method and particle swarm optimization based on entropy model (EPSO). By introducing the information entropy model, the aggregation characteristics in the process of particle swarm search are accurately analyzed, which can effectively reduce the invalid iteration of particle swarm. Firstly, the main design parameters of TPMLG are designed using the basic initial principle of permanent magnet linear machines. Then, the two-dimensional parametric finite element analysis model of the TPMLG is established, and a comprehensive sensitivity index Sc is defined to calculate the sensitivity indices according to power density and thrust fluctuation. The strong sensitivity parameters are optimized Particle Swarm Optimization based on entropy model, and the Non-sensitivity parameters maintain the initial design values. Finally, an experimental prototype TPMLG was manufactured according to the optimized results. The speed of TPMLG was simulated by the universal testing machine MTS100kN, the experimental results show that the designed TPMLG can be effectively applied to the direct drive power take-off system.

Enhanced Electric Motors Using Multi-Functional 3D Printed Winding With Integrated Heat Sinks

Electrical machines are the central components of many energy conversion systems. Developing the performance of these devices is critical for improved energy management in our society. A new generation of electrical equipment has been enabled by the recent development of additive manufacturing (AM) technologies. This research takes advantage of the greater design freedom given by such approaches to enhance the heat dissipation qualities of the machines in two aspects. Firstly, varying-thickness windings fill up the available space leading to a reduced winding resistance so that the Joule losses can be decreased. Secondly, a novel design of a multi-functional 3D-printed winding is presented. This innovative design accomplishes self-cooling capabilities by including heat sinks into the end-winding. It is achieved by extending the heads of the coils from each turn extremity, creating heat sinks as part of the winding itself. The heat can be extracted directly from the coils to the ambient environment without intermediate pieces. The suggested approaches reduce heat generation and improve heat transmission, allowing for a higher input current. This results in machines with larger power densities for the same volume of permanent magnets while keeping passive cooling. We study a linear coreless permanent magnet machine to explore the concept. Nevertheless, this approach can be applied to different types of electrical machines possibly accommodating other cooling methods.

A novel tubular High-Power-Factor Transverse-Flux linear machine with Concentrated-Flux teeth

Due to principle constraints of the conventional transverse flux permanent magnet linear machine, its PM utilization is less than half. Besides, the complex structure and the serious magnetic leakage also lead to the limited thrust increase and the sharp decline of power factor. Therefore, the high-power-factor transverse-flux permanent-magnet linear machine (HPF-TFPMLM) using the concentrated-flux teeth is proposed in this paper. First, the topology and operation principle of the circumferentially distributed HPF-TFPMLM are investigated. The concentrated-flux teeth and multi-unit concentrated windings are introduced to improve power factor of the HPF-TFPMLM. To further study the proposed HPF-TFPMLM, its counterpart of the axial distributed topology is proposed for comparative analysis. Then, the key electromagnetic performance of power factor, thrust and thrust density of the HPF-TFPMLM are analyzed. Its performances including no-load EMF, magnetic field distribution and overload capacity are evaluated and compared with its counterpart. Finally, the feasibility and correctness of the investigated HPF-TFPMLM are verified.

Developments of Prototype Automatic Transportation Lines with a Direct Electric Drive

The increasingly demanding requirements for the production capacity, accuracy and repeatability of industrial production require the development of fully automated transportation lines in which a workpiece is mounted once and passes all stages of the technological process. To solve these problems, the leading manufacturers of machinery construction equipment offer, instead of conveying systems with belt or roller drive, modular automatic transportation lines based on direct drives with permanent-magnet linear synchronous machines. A specific feature of using a linear machine in a transportation line is an inverted mutual layout of the primary part (the armature) and the secondary part (the magnetic way) in which the magnetic way segment moves over a number of modules distributed along the line with a set of armatures and sensors controlled by individual servo amplifiers interconnected by a digital bus. With such solution, a workpiece is attached to the passive moving part that does not require the connection of electrical cables – to ensure its free and independent movement within the entire production line. The modularity of the design provides flexibility of the transportation systems. The article gives a review of solutions offered by various manufacturers, shows the specific features of using linear synchronous machines and sensors in such systems, and proposes the authors’ own developments of prototype transportation lines.

Analytical Modeling of Magnetic Field Distribution at No Load for Surface Mounted Permanent Magnet Machines

This paper presents an analytical study of the air-gap magnetic field of a Surface Permanent Magnet (SPM) linear machine under no load. By means of the method of images, the complex expression of the magnetic field of a conductor, inside the air gap between two smooth iron surfaces, is retrieved. Then, integrating the conductor expression, the formulation of the magnetic field of a current sheet and thus the one of a SPM, using two vertical current sheets, is obtained. At last, the no-load magnetic field expression, for a generic time instant, of a slotless machine is retrieved. The novelty of the proposed approach is the availability, due to a different calculation approach, of a unique closed-form formulation for the slotless machine air-gap field, a quantity that, in literature, is usually present in Fourier series formulation. Additionally, as a means to calculate integral quantities and show the goodness of the method a complex slotting function is introduced to account for the slotted geometry. Finally, starting from Lorenz’s force formulation, the expression of the Maxwell tensor in complex form is retrieved and the contribution of forces, integral of the complex stress tensor quantity, will be calculated and compared with FEM simulations, showing a good agreement also with the analytical slotted model.

Novel Partitioned Stator Flux-Switching Permanent Magnet Linear Machine: Design, Analysis, and Optimization

Over the past few decades, flux-switching permanent magnet (FSPM) machines have gained more attention. A novel flux-switching permanent magnet linear machine with a partitioned stator (FSPMLM-PS), which has the advantages of high thrust force density and high cost efficiency for short-stroke applications, is presented and analyzed in this article. Firstly, the twelve mover slots and seven stator poles (12s/7p) structure of FSPMLM-PS is introduced, and the fundamental principle of operation is investigated. The partitioned stator helps with the reduction in iron losses and the overall cost of the proposed FSPMLM-PS. One of the frequent issues in linear machines is the end effect, which is compensated for by setting assistant teeth at both ends of the mover. The proposed machine’s main design specifications are globally optimized through a multiobjective genetic optimization algorithm using JMAG software ver. 16.1, although the volumes of the PM and the magnetic and electric loadings are kept the same. The peak-to-peak flux linkage, thrust force, thrust ripples, and detent force are improved by 26.98%, 27.98%, 22.03%, and 68.33%, respectively, after optimization. The comparison results show that the proposed FSPMLM-PS is preferable to the conventional FSPMLM given in the literature. Under the same PM volume, the proposed machine provides 27.95% higher thrust force density.

Electromagnetic Characteristics of a Flux-Modulated Permanent Magnet Linear Machine With Sandwich Armature for Free-Piston Energy Converter System

The linear machine is the key part of free-piston energy converter system, and its electromagnetic characteristics directly determine system performance. This paper proposes a novel flux-modulated permanent magnet (PM) linear machine with sandwich armature for free-piston energy converter system. The sandwich armature is composed of modulated layer, air-core winding layer and iron core. It integrates electromagnetic advantages of a flux-modulated and slotless machine, so it can achieve good comprehensive performance by appropriate design of sandwich armature. Firstly, an accurate subdomain model is established to analyze magnetic field characteristics of proposed machine, and then the suitable pole/slot combinations are determined. Subsequently, machine performance such as thrust force and efficiency are discussed based on design dimensional constraints. Finally, structural optimization of cylinder armature is developed for eddy-current loss suppression, and then experiments on prototype are carried out. The performance comparisons with flux-modulated and slotless machines show that the proposed prototype has high peak thrust, small electromechanical time constant, and strong design flexibility. Hence it is a preferred solution for free-piston energy converter system.

A Comprehensive Review on the End Effects of Linear Permanent Magnet Machines

This article presents a literature review of relevant contributions found in the literature concerning the end effects with a focus mainly on linear permanent magnet synchronous machines. Additionally, it presents a classification of the obtained information to classify the end effects and provides essential information for understanding, categorization, modeling, mitigation, and control of the end effects. The causes and consequences of the end effects are also addressed according to the geometrical structure of the linear machine, and the main approaches for end effects modeling are discussed. Also, several existing techniques for mitigation of consequences of end effects are presented, considering changes in the machine geometry or the electromagnetic structure and electronic compensation using control techniques. The control of linear machines accounting for end effects and compensation to achieve better performance to mitigate adverse impacts on machine characteristics are also addressed.

Introduction to Mesh Based Generated Lumped Parameter Models for Electromagnetic Problems using Triangular Elements

This paper is an introduction to mesh based generated reluctance network modeling using triangular elements. Many contributions on mesh based generated reluctance networks using rectangular shaped elements have been published, but very few on those generated from a mesh using triangular elements. The use of triangular elements is aimed at extending the application of the approach to any shape of modeled devices. Basic concepts of the approach are presented in the case of electromagnetic devices. The procedure for coding the approach in the case of a flat linear permanent magnet machine is presented. Codes developed under MATLAB environment are also included.

Nonlinear Semianalytical Model for Axial Flux Permanent-Magnet Machine

In this article, we propose a novel nonlinear semianalytical model (AM) for the magnetic field calculation of electric machines. The nonlinear properties and local saturation effect of the iron part are taken into consideration in Cartesian coordinates, which is the main contribution of the proposed model. Thus, high accuracy of electromagnetic field results can be obtained with the low computational time cost. The model is developed based on the harmonic modeling technique by solving Maxwell's equations. The detailed theoretical derivations, which use the complex Fourier series and the Cauchy product, are presented. To verify the proposed model, an axial flux permanent-magnet (PM) machine is selected to be investigated. Both finite-element model and experimental results agree well with that of the proposed model. Moreover, the nonlinear AM has potential application for other types of PM electrical motor in Cartesian coordinates, such as flat PM linear machines.

Two-dimensional Harmonic Modelling for Electro-magnetic Solution in Cartesian Coordinates

This paper first presents a general two-dimension (2D) harmonic analytical solution for the magnetic field of electric machines in the Cartesian coordinates. In this solution, the relative permeance is directly considered in Laplace and Poisson’s equations, and the particular solutions in Cartesian coordinates are solved. By applying the complex Fourier separation method, with the boundary and interface conditions, the magnetic field in the inhomogeneous region is solved from system equations. Numerical examples validate the presented method and the obtained results have a satisfactory agreement with the finite element analysis. The proposed model in this paper has a significant value for modelling electric machines, such as linear permanent magnet (PM) machines and axial flux PM machines.

Design of a 120 W Electromagnetic Shock Absorber for Motorcycle Applications

Based on the shock absorber size and power and power density limitations in motorcycle application, a linear permanent magnet machine for a regenerative suspension system that recovers the kinetic energy originating from shock absorber vibration is investigated. To achieve the target power of 120 W, several design parameters were investigated. The eight-slot eight-pole combination was used due to its high power density. A hybrid permanent magnet structure was implemented which was a combination of a classical Halbach array and iron spacers. In addition, the dimensions of the permanent magnet, and stator inner radius were parametrically studied to enhance the air-gap flux density and coil volume, which are the main factors affecting performance. The detailed design generated 124 W of average power under the rated condition, assuming a vibration speed of 0.157 m/s. Despite the satisfaction of the output power and power density, the large magnetic force caused by the interaction between the iron core and permanent magnet is the main drawback of this design, which has a negative impact on driving safety and comfort. To commercialize the suggested device, additional studies will focus on size, electromagnetic reduction, as well as road test performance.

Design optimization of a novel linear transverse flux switching permanent magnet generator for direct drive wave energy conversion

Linear transverse flux permanent magnet machines (LTFPMs) are categorized as high force density topologies, which are suitable candidates for direct drive and low-speed applications. This paper introduces a novel LTFPM topology, which also proposes advantages of the flux-switching machines. This proposed linear transverse flux switching PM machine (LTFSPM) has two long passive translators located at the armature's top and bottom sides. The topology offers a high value of force density, and also, it is a cost-effective topology due to its double-sided passive translator. Furthermore, the PMs are fully utilized in the magnetic circuit, the end winding length is negligible, and the iron cores can be laminated easily. In this paper, the operation principle of the topology is explained and its magnetic circuit is discussed. To reduce the computational time of optimization procedure, a double-layer method is adopted, which provides high robustness, low computational time, and high precision. Results of the finite element method indicate that the proposed machine can be considered a potential candidate for linear motion applications especially direct drive wave energy conversion systems, which require high force density values.