Double-sided Permanent Magnet Research Articles

Design and Analysis of a Multi-unit Distributed Permanent Magnet Arc Motor Having Double-Sided Permanent Magnet Excitations

Design and Analysis of a Multi-unit Distributed Permanent Magnet Arc Motor Having Double-Sided Permanent Magnet Excitations

DPMSLM Demagnetization Fault Detection Based on Texture Feature Analysis of Grayscale Fusion Image

This study investigates a novel image morphology texture feature extraction method to realize the demagnetization fault location and severity detection of double-sided permanent magnet synchronous linear motor (DPMSLM). Initially, according to the constraints of DPMSLMs topology structure, the three lines magnetic density signal in motor air gap is extracted by finite element analysis as effective fault signal. Then, the grayscale fusion image (GFI) method is introduced to transform 1D data signal to 2D fused grayscale image which can better describe the demagnetization fault information. The unique features are visualized using the image enhancement techniques, and the image morphology texture features such as the area, Euler number, perimeter operator, correlation of binary image and so on can be extracted to constitute the demagnetization fault indexes. In addition, fisher score (FS) is used for feature optimization which can reduce the feature dimension. Furthermore, the two-level multiverse optimization support vector machine (MVO-SVM) algorithm is established to conduct demagnetization fault classification. Comparison experiments with other classifiers show that the MVO-SVM has a high fault identification accuracy of more than 98.3% and low running time less than 2.57s. Finally, the motor prototype experiment results show that the proposed method can accurately identify the location and severity of DPMSLM demagnetization faults, and it is an effective and feasible method which can be applied in DPMLM batch demagnetization inspection before delivery.

Detent Force Minimization of Double-Sided Permanent Magnet Linear Synchronous Machine with 120° Phase Belt Toroidal Windings by Slot-Shift Structure

Double-sided permanent magnet linear synchronous machine with 120° phase belt toroidal windings (120°-TWDSPMLSM) suffers from large detent force due to the end effect and slot effect. Many existing methods can reduce the detent force of the 120°-TWDSPMLSM effectively. But they also minimize the back electromotive force (back-EMF) and thrust simultaneously. To alleviate this problem, this paper adopts a method of combining slot-shift structure with rearranging the 120° phase belt toroidal windings (120°-TW) to suppress the detent force and improve the back-EMF and thrust of the 120°-TWDSPMLSM simultaneously. First, the slots on the two sides of the primary part are stagger by an optimal distance to reduce the detent force. The models of the detent force, including the end force and cogging force, is established theoretically, and then verified by finite-element analysis (FA). Then, the 120°-TW are rearranged to improve the back-EMF and average thrust. And the electromagnetic characteristics of the 120°-TWDSPMLSM under different shifted distances are analyzed and compared in detail. Finally, the result shows that the detent force of optimized machine is 70.19% lower than that of the original machine, and the thrust fluctuation reduces 19.21%. Besides, the back-EMF of optimized machine is 6.84% lower than that of the original machine, but 31.86 higher than the machine with shifting slots and without rearranging the 120°-TW. Therefore, the optimal method in this paper is available in the detent force reduction and thrust improvement of the 120°-DSPMLSM.

Research on Internal and External Split Ratio of Double-Sided Rotor Permanent Magnet Motor Based on Copper Consumption Density and Current Density

In the traditional split ratio optimization of double-sided rotor permanent magnet motors (DSRPMM), the typical thermal constraint condition is that the total copper consumption of the motor is fixed. This method can only constrain the overall temperature rise of the motor to a certain extent, but it is limited to restrain the local short-time heating of the winding. On the basis of the heat dissipation mode and external size of the motor, an optimal design method of the split ratio based on copper consumption density and current density is presented in this paper. The method restricts the whole heating of the motor and the local short-time heating of the winding by limiting the copper consumption density and current density. The thermal is used as the electromagnetic torque boundary. By analyzing the relationship between the electromagnetic torque and the split ratio, the expression of the optimal split ratio based on the maximum electromagnetic torque is derived. The analysis model is established by using the finite element tool, and the accuracy of the expression is proved. Based on the analysis results, a DSRPMM prototype is made and the experimental test is carried out. The experimental results of the prototype demonstrate the accuracy of the optimal design method of the split ratio based on copper consumption density and current density. The research of this paper provides a theoretical basis for improving the accuracy and reliability of the DSRPMM design.

Characteristics Analysis of Double-Sided Permanent Magnet Linear Synchronous Motor with Three-Phase Toroidal Windings

This paper proposes three-phase 120° phase belt toroidal windings (120°-TW) and are applied in a double-sided permanent magnet linear synchronous motor (DSPMLSM), in which the incoming ends of all coils are on the same side and have the same incoming direction. First, the structure of the proposed motor is introduced and its operation principle is analyzed by describing the variation in the armature magnet field versus time. Second, based on the similar volume, magnetic load and electrical load, the initial parameters of the DSPMLSM with different winding arrangements are presented. Then, the finite-element models (FEMs) of the DSPMLSM with 120°-TW (120°-TWDSPMLSM) and traditional toroidal windings (TTW) are established to analyze the distribution of magnetic field, back electromotive force (back-EMF), detent force, thrust, efficiency and so on. Besides, the primary optimization of the detent force is designed. Finally, the results show that the thrust density and efficiency of the 120°-TWDSPMLSM is higher than that of DSPMLSM with TTW (TTWDSPMLSM).

A Novel Track Structure of Double-Sided Linear PM Synchronous Motor for Low Cost and High Force Density Applications

Conventional coreless linear permanent-magnet (PM) synchronous motors have been used commonly in various applications in industry. In this article, coreless double-sided PM linear motor design alternatives are proposed with a novel track structure with less magnets. A linear motor design with conventional coreless PM linear synchronous motor (PMLSM) is provided as a benchmark. Detailed 3-D finite-element analysis simulations for the proposed new track structures are presented with conventional linear motor design data. A thorough performance comparison is also presented. A prototype motor of a promising track design is built and tested. It is shown that the design data and test results are in good agreement, and the proposed alternative track design could be a decent low cost and relatively high force density solution for some applications.

Demagnetization Fault Detection for Double-Sided Permanent Magnet Linear Motor Based on Three-Line Magnetic Signal Signature Analysis

This article investigates a novel demagnetization fault detection method for double-sided permanent magnet synchronous linear motors (DS-PMSLM) that are applied in laser cutting machines. First, a finite-element analysis model of DS-PMSLM is built to preset different demagnetization faults of the permanent magnets (PMs). Second, magnetic intensity distribution signals in air gap region are selected as fault signal for the first time to detect demagnetization faults in DS-PMSLM. Three-line method coupled with self-designed connection structure is originally proposed to obtain and analyze three-line magnetic signals. Simulation comparison with back electromotive force signal validates that three-line magnetic signals are more effective to solve the problem for this double-sided structure PMSLM. Then, continuous wavelet transform (CWT) is innovatively introduced to conduct peak feature extraction for magnetic signals. Comparison experiments between CWT, direct locating method, and polynomial fitting method certify the superiority of CWT. By peak feature analysis, the positions, sides, and severity degrees of PMs' demagnetization faults can be detected accurately. Finally, a prototype is manufactured, and a Gauss meter experimental platform is established to verify the validity and advantages of this method.

Segmented power supply control of double‐sided linear flux‐switching permanent magnet motor

Current research shows that the double-sided linear flux-switching permanent magnet (DLFSPM) motor is suitable for electromagnetic launch systems, in which the armature windings and permanent magnets are set on the long primary stator, whereas the mover is only composed of yokeless iron. Thus, the DLFSPM motor incorporates the merits of high power density and efficiency of the linear permanent magnet synchronous motor and simple and robust structure of linear induction motor. To improve the power factor and decrease the inverter capacity, the segmented power supply control methods of the DLFSPM motor are investigated in this study. First, the structure, electromagnetic parameters, and the segmented power supply method of the DLFSPM motor are explored. Then, the mathematical models and the control strategies of the DLFSPM motor are deduced and proposed. Finally, the simulations and experiments of the DLFSPM motor are conducted to validate the study of segmented power supply method.

Detent Force, Thrust, and Normal Force of the Short-Primary Double-Sided Permanent Magnet Linear Synchronous Motor With Slot-Shift Structure

Phase-shift or pole-shift method can reduce the detent force of the double-sided permanent magnet linear synchronous motor (DS-PMLSM) dramatically. However, this method causes a decrease in thrust and an increase in normal force simultaneously. To overcome this drawback, a novel slot-shift structure whose slots on the two sides of the primary component are staggered by an optimal distance is proposed in this paper. The models of the detent force including the end force and cogging force is established theoretically, and then verified by finite element analysis. The windings in the upper primary and the lower primary are arranged differently to improve the average thrust. The thrust characteristics of the DS-PMLSM under different shifted distances are analyzed and compared in detail. Furthermore, the primary component employing two kinds of core laminations is proposed to reduce both the dc component and ripple of the normal force. Finally, a DS-PMLSM prototype is tested, and the experimental results are compared with the analytical results to verify the effectiveness of the theoretical and simulation research.

A New Demagnetization Fault Recognition and Classification Method for DPMSLM

This paper investigates a new method for the demagnetization fault recognition and classification in double-sided permanent magnet synchronous linear motors that are used in linear motion applications. This method is based on time–time-transform (TT) coupled with extreme learning machine (ELM), which are especially suitable for the industrial occasions such as motor batch demagnetization inspection before delivery and periodic maintenance. First, a finite element analysis model with demagnetization faults is built to extract three lines (up-line, center-line, and down-line) magnetic flux density signals. Second, TT is first applied to conduct magnetic signals waveform transformation, and digital picture processing technology is innovatively used to extract the pixel rate of its diagonal elements contour surfaces as the fault feature. Then, machine learning algorithm called ELM is utilized as a classifier to obtain the unique fault labels that can represent the demagnetization occurred positions, sides, and severity types in detail. The validity and superiority of ELM is verified through comparison with back propagation neural network, and probabilistic neural network. Finally, prototype motor experimental platform is designed to confirm the correctness and effectiveness of this proposed method.

Electromagnetic and Thrust Characteristics of Double-sided Permanent Magnet Linear Synchronous Motor Adopting Staggering Primaries Structure

Traditionally, straggering the primaries of the double-sided permanent magnet linear synchronous motor (DS-PMLSM) is beneficial in helping to reduce the detent force caused by the longitudinal end effect, but leading to a reduction of the average thrust. To overcome this disadvantage, this paper provides a novel DS-PMLSM, which adopts the structure of staggering two primaries and rearranging windings. First, the characteristics of the voltage and detent force are analyzed theoretically and verified by finite element (FEM) simulations. The inductance, thrust, and normal forces are then compared with the traditional DS-PMLSM. Furthermore, the geometrical parameters are optimized to improve the thrust. Finally, one DS-PMLSM prototype is tested. The detent force and back electromotive force tested results verify the effectiveness of the topology proposed in this research.

Detent-Force Minimization of Double-Sided Permanent Magnet Linear Synchronous Motor by Shifting One of the Primary Components

The longitudinal end effect of the double-sided permanent magnet linear synchronous motor (DS-PMLSM) causes a large end force. To overcome this drawback, this paper proposes a novel DS-PMLSM structure, in which the upper or lower primary component is shifted by a certain distance. First, the end-force model of the DS-PMLSM is established, based on which, the influences of the staggered structure on the fundamental and higher order end-force components are analyzed. Following this, the DS-PMLSMs with different slot–pole combinations are divided into four categories, and the design principles of possible winding arrangements are discussed. Furthermore, the staggered structures are applied to four slot–pole combinations, namely 21-, 15-, 20-, and 16-pole/18-slot. The back electromotive forces, detent forces, thrusts, and normal forces of the four combinations are analyzed and compared through the finite-element method. The electromagnetic and output characteristics of the novel DS-PMLSM are also compared with the traditional DS-PMLSM prototype to verify the effect of the proposed structure on suppressing the end force.

Characteristic Analysis and Experimental Verification for a Double-Sided Permanent Magnet Linear Synchronous Generator According to Magnetization Array

This paper compares the characteristics of a double-sided small-scale permanent magnet linear synchronous generator (PMLSG) using three different magnetization arrays. Though PMLSGs generally prefer a parallel array, we propose the Halbach array and an axial array, which are widely used in permanent magnet devices. For an accurate comparison, the output power, mechanical air-gap thickness, and overall size are all equal. On the basis of analytical two-dimensional field solutions, this study predicts magnetic fields, losses, masses, and output powers of the three arrays. The experimental results are validated extensively by comparing them with finite element analysis results. This result shows the best arrangement of a double-sided small-scale PMLSG compared to the experimental results.

An Extended Analytical Algorithm for Optimal Designing of a TORUS-type Non-slotted Axial-Flux Permanent Magnet Motor

This paper presents an analytical algorithm for optimal designing of double-sided TORUS-type non-slotted axial-flux permanent magnet motors with surface mounted magnets. For this purpose, the machine design process is treated here as a procedure that receives the machine rated parameters and design constraints and yields the optimal values of various design parameters. The design optimization problem is established here on categorizing the design parameters into several groups. The decision variables are specified as selective parameters. The constraints are imposed through the developed equations for sizing and performance prediction of the machine, yielding the calculable parameters analytically and independently from finite element analysis (FEA). The objectives are the machine efficiency and power density, which are finally maximized based on PSO algorithm. The design algorithm was implemented in MATLAB, and the solution was then employed for validation through simulating by FEA and fabricating an experimental prototype. The fabricated machine has a compact size and appropriate performances under various loading conditions. The program solution is also compatible with the results of FEA and experiment on the fabricated prototype. These all demonstrate the accuracy and efficiency of the proposed machine design algorithm.

Design and testing of a laboratory scale test rig for wave energy converters using a double‐sided permanent magnet linear generator

This study considers the design and testing of a laboratory scale test rig for wave energy converters (WECs). The main element of the test rig is a double-sided permanent magnet linear generator (PMLG). In this study, the authors describe the detailed design of the PMLG. The objective of the design is to find the detailed parameters of the PMLG to meet the targeted electromotive force (EMF) voltage with respect to the designed physical constraints. The design procedure is easy to follow and emphasises the practical aspects to construct the PMLG. A spreadsheet table was generated using the procedure to find the design parameters. Therefore, a designer can easily modify the parameters based on the physical constraints and the targeted EMF voltage. In addition to that, the authors explain the procedure to find the rating temperature for the generator. Finally, this PMLG is integrated with other components to form the test rig. The experiment is conducted to show how close the performance of the constructed PMLG is, in term of its EMF voltage and rated thermal, to the designed values. Additional tests were also conducted to test the performance of the test rig using various scenarios similar to ocean wave profiles.

Comparative study and experiment of a double-sided permanent magnet linear synchronous generator according to magnetization pattern

This paper presents a comparison of efficiency and mover mass on a double-sided permanent magnet linear synchronous generator (PMLSG) according to its magnetization pattern. When a PMLSG has a lighter mover, it has advantages such as lower cost and other aspects regarding mechanical losses. In general, PMLSGs are used with a vertical PM pattern, but we propose a horizontal PM pattern in this paper because the horizontal PM mover does not need a back-iron for the magnetic path. Electromagnetic field analysis is especially essential when analyzing the characteristics of PMLSGs. For this type of analysis, commercial finite element analysis tools are widely used because they offer convenient user interfaces that provide very accurate analytical results. Based on two-dimensional finite element analysis, we got results for two different patterns and compared them with our experimental results. Finally, the results of this analysis and the test results obtained confirm the validity of the model and the superiority of the horizontal pattern proposed in this paper.

Optimum design of a double-sided permanent magnet linear synchronous motor to minimize the detent force

In the permanent magnet linear synchronous motor (PMLSM), force ripple is harmful, useless and disturbing. The force ripple is basically composed of two components: detent force and mutual force ripple. This force is influenced by the geometric parameters of the permanent magnet (PM) motors; such as width, thickness and length of the magnet poles, length and thickness of the rotor and stator, and stator slot shape. For design optimization, the force ripple can be considered as the objective function and geometric parameters can be considered as design variables. In this paper, the distribution of magnetic flux density in the air gap is calculated using an analytical method, then detent force is computed by integrating the Maxwell stress tensor; that is expressed in terms of flux density distribution on the slot face and end face of the iron core of moving parts. The analytical result is compared with FEM simulation to verify the model. The geometric parameter effect on the detent force is investigated. Finally, using genetic algorithm, the optimum design of a linear synchronous motor with minimum detent force is obtained.

Experimental Evaluation on Power Loss of Coreless Double-side Permanent Magnet Synchronous Motor/Generator Applied to Flywheel Energy Storage System

This paper deals with the experimental evaluation on power loss of a double-side permanent magnet synchronous motor/generator (DPMSM/G) applied to a flywheel energy storage system (FESS). Power loss is one of the most important problems in the FESS, which supplies the electrical energy from the mechanical rotation energy, because the power loss decreases the efficiency of energy storage and conversion of capability FESS. In this paper, the power losses of coreless DPMSM/G are separated by the mechanical and rotor eddy current losses in each operating mode. Moreover, the rotor eddy current loss is calculated by the 3-D finite element analysis (FEA) method. The analysis result is validated by separating the power loss as electromagnetic loss and mechanical loss by a spin up/down test.

해석적 방법을 이용한 슬롯리스 양측식 코어드 타입 영구자석 발전기의 와전류 손실 해석

해석적 방법을 이용한 슬롯리스 양측식 코어드 타입 영구자석 발전기의 와전류 손실 해석

Analysis and Optimization of a Double-Sided Air-Cored Tubular Generator

Compared with the slotted tubular generators, air-cored tubular generator has no attraction force, smaller thrust ripple and lower moving mass. The advantages of high respond speed and high output stability make the air-cored tubular generators to be research focus in recent years. It is used in energy conversion systems of ambient vibrations, free-piston engine, ocean wave energy and so on. And in order to overcome the disadvantage of low power density caused by high equivalent air-gap, a tubular generator with double-sided permanent magnet (PM) arrays is proposed. The construction of the tubular generator topology is shown in Fig.1. The two sets of the corresponding Halbach PM array in the stators can help to increase the flux density in the air-gap to enhance the electromagnetic force and power density of the generator. In [1], an equivalent magnetic circuit model of the generator was established and basic characteristics were analyzed. In [2], the force characteristics of the generator with different phases were compared and the influence of the dimensions on the forces was analyzed.