Single-sided Linear Induction Motor Research Articles

Decoupling control of three-dimensional electromagnetic forces in linear induction motors based on novel equivalent circuit

Since the single-sided linear induction motor not only produces thrust, but also produces vertical and transversal forces, if no specific control is applied, vertical and transversal forces can have a negative effect on the load propelled by the motor, especially in the application of the railway transit. Therefore, the best solution to the above issues is to independently control the vertical force or transversal force without changing the thrust in the motor. First, this paper presents a 3-D electromagnetic forces, i.e. thrust, vertical and transversal forces, decoupling strategy for the single-sided linear induction motor based on a novel equivalent circuit considering the longitudinal end effect and 3-D electromagnetic forces. Then, the slip-frequency calculator, thrust observer and thrust controller in the conventional vector control for induction motors are reconstructed, and a force decoupling controller is proposed. Finally, the simulation to verify the vector control with the force decoupling controller for the linear motor is performed by using a prototype motor which is used for railway transit.

Normal Force Elimination in Single-Sided Linear Induction Motor Using Design Parameters

In this article, the normal force acting on the primary of single-sided linear induction motors (SLIMs) is analytically derived. Considering all phenomena involved, the effects of different design variables on the normal force are investigated. In some applications such as transportation systems, the normal force elimination may be required or strongly beneficial, and, in this article, a multi-objective design optimization method based on genetic algorithm is introduced for this purpose, both with and without consideration of primary weight effect. All significant design variables are considered in the optimization. The results show that the motor performance is improved and the normal force is eliminated by an appropriate selection of design variables. To evaluate optimization effectiveness, a laboratory prototype has been constructed, tested, and numerically simulated by finite element analysis (FEA). Comparing the experimental and FEA results with analytical predictions confirms the accuracy and usefulness of the proposed design methodology.

A Novel Analytical Equivalent Circuit for Single-Sided Linear Induction Motors Considering Secondary Leakage Reactance

Single-sided linear induction motors usually appear in magnetic levitation systems of transportation. Since the beginning of such developments, edge effects represent one of the great challenges to overcome in analytical modelling. For almost four decades, in order to simplify the mathematical treatment of border effects, most analytical models have not considered the secondary leakage flux properly. Although concise and accurate in most cases, such approaches have deficiencies in slotted secondaries. This paper presents an analytical equivalent circuit that considers the secondary reactance for both edge effects, i.e., entry and exit sides. The proposed approach uses an analogical RLC circuit which describes the behavior of magnetizing (exit) and demagnetizing (entry) waves, as well as adapted correction factors for transverse effects. By means of an 8 pole/120–175 N prototype, the measured thrust and vertical forces remarkably validate the model for frequencies equal or higher than 60 Hz. The relevance of secondary reactance in such cases can be explained by accounting its influence, specially, in the rise of the demagnetizing entry wave.

Performance Comparison of Slim Drive with ANFIS Controller

Normally speed control of a Single-Sided Linear Induction Motor (SLIM) by an indirect vector control scheme is difficult because the motor's parameters are time-dependent and the performance depends on various factors such as end effect, saturation, location of primary losses, and iron losses. Traditional PI current regulators are commonly used in vector regulators, but there is a tuning problem due to the oscillation of an operating point. This problem can be overcome by substituting an adaptive neuro-fuzzy-based current controller, and this controller improves the operation of a SLIM, such as its motor speed and thrust force. In this adaptive neuro-fuzzy controller, the ID and IQ errors and the error delay are inputs, and its outputs are Vds and Vqs, respectively. It is trained based on available values. A SLIM's dynamic modelling is implemented by dividing current (I) and flux-linkages into two terms. In these two terms, one is dependent on the end effect, and the other is independent of the end effect. The function of a Voltage Source Inverter (VSI)-fed indirect vector-controlled SLIM drive is simulated in MATLAB/Simulink, and its operation under various operating conditions is studied using an adaptive neuro-fuzzy current controller. These results are compared to a traditional P-I controller. The Pulse Width Modulation (PWM) technology that is used for controlling the VSI is called Space Vector Modulation (SVM).

Design Aspects and Thermal Characteristics of Single-Sided Linear Induction Motor for Electromagnetic Launch Application

This paper presents the design aspects and thermal characteristics of single-sided linear induction motor (SLIM) for Electromagnetic launchers. It is designed to accelerate a 50 kg mass through a distance of 3 meters within a minuscule time to an exit velocity of 50 m/s. A study of the motor’s parametric variation based on the launching requirement has been performed. Its performance characteristics are obtained using 3D FEM and verified analytically using Parseval’s method. The FEM, analytical and experimental verification of the thrust characteristics of different secondary conductive sheet materials namely, aluminum, beryllium copper and German silver shows that, the latter exhibits superior characteristics than the former two, because its thrust-velocity curve is close to inverse linear relationship (stable region of operation of LIM), which significantly reduces the accelerating time during the launch. The designed SLIM is assessed for its thermal performance with materials having temperature-dependent electrical properties by carrying out a coupled-field FEM simulation. The conclusions demonstrate that the electromagnetic and thermal assessments are in tandem with each other as required for launching.

Analysis of Coupled Thermal and Electromagnetic Processes in Linear Induction Motors Based on a Three-Dimensional Thermal Model

The article describes a mathematical model of interconnected electromechanical and thermal processes in a linear induction motor (LIM). Here, we present the structure of the thermal model and provide the calculation formulas of the model. The thermal model consisted of eight control volumes on each tooth pitch of the LIM. Moreover, we also present a model of electromechanical processes and its interaction with the thermal model. The electromechanical model was based on the detailed magnetic and electrical equivalent circuits of the LIM. Model verification was performed using a model based on the finite element method and using experimental data. We also conducted a study focused on the necessity of considering the influence of various features of the thermal processes. We herein discuss the application of the model implemented in the MATLAB/Simulink, which was used to analyze the thermal performance of linear transport and technological induction motors. For the traction single-sided linear induction motor, we determined limits of safe operation by considering the unevenness of heating along the length in two cases: natural cooling and forced cooling. For forced cooling, required values of air flow were determined. For the arc induction motor of the screw press, the influence of various factors (i.e., reduction of the stroke, the use of a soft start, and the use of a forced cooling) on heating was evaluated.

Design Optimization of Secondary Element of Single-Sided Linear Induction Motors Using a Genetic Algorithm

The article focuses on the use of genetic algorithms for the design of linear induction motors. Comparison of genetic algorithm with classical methods in the context of electrical machines designing has been carried out. The results of solving an optimization problem for two designs are presented, viz. a laboratory linear induction electric motor based on a three-phase SL-5-100 inductor and a traction single-sided linear induction electric motor of an urban transport system. The optimality criterion included maximizing the power factor and efficiency, as well as the rigidity of the mechanical characteristic while ensuring a starting traction force of at least a set value. The results of optimization of such parameters of the secondary element as the width and thickness of the conductive strip as well as the thickness of the magnetic circuit are described. The relevance of the problem of optimizing the parameters of the secondary element with unchanged parameters of the inductor is due to the fact that the same inductor can be used to build various structures, while the secondary element is created for each specific application and integrated directly into the working body of the mechanism or is a driven product. To calculate the traction and energy characteristics of linear induction electric motors, an electromagnetic model based on detailed equivalent circuits was used, taking into account longitudinal and transverse edge effects and providing a calculation time for one set of parameters of about 1 s. In accordance with this model, the electric motor is reduced to a set of three detailed equivalent circuits: a magnetic circuit, primary and secondary electrical circuits. The result of the optimization of these electric motors was an increase in the efficiency by 1.6 and 1.4 %, respectively, an increase in the power factor by 0.9 and 0.2 %, and an increase in the rigidity of traction characteristics and starting traction force.

Corrigendum: Dynamic air gap asymmetry fault detection in single‐sided linear induction motors

IET Electric Power ApplicationsVolume 16, Issue 1 p. 137-137 CORRIGENDUMOpen Access Corrigendum: Dynamic air gap asymmetry fault detection in single-sided linear induction motors This article corrects the following: Dynamic air gap asymmetry fault detection in single-sided linear induction motors Jawad Faiz, Mehrage Ghods, Armin Tajdyni, Volume 14Issue 4IET Electric Power Applications pages: 605-613 First Published online: February 25, 2020 First published: 26 September 2021 https://doi.org/10.1049/elp2.12138AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In [1], the following corrections should be noted. The spelling in the author name Arman Tajdiny is updated and the ORCID is included. Arman Tajdiny https://orcid.org/0000-0001-8333-6391 REFERENCE 1Faiz, J., Mehrage, G., Tajdiny, A.: Dynamic air gap asymmetry fault detection in single-sided linear induction motors. IET Electr. Power Appl. 14(4), 605– 613 (2020). https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/iet-epa.2019.0323Wiley Online LibraryWeb of Science®Google Scholar Volume16, Issue1January 2022Pages 137-137 ReferencesRelatedInformation

Design and Force Analysis of Salient Single-Sided Linear Induction Motor

The linear induction motors, due to their unique features, utilize in various applications. The most crucial drawback of the linear induction motors is the large air gap between secondary and primary. This problem deteriorates the performance of linear induction motor, increases power loss, and causes to low efficiency. In this paper, a novel structure of single-sided linear induction motor is proposed to reduce the magnetic air gap. This structure consists of ladder-slit sheets and salient back iron for secondary of single-sided linear induction motor. The salient parts of back iron fill the slits of sheet, and therefore, the effective magnetic air gap can be decreased owing to partial form. Also, the electromagnetic aspects of the proposed secondary such as z-component of air gap flux density, y-component of aluminum eddy current density, and three components of Lorentz force are analyzed. Also, the finite element method and the analytical method is used for the 3 D analysis of the edge effects as well as the end effects. To show the advantages of the proposed structure, the results are compared with other secondary structures. The results show that the thrust and efficiency of the salient single-sided linear induction motor increased in comparison with other ones.

Modeling for the Electromagnetic Dynamic Distortion Effect of the Induction-Based Electrodynamic Suspension Reaction Spheres

The electrodynamic suspension reaction sphere (EDSRS) is regarded as a novel actuator for the spacecraft attitude control system. The omnidirectional rotation of the EDSRS spherical rotor brings about the dynamic distortion of the electromagnetic force and torque characteristics. With the mechanical structure of the EDSRS simplified and equivalent to multi-degrees of freedom (DOF) single-sided linear induction motor (LIM), this article first proposes a 3-D LIM analytical electromagnetic force model by employing the electromagnetic physical quantities in the 2-D Fourier series expansion form. Then, an analytical electromagnetic force and torque model considering the electromagnetic dynamic distortion effect (EDDE) of the EDSRS is established based on the previous LIM force model according to the motion decomposition principle. Finally, the proposed analytical EDDE model is experimentally validated on the developed laboratory prototype.

Longitudinal Dynamic End Effect of Single-Sided Linear Induction Motor for Medium–Low Speed Maglev

Longitudinal Dynamic End Effect of Single-Sided Linear Induction Motor for Medium–Low Speed Maglev

A Modified Dynamic Model of Single-Sided Linear Induction Motors Considering Longitudinal and Transversal Effects

This paper proposes a modified dynamic equivalent circuit model for a linear induction motor considering both longitudinal end effect and transverse edge effect. The dynamic end effect (speed-dependent end effect) is based on conventional Duncan’s approach. The transverse edge effect is investigated by using three correction factors applied to the secondary resistance and magnetizing inductance. Moreover, the iron saturation effect, the skin effect, and the air-gap leakage effect are incorporated into the proposed model by using the field-analysis method. A new topology of the steady-state and space-vector model of linear induction, regarding all mentioned phenomena, is presented. The parameters of this model are calculated using both field analysis and the finite-element method. The steady-state performance of the model is first validated using the finite-element method. Additionally, the dynamic performance of the proposed model is studied. The results prove that the proposed equivalent circuit model can precisely predict the dynamic and steady-state performances of the linear induction.

Quasi-3D Analytic Method of the Single-Sided Linear Induction Motor With the Ladder Secondary

A quasi-three-dimensional (3-D) analytic method is presented for calculating the performance of single-sided linear induction motor with the ladder secondary. To simplify the analytic model, the ladder aluminum plate is equivalent to the flat-solid one, and the equivalent conductivity is derived and given. In the direction of the motion, the finite primary length and end effect are considered by the method of the Fourier transform and Residue theorem. In the transverse direction, considering finite width of the primary core and the region between the overhang of the primary windings and the secondary, the equivalent integral length is given. Finally, the thrust, vertical force and secondary efficiency are calculated and compared with the results of the 3-D finite-element method and experiment, it is shown that the method presented in the paper is much simpler and the accuracy of the analytic method is verified.

A New Approach for Non-Linear Time-Harmonic FEM-Based Analysis of Single-Sided Linear Induction Motor Incorporated With a New Accurate Method of Force Calculation

There are some special phenomena like longitudinal end effect, saturation effect, skin effect, edge effect, and half-filled slots which make the single-sided linear induction motor (SSLIM) analysis more complicated compared to its rotary counterparts. Finite element method (FEM) can be the best choice for complete modeling of SSLIM considering all phenomena. But it is not possible to include the non-linear magnetization curve of iron into the time-harmonic FEM analysis. Thus, this article proposes a 2-D time-harmonic FEM considering all phenomena as well as the non-linear magnetization characteristics of iron using appropriate approximation. In order to overcome the Lorentz method calculation error of vertical force caused by inherent discontinuity of magnetic field intensity at the boundaries of elements, a combined Lorentz-Maxwell method is presented. Validity of the methods and final results is proved by comparing the results with analytical results and experimental measurements.

Temperature calculation for linear induction motor in transport application with multiphysics approach

The article describes the implementation of the mathematical model of the interrelated electromechanical and thermal processes in a linear induction motor using simulation software MATLAB-Simulink. The developed model consists of electromechanical model, thermal model and cooling system (hydraulic) model which all affect each other. Temperature calculations of the traction single-sided linear induction motor for urban transportation system are performed for different regimes. The calculation results using the developed thermal model based on the thermal detailed equivalent circuit demonstrate a close concurrence with the finite element model, temperature values differ less than in 3.8-4.8%. Safe operation range for a traction linear induction motor was determined taking into account the uneven longitudinal heating using different variants of cooling systems and coolant flow values. Recommendations on their selection were formulated. Based on the calculations and following experimental testing it was determined that operation with the maximum load with current of 270 A and load force of 8,000 N is possible with the cooling air flow rate of at least 2.2 m3/s.

A 3-D Simulation of a Single-Sided Linear Induction Motor with Transverse and Longitudinal Magnetic Flux

This paper presents a novel and improved configuration of a single-sided linear induction motor. The geometry of the motor has been modified to be able to operate with a mixed magnetic flux configuration and with a new configuration of paths for the eddy currents induced inside the aluminum plate. To this end, two slots of dielectric have been introduced into the aluminum layer of the moving part with a dimension of 1 mm, an iron yoke into the primary part, and lastly, the width of the transversal slots has been optimized. Specifically, in the enhanced motor, there are two magnetic fluxes inside the motor that circulate across two different planes: a longitudinal magnetic flux which goes along the direction of the movement and a transversal magnetic flux which is closed through a perpendicular plane with respect to that direction. With this new configuration, the motor achieves a great increment of the thrust force without increasing the electrical supply. In addition, the proposed model creates a new spatial configuration of the eddy currents and an improvement of the main magnetic circuit. These novelties are relevant because they represent a great improvement in the efficiency of the linear induction motor for low velocities at a very low cost. All simulations have been made with the finite elements method—3D, both in standstill conditions and in motion in order to obtain the characteristic curves of the main forces developed by the linear induction motor.

Force performance of single-sided linear induction motors with dual-branch phase winding in low-speed Maglev train

The low-speed Maglev train adopts single-sided linear induction motors (SLIMs) as traction part. Although the phase winding normally adopts single-branch in order to avoid circulating current caused by longitudinal end effect, the influence of circul

Investigation of the key secondary parameter effecting on transverse force in the single‐sided linear induction motor

This study mainly investigates the key secondary parameter effecting on transverse force and the changing trend of its components, which include the repulsive and restoring components. Firstly, considering the transverse displacements, skin effect and end effects, the full 3D finite element models of the single-sided linear induction motor (SLIM) are built. Secondly, when the width of the secondary varies, the transverse force and its two components are presented and analysed. At the same time, the air-gap flux densities and the eddy currents along the transverse directions are calculated. Then when the topological transform of aluminium plate (e.g. Al-cap type) and back-iron plate (e.g. laminated type) are applied, the transverse force and its components are given. Finally, the transverse force, thrust and efficiencies are compared in the SLIMs with different secondaries as well as some experiments are given. It is shown that the width of the secondary is the main factor influencing the transverse force.

Dynamic air gap asymmetry fault detection in single‐sided linear induction motors

Single-sided linear induction motors (SLIMs) are used in maglev levitation systems for propelling purpose. The reasons for such usages are their capability in direct drive applications with very good dynamic performance, high reliability and high flexibility in trajectory generation. High-performance requirements of the machine demand a high saliency ratio resulting in small air gap length along the direct axis. Therefore, the air gap symmetry in the primary side and consequently the air gap asymmetry fault diagnosis is essential for the system maintenance. In this study, the air gap asymmetry fault in a SLIM is diagnosed. Since the precise definition of the air gap asymmetry fault and fault severity has not been so far introduced in the relevant literature, they are given here. The proposed fault index is the amplitude of the sideband components of the current with a particular frequency pattern. First, mathematical analysis of magnetic field is proposed, then, fast Fourier transform is applied to the current waveform in the SLIM. The spectrum of the SLIM current in the healthy and faulty cases under different loads is obtained. Time-stepping finite element method is applied to simulate the healthy and faulty motor. Experimental results are verified by the introduced theoretical index.

Design Optimization and Performance Investigation of Novel Linear Induction Motors With Two Kinds of Secondaries

In order to reduce the transverse edge effect of a single-sided linear induction motors (SLIMs) for a low-speed Maglev train, this article proposes novel SLIMs with symmetry/asymmetry double-slit secondary. First, the end effects of the conventional SLIMs with flat-solid and cap-solid secondaries are investigated based on three-dimensional (3-D) finite-element model. For the latter one, the influences of slip frequency and secondary structure parameters are obtained as well. Second, the structures of the proposed double-slit secondaries are introduced, and the topology parameters are investigated by a single-variable optimization method. Third, the force performances of SLIMs with proposed two kinds of double-slit secondaries are compared with those of the SLIMs with the traditional cap-solid secondary. Finally, a prototype of SLIM with asymmetry double-slit secondary is manufactured and tested to validate the predictions. The results show that the SLIM with the proposed asymmetry double-slit secondary can improve the force performances due to reduction in the transverse end effect.