Single-sided Linear Induction Motor Research Articles

A Novel MMF Distribution Model for 3-D Analysis of Linear Induction Motor With Asymmetric Cap-Secondary for Metro

This paper develops a novel magnetomotive forces (mmfs) distribution model along the transverse direction for the 3-D analysis of linear induction motor, and it investigates the influence of a laterally asymmetric cap-secondary on the thrust, vertical force, lateral force, and efficiency in a prototype single-sided linear induction motor for linear metro. First, the mmf distribution model and its working conditions are defined, and the model is transferred into a mathematical model. Second, the air-gap flux and secondary eddy current in a prototype linear motor with a cap-secondary are obtained by a 3-D space harmonic analytical method. Third, the thrust, vertical force, lateral force, and efficiency of the test motor are analyzed with various lateral deflection, and the power factor in secondary is also presented. Finally, these results are experimentally verified by measurements on the test rig of the linear motor, and the comprehensive effect on the operating performance can be accurately calculated by the mmf model.

Investigation of Forces and Secondary Losses in Linear Induction Motor With the Solid and Laminated Back Iron Secondary for Metro

In this paper, two main kinds of the secondary, i.e., the solid and laminated back iron secondary, are applied in linear metro, as well as electromagnetic forces and secondary losses of the single-sided linear induction motor (SLIM) with different secondary are calculated by the finite-element method (FEM). First, in solving region, the fundamental equations of the magnetic field with eddy currents in the secondary are deduced, and specific boundary conditions for each part of SLIMs are given. Equations of the secondary loss and efficiency are presented. Second, 120-kW SLIMs with two types of the secondary for metro are calculated by the three-dimensional FEM, respectively. The efficiency and secondary loss are analyzed for different numbers of the lamination in the secondary back iron. The optimal number of the back iron lamination is then obtained. Third, considering the influence of the end and edge effect, the air gap flux density with different secondaries is calculated. Then, the thrust and vertical force are analyzed for SLIMs with two kinds of the secondary. Finally, numerical results of the efficiency, thrust, and vertical force, which are obtained from different secondaries, are experimentally validated by measurement on the test rig of the SLIM.

Influence of parameters of cap‐lamination secondaries on performances in single‐sided linear induction motors

The secondary is an important design factor of single-sided linear induction motors (SLIMs), as well as has influence on the cost and performance of SLIMs. In this study, the cap-lamination secondary is designed and relations of the secondary parameter and performance of SLIMs are calculated. First, the aluminium (Al) cap and lamination back iron of the cap-lamination secondary are designed and discussed. Then, improvements in performance caused by two potentially significant effects of the cap-lamination secondary, i.e. the thick cap edge and lamination, are identified. Second, a flat-solid secondary is applied and two SLIMs, which are the same primary and two different secondaries, are calculated by three-dimensional finite-element method. Eddy current densities in the Al and back iron plate, which are two parts of the secondary, are analysed. Owing to different transverse edge effects, variations of the air-gap flux density are calculated with different secondaries. Finally, the numerical results of the thrust, power factor, and efficiency are experimentally validated by measurements on test rig of SLIMs. It shows that the SLIM with cap-lamination secondary, which has higher performance, is affected greatly by the conductor structure of the secondary and the lamination of the iron back plate.

Thrust Analysis and Experiments on Low-Speed Single-Sided Linear Induction Motor

When the characteristics of a linear induction motor (LIM) are analyzed using finite element analysis (FEA), it is desirable to set the voltage source as an input. If the voltage source is set as an input in FEA, the leakage inductance and primary resistance of the equivalent circuit must be entered by direct calculation, and the magnetizing inductance and secondary reaction effects are directly considered in FEA. Exact calculation is necessary because the primary winding resistance and leakage inductance directly entered will have a significant effect on the LIM output. Therefore, in this study, we accurately calculated the primary leakage inductance and analyzed the resulting LIM characteristics. We calculated the leakage inductance using an analytical equation and FEA, and we confirmed the accuracy by comparing the results with the value experimentally calculated using a manufactured model. We also analyzed the instrument performance and thrust of the LIM as a function of the difference in the leakage inductance. Finally, we present the conclusions on the precise analysis based on the calculation of the leakage inductance.

Distribution of Static Magnetic Field Characteristics of Linear Induction Motor

In this paper, theoretical and practical design of low speed single side linear induction motor of secondary as reaction rail is proposed. At no load condition, a DC voltage is injected to the stator winding to one of the phase to analyse the static magnetic field across the mean length and also to the other phases dc voltage is injected and analysed that the magnetic flux shift spatially that makes the flux travels from one end of the primary to the other end. For increasing input dc current the magnetic flux density also increases by its square. By applying ac voltage, the output speed, thrust characteristics are measured. The static magnetic field and output characteristics of linear induction motor had analysed through experimental calculations.

Analysis of Finite Width Effects of Single-sided Linear Induction Motor Using Hankel Functions

Construction of a prototype Single Sided Linear Induction Motor (SLIM) is not possible taking stator and rotor width to be infinite because the formation of stator winding is not possible without the overhang. Also the current path in the rotor sheet cannot be made of closed type until and unless rotor width is finite. This study takes into account, the finite width effects of both stator and rotor but ignores the discontinuity of the rotor in the longitudinal direction. The finite width effects in a SLIM are analyzed using special mathematical tools such as Hankel Function for faster numerical convergence. The basic difficulty in formulating such problem, based on electromagnetic field theory applications, is to calculate the induced current in the rotor sheet, which is electrically decoupled from the stator winding system. It is also known that currents in the rotor sheet are generally computed, based on the fact that current cannot escape the sheet. Therefore, the divergence of rotor current density being zero calls for introduction of a field quantity “Stream Function”. The present paper uses stream function effectively for tackling the above said difficulty. The results presented in the study are compared with the values of a model with stator and rotor of finite width. Such comparison results can help a designer to decide a finalized value of stator and rotor width.

Force Study of Single-Sided Linear Induction Motor

In this paper, complex Poynting theorem is used to calculate the power transmitted from primary to other areas of single-sided linear induction motor. By the help of Poynting theorem and boundary conditions, the longitudinal end effect is completely included into the analysis. Having comprehensive information about power flow and using the coenergy method, it is possible to calculate traction and normal forces due to each existing wave. So, it is shown that each of the traction and normal forces consists of five components. Then, the effect of some important design parameters on the calculated components of forces is analyzed. Results by the proposed model have been compared with those evaluated by finite-element method and with experimental measurements.

Hardware-in-the-Loop Emulation of Linear Induction Motor Drive for MagLev Application

Linear induction machines are widely used in transportation systems due to their many advantages. Design and prototyping of electric machines are an expensive and time-consuming process; hardware-in-the-loop simulation provides an efficient alternative. In this paper, a field-programmable gate array-based real-time digital emulation of single-sided linear induction motor with the drive system is proposed. Implementation of the model is performed in both fixed-point using Xilinx system generator and floating-point number representations using a handwritten VHSIC Hardware Description Language code. Then, an evaluation in terms of real-time step-size and accuracy as well as hardware resource utilization is provided. The whole design was fully paralleled, which resulted in a considerable reduction of model execution time. The minimum time step of 2.3 and 0.8 $\mu \text{s}$ was achieved for floating-point and fixed-point implementations, respectively. The results of the real-time simulation are verified by the experimental results as well as a 2-D finite-element simulation in JMAG software.

Matrix converters and three-phase inverters fed linear induction motor drives—Performance compare

Abstract In this paper, the system of the Linear Induction Motor (LIM) driven by direct AC–AC matrix converter is presented and its dynamic performance is briefly compared with the conventional LIM drives based on AC–DC–AC converter. Space-vector pulse-width modulation (SVM) and indirect field oriented control (IFOC) are applied to control the two employed converters. For the sake of comparison, the PI controllers are applied to control the primary (mover) speed and current considering the same parameter settings. The objective of this paper was to compare theoretically the dynamic performance of linear induction motor (single-sided LIM) drives driven by three-phase voltage source inverters and the direct AC/AC matrix converters. The study compares the dynamic performance in addition to the harmonics content and THD of the input and output voltage and current for both converters. The simulation of each system has been implemented using the MATLAB/SIMULINK platform.

Analysis of Torques in Single-Side Linear Induction Motor With Transverse Asymmetry for Linear Metro

Due to the magnetic distortion and nonuniform force density of the single-side linear induction motor (SLIM) caused by the lateral movement, edge, and end effects, three types of torques, i.e., the side, normal, and horizontal torques, are produced. This paper investigates these special torques of the SLIM for metro and the variations of these torques when the primary is displaced sideways from a symmetrical position. It is of prime importance to take longitudinal end effects, edge effects, overhang of the primary windings, and lateral displacement into consideration when the air-gap flux density distributions and special torques are calculated via a 3-D analytical method. The air-gap flux density distributions along longitudinal and transverse directions, as well as the force density and torques with the different lateral displacements, are comprehensively investigated when the motor works in the motoring operation. The analytical results are experimentally validated by measurements on a reciprocal power-fed test rig. It shows that the horizontal and side torques, which increase the instability of the suspension system and the antirolling bar of bogie, increase almost linearly with the increase of the lateral displacement. Normal torque decreases with the increasing lateral displacement.

Analysis of forces in single‐side linear induction motor with lateral displacement for linear metro

This study investigates the influence of lateral displacement of the primary on the thrust, vertical and lateral forces in a single-side linear induction motor for linear metro. A three-dimensional analytical model, which is able to consider the longitudinal and transversal end effects, overhang of the primary windings and lateral displacement, is developed to obtain the air-gap flux density distributions along longitudinal and transverse directions as well as forces. Variations of the thrust, vertical and lateral forces with the lateral displacements are comprehensive investigated when the motor is torque motoring, negative sequence braking or regenerative braking operation. The analytically predicted results are experimentally validated by measurements on reciprocal power-fed test rig. It shows that the thrust and vertical force of single-side linear induction motor decrease almost linearly with the increase of the lateral displacement in all regions, and lateral force is restoring which helps centralising the railcar in the regenerative braking and most parts of motoring regions.

Electromagnetism calculation of single‐sided linear induction motor with transverse asymmetry using finite‐element method

Electromagnetic variations of the single-sided linear induction motor (SLIM) are calculated by three-dimensional (3D) finite-element method (FEM) when the primary is displaced sideways from a symmetrical position. For geometrical and electrical asymmetry, a full 3D model, which considering the longitudinal and transverse end effects, overhangs of the primary windings and secondary, as well as lateral displacement, is developed. Apart from the thrust and vertical force, lateral force is produced when the transverse asymmetry occurred. Hence, the calculation equation of thrust, vertical and lateral forces in each element of the 3D FEM model and boundary conditions are presented. Air-gap flux densities along the longitudinal and transverse directions with different lateral displacements are obtained, as well as the distortion coefficients of the air-gap flux density is proposed. Corresponding induced currents in the secondary are predicted. Finally, the variations of the thrust, vertical and lateral forces are experimentally validated by measurements on reciprocal power-fed test rig. It shows that the flux in between overhangs of the primary winding and secondary has great effect on the lateral force, the thrust and vertical force decrease with the increase of the lateral displacement.

Robust tracking performance of linear induction motor‐based automatic picking system using a high‐gain disturbance observer

To operate the movable ejectors of an automatic picking system (APS) with high dynamics and high precision, a robust speed tracking controller design for a single-sided linear induction motor (LIM) is presented using a high-gain disturbance observer method. The thrust disturbance as well as the mechanical parameter variation due to the mass change influences directly the tracking control performance of APS. To guarantee robustness in the presence of such uncertainty, a high-gain disturbance observer-based linear quadratic regulator (LQR) is designed from the mechanical dynamics. Since the estimated disturbance effectively cancels out real uncertainties in the system, the resulting system behaves like the closed-loop system consisting of the disturbance-free nominal model and the LQR. Since MATLAB–Simulink does not support a library for a LIM, a Simulink library model has been developed using the LIM dynamics. To verify that the proposed scheme has a robust control nature, the comparative simulations are carried out based on the library. The whole control system is implemented using DSP TMS320F28335 for a LIM driven by a three-phase voltage-fed pulse-width modulation inverter. Through comparative experimental results in the presence of disturbances, the effectiveness and robustness of the proposed scheme are verified.

Full-order Luenberger observer based on fuzzy-logic control for sensorless field-oriented control of a single-sided linear induction motor

This paper investigates sensorless indirect field oriented control (IFOC) of SLIM with full-order Luenberger observer. The dynamic equations of SLIM are first elaborated to draw full-order Luenberger observer with some simplifying assumption. The observer gain matrix is derived from conventional procedure so that observer poles are proportional to SLIM poles to ensure the stability of system for wide range of linear speed. The operation of observer is significantly impressed by adaptive scheme. A fuzzy logic control (FLC) is proposed as adaptive scheme to estimate linear speed using speed tuning signal. The parameters of FLC are tuned using an off-line method through chaotic optimization algorithm (COA). The performance of the proposed observer is verified by both numerical simulation and real-time hardware-in-the-loop (HIL) implementation. Moreover, a detailed comparative study among proposed and other speed observers is obtained under different operation conditions.

Design Optimization of a Ladder Secondary Single-Sided Linear Induction Motor for Improved Performance

In this paper, design and optimization of a ladder-type single-sided linear induction motor (Ladder SLIM) for machine tool applications is investigated. High-speed linear induction machines suffer from the end-effect phenomenon, which can reduce the thrust and result in declined output characteristics. Although it is common to consider this phenomenon in high-speed applications, it is essential to take it into account in the design and analysis of low-speed low-air-gap linear machines. In addition, Ladder SLIMs have significant flux density ripples, and using skewed bars for secondary of the machine is a common solution for it. Therefore, providing required equations, an algorithm for designing a Ladder SLIM considering the end-effect phenomenon based on Duncan model is proposed, and effect of several design parameters on the output characteristics are analyzed. In order to find the optimum design parameters, a multiobjective optimization problem considering efficiency, power factor, and braking force due to the end effect is defined. This problem is optimized with two algorithms, interior point and genetic algorithms, and results are compared. Finally, the validity of the obtained solution is verified using a 2-D and 3-D time-stepping finite-element method.

Derivation of Equivalent Circuit Parameters for Single-Sided Linear Induction Motors

A $\pi $ model of equivalent circuit has been proposed for single-sided linear induction motors, whose parameters have been obtained using the 1-D field analysis method and the complex Poynting theorem. The longitudinal end effect (LEE), transverse edge effect, saturation effect in secondary back iron, and half-filled primary slots are included in the suggested method. The LEE is considered, completely, with the help of the Poynting theorem and new boundary conditions. The well-known iterative method is modified to improve the calculation accuracy of saturation factor, $K_{s}$ , the permeability of back iron, and the equivalent secondary resistance. The effect of half-filled primary slots is also included by the modification of the effective motor length and the primary equivalent current sheet. The simulation results are evaluated by the finite-element method and experimental measurements.

Variable slip‐frequency strategy for reducing non‐equal deviations output by paralleled single‐sided linear induction motors

A predictive variable slip-frequency (PVSF) control strategy is presented to reduce non-equal output thrust deviation even though the existence of primary imbalancing input current is allowed. Besides current and speed sensors, the proposed strategy takes no additional sensors for that it only employs the real-time speed signal and the latest instantaneous slip-frequency to generate the predictive dynamical slip-frequency corresponding to deviation of thrust output by paralleled single-sided linear induction motors (SLIMs) groups. Owing to its insensitive to primary current d/q axes components for the generation of variant slip-frequency, the PVSF strategy owns a significant anti-noise ability since as big inertia system, the speed of parallel SLIM groups cannot vary abruptly. Both simulations and experimental results verify the feasibility of the proposed PVSF strategy.

Sensorless Indirect Field Oriented Control of Single-sided Linear Induction Motor With a Novel Sliding Mode MRAS Speed Estimator

This paper proposes a new sliding mode control (SMC) based model reference adaptive system (MRAS) for sensorless indirect field oriented control (IFOC) of a single-sided linear induction motor (SLIM). The operation of MRAS speed estimators dramatically depends on adaptation mechanism. Fixed-gain PI controller is conventionally used for this purpose which may fail to estimate the speed correctly in different condition such as variation in the machine parameters. In this paper, PI controller is replaced by SMC based adaptation mechanism. One of the major problems of SMC is high-frequency chattering due to switching control function. In order to alleviate this problem, a new switching control function is presented. The SMC parameters are tuned using an off-line method through chaotic optimization algorithm (COA) because no design criterion is given to provide these values. The operation of sliding mode MRAS speed estimators (SM-MRAS) is validated by numerical simulation. The simulation results confirm the efficiency of proposed adaptation mechanism.

Adaptive current compensation with nonlinear disturbance observer for single-sided linear induction motor considering dynamic eddy-effect

An adaptive current compensation control for a single-sided linear induction motor (SLIM) with nonlinear disturbance observer was developed. First, to maintain t-axis secondary component flux constant with consideration of the specially dynamic eddy-effect (DEE) of the SLIM, a instantaneously tracing compensation of m-axis current component was analyzed. Second, adaptive current compensation based on Taylor-discretization algorithm was proposed. Third, an effective kind of nonlinear disturbance observer (NDOB) was employed to estimate and compensate the undesired load vibrations, then the robustness of the control system could be guaranteed. Experimental verification of the feasibility of the proposed method for an SLIM control system was performed, and it showed that the proposed adaptive compensation scheme with NDOB could significantly promote speed dynamical response and minimize speed ripple under the conditions of external load coupled vibrations and unavoidable feedback control variables measured errors, i.e., current and speed.

A New Approach to Evaluate Influence of Transverse Edge Effect of a Single-Sided HTS Linear Induction Motor Used for Linear Metro

A new approach has been proposed to evaluate the influence of the transverse edge effect of high-temperature superconducting (HTS) linear induction motor (LIM) in this paper. Taking a 3.5 kW single-sided HTS LIM for an example, the cross-flux density distributions were analyzed by analytical method. Based on results mentioned above, a new transverse coefficient was proposed to evaluate the influence of the transverse edge effect on the cross-flux density distribution. The influences of the motor configurations and parameters on the transverse coefficient were also investigated. The 3-D finite-element method was adopted to verify the accuracy of the presented analytical method.