Search Results (7)

The propulsion system is a critical component of medium–low-speed maglev trains and the single-sided linear induction motor (SLIM) has been adopted to generate thrust. However, the SLIM operates periodically in maglev trains. The temperature of the secondary plate of the SLIM rises significantly due to eddy currents when the train enters and leaves the station, where large slip occurs. Subsequently, the temperature decreases through natural cooling during the shift interval time. This periodic operating condition is rarely addressed in the existing literature and warrants attention, as the temperature accumulates over successive periods, potentially resulting in thermal damage and thrust variation. Furthermore, the conductivity of plate varies significantly in the process, which affects the losses and thrust, requiring a coupled analysis. To investigate the temperature variation patterns, this paper proposes a coupled model integrating the lumped parameter thermal network (LPTN) and the equivalent circuit (EC) of the SLIM. Given the unique structure of the F-shaped rail, the LPTN mesh is well designed to account for the skin effect. Three experiments and a finite element method (FEM)-based analysis were conducted to validate the proposed model. Finally, optimizations were performed with respect to different shift interval time, plate materials, and carriage numbers. The impact of temperature on thrust is also discussed. The results indicate that the minimum shift interval time and maximum carriage number are 70.7 s and 9, respectively, with thrust increasing by 22.0% and 22.0%. Furthermore, the use of copper as the plate material can reduce the maximum temperature by 22.01% while decreasing propulsion thrust by 26.1%. Full article

This article presents the impact analysis of space harmonics’ presence on a single-sided three-phase linear induction motor, along with a comprehensive parametric investigation. The presence of space harmonics often reduces the linear induction motor’s performance. The electromagnetic phenomena are governed by Maxwell’s equations. The chosen mathematical model uses a 2D formulation with magnetic vector potential. The model implementation is performed using the finite element method on the free Gmsh-GetDP platform. The electromagnetic thrust is calculated in the current excitation case using two numerical models of the finite element method with and without term-generating space harmonics in order to highlight their effect. The adaptation to voltage supply operation is obtained via equivalent electric circuits through the calculation of the operational impedance. The choice of the machine’s parameters by the designer in order to enhance its performance or reduce energy consumption is a difficult task. The analysis and the determination of the dependence of the parameters and the performance are necessary. The main objectives of this study are to determine this dependency and to analyze the space harmonic impact of the linear induction motor’s parameters on its performances. A comparative exploration of space harmonics’ presence using two numerical models (single and multiharmonics) and an assessment of the parametric effect of space harmonics’ presence on various machine characteristics such as thrust, efficiency, and power factor have been carried out. The motor’s characteristics (i.e., thrust, efficiency, and power factor) strongly depend on parameters such as the pole pair number and conductivity. Improving the operation and maximizing the performance of such a machine for a given specification requires the use of optimization algorithms. Motor characteristics (thrust, efficiency, and power factor) are highly dependent on parameters such as the number of pole pairs and conductivity. Full article

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. Full article

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. Full article

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. Full article

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. Full article

This paper presents a 2D hybrid steady-state magnetic field model, capable of accurately modeling the electromagnetic behavior in a linear induction motor, including primary slotting, finite yoke length, and longitudinal end-effects by primary motion. This model integrates a complex harmonic modeling technique with a discretized magnetic equivalent circuit model. The Fourier model is applied to regions with homogeneous material properties, e.g., air regions and the track of the motor, while the magnetic equivalent circuit (MEC) approach is used for the regions containing non-homogeneous material properties, e.g., the primary of the linear induction motor (LIM). By only meshing the domains containing highly-permeable materials, the computational effort is reduced in comparison with the finite element method (FEM). The model is applied to a double-layer single-sided LIM, and the resulting thrust and normal forces show an excellent agreement with respect to finite element analysis and measurement data. Full article