Double-sided Linear Induction Motor Research Articles

Design and Research on the Variable Polar Distance of the Double-Sided Linear Induction Motor for Electromagnetic Catapult

According to the special technical requirements of carrier-based aircraft catapults, this paper describes the design of a variable pole distance bilateral linear induction motor. When the traditional constant pole motor is used as the catapult of carrier-based aircraft, the current frequency continues to increase during the catapult process, which greatly aggravates the burden of the motor. Therefore, we propose a variable pole length primary double-sided linear induction motor structure. Compared with the traditional constant pole motor structure, this structure can gradually increase the pole distance with an increase in speed when the current frequency remains unchanged. In contrast, the variable pole distance method with a current frequency of 200 Hz has a pole distance of 0.262 m when the displacement is 10 m, and the pole distance increases to 0.352 m when the displacement is 100 m. By maintaining a constant current frequency, this method effectively reduces the control complexity at high speed. Through the theoretical analysis and research calculation conducted on the designed motor, a finite element simulation model was also established by ANSYS 14.0, and the influence of the change in the pole distance on the performance of the motor was analyzed. The magnetic field line and magnetic density distribution of the motor are simulated and analyzed, and the validity of the theoretical calculation is verified.

A Thrust Ripple Suppression Method for Long-Primary Double-Sided Linear Induction Motors Based on Harmonic Current Injection

For the long-primary double-sided linear induction motor (LP-DSLIM) excited by the symmetrical current, there are double slip frequency ripple in the thrust due to the dynamic longitudinal end effect. The expression of thrust ripple fluctuation caused by the dynamic longitudinal end effect are deduced firstly. Secondly, the method of suppressing the injected harmonic current is adopted, the expression of each part of thrust after injection are deduced and its characteristics are analyzed, from which the feasibility of this method to reduce the thrust ripple is illustrated. Finally, finite element simulation and experiment results indicate that the thrust ripple is significantly reduced after the injection of the harmonic current.

Modeling and Cooperative Control of Segmented Long Primary Double-Sided Linear Induction Motor

In this article, a novel unit motor mathematical model (UMMM) of segmented long primary double-sided linear induction motor (LP-DSLIM) is established and a cooperative control strategy for segmented LP-DSLIM fed by one inverter is proposed. First, the conventional UMMM is theoretically analyzed. Then, a virtual secondary is introduced aiming at accurately describing the secondary current when secondary passes through the primary segments. To acquire the secondary and primary flux linkage with different coupling lengths, the secondary resistance, secondary inductance, and mutual inductance are modified by using the coupling factor. According to the established UMMM, a cooperative control strategy for segmented LP-DSLIM fed by one inverter is developed. It is that the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis of the synchronous dq coordinate system is oriented to the total secondary flux linkage, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis components of the weighted primary current control the total secondary flux linkage and thrust. The effectiveness of the proposed UMMM and cooperative control strategy is validated by simulation and experiment.

Design Optimization and Construction of Double-Sided Linear Induction Motor

Design Optimization and Construction of Double-Sided Linear Induction Motor

Optimal design of a short primary double‐sided linear induction motor based on derived Quasi‐3D equivalent circuit model using an improved differential evolution

Due to its simple construction, the linear induction motor (LIM) provides a linear driving force without any intermediate motion translation system. LIMs are widely used in various industrial applications, including maglev rail transit and the national defense industry. However, LIMs are affected by the end effect and suffer from problems such as low efficiencies and low power factors. To make improvements, in this paper, an ensemble multi-objective optimal design method for a short primary double-sided linear induction motor (SP-DLIM) is proposed. First, a simplified Quasi-3D equivalent circuit model (ECM) for an SP-DLIM applicable to the model in this paper is derived. The 3-D transient finite element method and an experimental prototype are utilised to prove that the derived ECM is accurate enough to solve the SP-DLIM optimisation problem. Second, an ensemble multi-objective optimal design method of SP-DLIM is presented, with proposed design constraints and four different optimisation problems. Then, an improved differential evolutionary (IDE) algorithm is proposed to optimise the efficiency, power factor, and tooth weight of the motor. The three-dimensional time-stepping finite element method is utilised to verify the validity of the optimisation method. Further, a comparison of the results suggests that the IDE yields the best performance to those of other advanced heuristic algorithms.

Modeling and Optimal Design of a Short Primary Double-Sided Linear Induction Motor Considering Both Transverse and Longitudinal End Effects Using Improved Differential Evolution

Modeling and Optimal Design of a Short Primary Double-Sided Linear Induction Motor Considering Both Transverse and Longitudinal End Effects Using Improved Differential Evolution

Combined Propulsion and Levitation Control for Maglev/Hyperloop Systems Utilizing Asymmetric Double-Sided Linear Induction Motors

This article presents a new method for combined levitation and propulsion control in maglev/Hyperloop systems by selectively applying AC and DC modes of operation to a group of asymmetric double-sided linear induction motors (ADSLIMs). Although adjusting the AC current magnitude of lower and upper primary windings in ADSLIMs allows simultaneous control of thrust and lift forces, the limitation of this current balancing technique prohibits them from producing a high lift force while operating with low thrust force. To overcome this limitation and to simultaneously control the thrust and lift forces of the ADSLIMs with high efficiency under different operating conditions, a combination of AC and DC modes of operation is proposed. AC mode of operation consists of feeding different AC current amplitudes to the upper and lower ADSLIM primary windings to produce and control the required thrust and lift forces. The DC mode of operation consists of controlling one or several ADSLIMs to operate with DC excitation to realize the desired lift force at lower thrusts which otherwise cannot be achieved by operating in AC mode alone. The concept of the new combined control strategy is studied using two-dimensional finite element (FE) electromagnetic simulations and compared with an Inductrack permanent magnet (PM) based passive magnetic levitation system.

Optimal Design of a Short Primary Double-Sided Linear Induction Motor for Urban Rail Transit

Linear induction motors (LIMs) have been widely used in rail transit. However, Due to the breaking of the primary core and the large air gap, the efficiency and power factor of LIMs are seriously damaged, causing a large amount of energy waste. To improve the efficiency and power factor of LIMs for urban rail transit, we present a new optimization method for the design of a short primary double-sided linear induction motor (SP-DLIM) with a rated speed of 45 km/h and small thrust. The method is based on a steady state equivalent circuit model and the differential evolutionary algorithm (DEA). Moreover, the design constraints and the objective functions are proposed for the optimization problem. Finally, the optimized SP-DLIM is simulated by 2D transient finite element method (FEM). The 2-D transient FEM results verify the accuracy of the optimization method proposed in this paper.

Comparative Study on Improved and Traditional Equivalent Circuit of Long Primary Double-Sided Linear Induction Motor

Based on the quasi-two-dimensional (2D) field model of long primary double-sided linear induction motor (LPDLIM), an improved equivalent circuit model is proposed. First, the traditional equivalent circuit of LPDLIM is reviewed. Second, the skin effect correction coefficients for the secondary equivalent resistance and excitation reactance, and the secondary leakage inductance are derived. Moreover, an improved equivalent circuit model for LPDLIMs is presented, in which the leakage reactance of the secondary is considered, and the excitation reactance and secondary resistance are modified by the correction coefficients independently. Then, the slip frequency characteristics of various effect forces and variations of forces under different operations and mechanical air gap width are presented. Finally, the calculated forces by the proposed equivalent circuit are validated by the finite element method results and also compared with that of the traditional equivalent circuit model.

Models and Methods of Designing Linear Electric Motors for Non-Ferrous Metals Industry Applications

Through substitution of rotating induction motor drives with linear ones, one can enhance the reliability and decrease the materials capacity of electrical equipment utilized by the non-ferrous metals industry. At the same time, each particular case requires a feasibility study to justify the application of the linear induction motor. Such feasibility study is based on the key technical data of the unit obtained through mathematical modelling. The authors carried out an analysis of the existing linear induction motor models. The aim of this research is to develop a number of analytical design models. This paper looks at flat double-sided linear induction motors with a short and long secondary element. Possible applications are described for such linear induction motors in the non-ferrous metals industry. A design approach and a mathematical model were developed to calculate the magnetic vector potential and the pull force of the linear induction motor with a long secondary element. An accurate solution for the magnetic vector potential was found through Fourier transformation, which, together with the expression for the pull force, provides a design model of the motor. The model parameters were chosen based on the desired mechanical performance of the motor. A linear induction motor with a long secondary element was designed for the force of 1,000 N and the speed of 2&ndash;3 m/sec. The paper describes the modelling results, as well as the technical data of the motor. Alternative design models of the motor were compared. The authors describe a design approach and a mathematical model for calculating the magnetic vector potential and the pull force of the linear induction motor with a short secondary element. The Bubnov-Galerkin method was used to find an approximate solution for the magnetic vector potential. On the basis of that solution, a linear induction motor with a short secondary element was designed for the force of 528 N and the speed of 2&ndash;3 m/sec. This paper describes some economic aspects related to the adoption of linear induction motors. It is pointed out that the low probability of failure characteristic of linear induction motors helps lower the losses related to the emergency shutdowns and unscheduled maintenance. It is also associated with lower redundancy costs.This research was funded by the Russian Foundation for Basic Research in the&nbsp;framework of the Research Project No. 20-01-00283.

A Novel, Improved Equivalent Circuit Model for Double-Sided Linear Induction Motor

A novel, improved equivalent circuit model of double-sided linear induction motors (DLIMs) is proposed, which takes the skin effect and the nonzero leakage reactance of the secondary, longitudinal, and transverse end effects into consideration. Firstly, the traditional equivalent circuit with longitudinal and transverse end effects are briefly reviewed. Additionally, the correction coefficients for longitudinal and transverse end effects derived by one-dimensional analysis models are given. Secondly, correction factors for skin effect, which reflects the inhomogeneous air gap magnetic field vertically, and the secondary leakage reactance are derived by the quasi-two-dimensional analysis model. Then, the proposed equivalent circuit is presented, and the excitation reactance and secondary resistance are modified by the correction coefficients derived from the three analytical models. Finally, a three-dimensional (3D) finite element model is used to verify the proposed equivalent circuit model under varying air gap width and frequency, and the results are also compared with that of the traditional equivalent circuit models. The calculated thrust characteristics by the proposed equivalent circuit and 3D finite element model are experimentally validated under a constant voltage–frequency drive.

Calculation of Electromagnetic Thrust for Long Primary Double Sided Linear Induction Motors with Secondary of Arbitrary Length

The expressions of the air gap flux density and secondary current density of long primary double-sided linear induction motor (LPDLIM) with arbitrary secondary length are derived by the numerical method, which with the secondary as the moving reference frame. The effects of the forward and backward components of end effects on the normal travelling wave and the secondary current density are analyzed respectively, and their temporal and spatial distributions are presented. And then the electromagnetic thrust and its ripple expression considering the longitudinal end effect of the air gap magnetic field and the components of the secondary current density are solved. The slip characteristics distribution of each electromagnetic thrust and thrust ripple components, and the contribution of end effect to resultant thrust and force ripple of the motor with arbitrary secondary length are investigated. Finally, the thrust characteristics of the LPDLIM with arbitrary length secondary are verified by the results of the FEM model. The calculation shows that the appropriate secondary length can reduce the thrust ripple of the LPDLIM.

Interpolation algorithm in designing of feed-forward robust precision control motion

Based on the structure and dynamic process of the ladder secondary double-sided linear induction motor (DSLIM) with asymmetry position of primary part of motor, the motor parameters may change with the secondary position, which directly cause the stability of electromagnetic thrust. It is difficult to meet the system control performances for designing of controller in the dynamic characteristics of the speed closed loop. This paper describes some solving algorithm by adopting the rotor field oriented control as the model matching strategy to achieve the smooth control of the electromagnetic thrust. The arrangement of model matching process is based on the Nevallina pick solution as linear interpolation method. Through the robust control concept and model matching control, the stability of the electromagnetic thrust during the motor step change process can be achieved. The simulation results verify the truth of the presented control strategies.

A study on the design of propulsion/levitation/guidance integrated DSLIM with non-symmetric structure

Research on the magnetic levitation driving system of Hyperloop which has emerged as the next new vehicle is being carried out. Recently, magnetic levitation driving systems use EMS (Electro-Magnetic Suspension) and EDS (Electro-Dynamic Suspension) methods, and both EMS and EDS methods use two or more systems for propulsion/levitation/guidance. However, using two or more driving systems cause complexity of structure of whole system and increase significantly maintenance costs. Therefore, to solve these problems, this study proposed the concept and structure of Double-Sided Linear Induction Motor (DSLIM) that can be generating propulsion/levitation/guidance in one system, and carried out basic design and performance analysis by analyzing the design requirements of DSLIM. In addition, a detailed design through the selection of design parameters and analysis of characteristics that significantly affect the output characteristics was carried out to derive a performance improvement model for DSLIM.

Modified Loop Shaping Algorithm in Designing 2-DOF Controller of a Ladder-Secondary Double-Sided Linear Induction Motors

Modified Loop Shaping Algorithm in Designing 2-DOF Controller of a Ladder-Secondary Double-Sided Linear Induction Motors

Research and Analysis of Electromagnetic Thrust of Variable Pole Distance Linear Induction Motor

According to the actual acceleration index requirements, a high-speed large-thrust linear induction motor for accelerating the system was designed. Due to the variable pole pitch design, the variation of the pole pitch plays a key role in the design, and the influence of the variation of the pole pitch on the output of the electromagnetic thrust is analyzed. The variable pole distance double-sided linear induction motor is used as the acceleration drive. It does not need to detect the speed and displacement. The primary winding current frequency is constant. As the speed increases, it will not be limited by the inverter frequency, and will not increase the motor loss. The frequency is constant and the control is optimized and simpler.

Design and Performance Investigation of the Double-Sided Linear Induction Motor With a Ladder-Slot Secondary

This paper proposes an analytical model to design and investigates the double-sided linear induction machine with a ladder-slot arrangement employed on the secondary mover. Emphasizing the longitudinal end effect, the equivalent circuits are based on Duncan's model modified by electromagnetic field analysis. By defining the ratio of ladder width to slot width (the ladder–slot ratio) equivalent circuit parameters, including the magnetizing inductance and resistance, and the secondary resistance, are estimated using formulae linked to the dimensions and geometry of the primary and secondary. The analytical model is proven to be effective through measurements made on an experimental machine. Magnetizing inductance and resistance estimates are shown to be predicted accurately using the analytical method, and the analytical method is further simplified for rapid and efficient practical design. The major contribution of this research is a practical method to optimize the design of large-scale drives using linear induction motors with a ladder–slot arrangement.

Thrust Control of a Double-Sided Linear Induction Motor With Segmented Power Supply

Due to the dynamic longitudinal end effect, the motor flux is lagging and the thrust is fluctuated in a long-primary double-sided linear induction motor (DSLIM). In this paper, a thrust fluctuation reduction method is proposed for the DSLIM with segmented power supply. The mathematical model of the DSLIM module considering the dynamic longitudinal end effect is established first, and a new field orientation is presented by solving variation of the motor flux when the secondary enters or leaves a motor module. Then, the thrust expression is deduced based on the new field orientation, and a coefficient is proposed to present the thrust bias in a single module. The restraint of the thrust bias is implemented by increasing or changing the slip frequency according to the orientation in the movement. The proposed coefficient and the thrust control method are validated by simulation and experiment results.

Impedance Matrix and Parameters Measurement Research for Long Primary Double-Sided Linear Induction Motor

Static longitudinal end effect caused by truncated iron and coil windings is the inherent characteristic of linear motors. For multisegment long primary double-sided linear induction motors (DLIMs), subsection power supply mode results in longer iron than excited coil windings, which aggravates the static longitudinal end effect. First, the characteristics of the DLIM impedance matrix are researched through experiments. The impedance matrix is calculated by the measured amplitude and phase of the three-phase voltage and current. Unlike the traditional rotating induction motor, the matrix of DLIM is not a traditional cyclic symmetric matrix. Positive-sequence impedance, which is defined and obtained based on the impedance matrix, could be used to measure parameters by open-circuit and short-circuit experiments. The parameters measurement method is validated more accurate than the traditional average phase impedance. The research results, which are validated by test data from the long primary DLIM system capable of producing 400 kN of force, operating at the 100-MW peak power level, could be the reference for accurate description of the dynamics motor model and parameter measurement.

Investigation of cogging forces using reluctance circuits equivalent approximation in a ladder secondary single­sided linear induction motor

Linear induction motors have recently played an important role in positioning linear motion. However, they suffer a low level of precision for very low speed application. For improving the precision of LIM, especially in very low speed application – high-performance motor – the existence of cogging forces due to the magnetic conductance of air gap variation or interactive magnetic edge and end effect variation in the ladder-secondary single-sided linear induction motor (LSLIM) should be reduced as small as possible. This paper developed two simple magnetic circuits: one-slot and multi-slot model. The cogging forces analysis will be concerned with magnetic energy variation in the air gap. Based on magnetic conductance inparalleland series structures, analysis of RCE will be done by implementation of Kirchoff law number one and number two. It shows that analytical result trends are close to the experimental results and finite element method software. This paper provides the prediction of a close form of the mathematical model of maximum cogging forces for single-side linear induction motors. So, those results can contribute one aspect in related designing a physical single or double-sided linear induction motor. The variation of flux densities in the air gap in the middle region of LSLIM can give some contribution for calculating cogging forces, and different variation of leakage magnetic path fields in the end region can reduce the magnitude of flux densities in the air gap, but cogging forces in the end region can cancel each other