Flux Linkage Characteristics Research Articles

Current Profiling Control for Torque Ripple Reduction in the Generating Mode of Operation of a Switched Reluctance Motor Drive

The benefits of utilizing Switched Reluctance Motor (SRM) drives in traction applications can be realized fully by improving the electromagnetic performance of the machine in the generating mode of operation. This is because the generating capability of an SRM drive could be utilized for regenerative braking and also for the machine to generate power for the vehicle while the engine is in operation. In this paper, a current profiling-based control strategy is proposed to reduce the torque ripple in an SRM drive in the generating mode. The reference current profile is determined using a multi-step computation method to minimize torque ripple and maximize the average torque. The reference current profile is derived based on the reference torque command by utilizing the torque–current–angle look up table. The flux linkage characteristics of the SRM are considered when deriving the phase reference current profile. Then, the performance of the proposed profiling method, analytical linear and cubic torque sharing functions (TSFs), and the average torque optimization scheme are compared using simulation results. Finally, an experimental correlation is performed to validate the efficacy of the proposed control scheme.

A Semi-Analytical Method for Obtaining the Flux-Linkage Characteristics of Mutually-Coupled Switched Reluctance Machine

A Semi-Analytical Method for Obtaining the Flux-Linkage Characteristics of Mutually-Coupled Switched Reluctance Machine

Calculation method of external fault short-circuit current for variable-speed pumped storage units based on time-domain dynamic circuit

The calculation method of the external fault short-circuit current of large units with clear mechanisms and practicality is of great value in engineering practice. Due to the special AC excitation structure and control mode, the external fault short-circuit characteristics of variable-speed pumped storage units (VSPSUs) are very different from those of conventional units. Therefore, this paper proposes a calculation method for external fault short-circuit current based on a time-domain dynamic circuit. According to the excitation and control characteristics of VSPSUs under external fault, the VSPSU under external fault is divided into two cases: continuous excitation and jumper action. Based on space vector analysis, the time-domain dynamic circuit models are established, respectively. On this basis, the analytical formula of the external fault short-circuit current of VSPSUs is derived by combining the transition boundary conditions of the two cases and the dynamic characteristics of the stator flux linkage. Finally, the comparison with PSCAD/EMTDC simulation results shows that the proposed VSPSUs’ external fault short-circuit current calculation method has high accuracy and practical value, which can meet the needs of primary equipment selection and relay protection of variable-speed pumped storage power plants.

Modeling of nonlinear characteristics of switched reluctance motor based on optimized RBF neuron network

The strong nonlinearity of switched reluctance motor (SRM) makes it difficult to establish an accurate mathematical model of its electromagnetic characteristics. In this paper, an artificial neural network modeling method is adopted to estimate the nonlinear flux linkage characteristics of a four-phase SRM. Based on the samples obtained by experimental measurement, a radial basis function neural network is trained and further optimized using the K-Means algorithm. The modeling accuracy of the optimized flux linkage model is analyzed in detail and also verified by dynamic simulation of a direct instantaneous torque control system of the motor.

Analytical Prediction of Static Flux-Linkage Characteristics of Switched Reluctance Machine

This paper deals with the analytical prediction of static flux-linkage characteristics of switched reluctance (SR) machines, which have emerged as competitive candidates in various applications, including automotive, aerospace, machine tools, and renewable energy. Specifically, this paper proposes a novel flux-tube-based approach to derive closed-form analytical expressions for the effective air-region permeance at the aligned and unaligned rotor positions in terms of machine dimensions. The proposed method does not require preliminary finite element analysis (FEA) and includes the effect of rotor pole height on the effective air-region permeance. The predictions by the proposed method are compared with the results of FEA and three existing analytical methods, considering seven different SRM designs and different sets of machine dimensions. The results of the proposed method are found to be accurate and comparable to those of FEA in all cases. Further, based on magnetic material characteristics and machine dimensions, the static flux-linkage characteristics at the aligned and unaligned rotor positions are predicted. The aligned and unaligned flux-linkage characteristics of a 10000-rpm, 5-kW SR machine, thus predicted, are verified through FEA and experiments. As an application of the proposed analytical method, electromagnetic design of a 40-kW, 80000-rpm, 600-V SRM is carried out and is validated through static FEA and simulations.

A New Adaptive Analytical Model for the Spherical Reluctance Motor Based on Hybrid Trigonometric Function–Power Function

To realize the multiple-degree-of-freedom (multi-DOF) motion, this paper proposes a new spherical reluctance motor (SPRM). For the nonlinear characteristics of flux linkage and excessively complex torque calculation, this paper proposes a new adaptive analytical model for SPRM based on hybrid trigonometric function-power function. A sixth-degree polynomial is used to represent the five coefficients of this model, and these coefficients are calculated from flux linkage-rotor angle-phase current data using numerical curve fitting with nonlinear least square. Based on the criterion of minimizing the Sum of Squared Error (SSE) between the flux linkage obtained by Finite Element Analysis (FEA) and the flux linkage calculated by analytical model, the optimal trigonometric function angular frequency coefficient and the optimal power function exponent are adaptively obtained by iterative algorithm. The feasibility and accuracy of this model is validated by comparing with the existing models. Furthermore, the experimental results show that the calculated torque has a good agreement with the measured torque, which further verifies the validity of the proposed analytical model. The versatility of the proposed model for SPRMs with different structure parameters is discussed as well.

Operational Diagnostics System for Asymmetric Emergency Modes in Traction Drives with Direct Torque Control

This article presents an analysis of the causes behind the development of asymmetric modes in a traction drive system that features direct torque control (DTC) of a rolling stock with asynchronous traction motors. The development of asymmetric modes in the traction drive system was found to be caused by the asymmetry of the supply voltage system, the asymmetry of the traction motor windings, and transient processes triggered by a change in the inverter supply voltage and variation in the traction motor load. At the same time, the asymmetric modes caused by the asymmetry of the feed voltage system and the windings of the traction motor are the emergency modes. The influence of the asymmetry of the feed voltage system and asymmetry of the windings of traction motor on the starting characteristics of the phase currents and flux linkages of the stator in the steady-state mode was investigated. In these cases, the ratio of the amplitudes of phase currents and flux linkages of the stator of different phases was found to be constant. The effect of a variation in the feed voltage and load acting on the motor shaft on the starting characteristics of phase currents and flux linkages of the stator was investigated in the case of absence of the emergency modes. In these cases, the ratio of the amplitudes of phase currents and flux linkages of the stator of different phases was found to not be constant. The amplitudes of the phase current and stator flux linkage were proposed as criteria for diagnosis and identification of asymmetric emergency modes. An algorithm and a structural scheme have been proposed for the diagnosis of emergency asymmetric modes in the traction drive system with direct torque control. Modifications to the traction drive system with direct torque control are suggested in order to diagnose the presence of faulty asymmetric modes and identify the damaged traction drive element.

A Novel Model Predictive Torque Control of SRMs With Low Measurement Effort

This article presents a low-measurement effort and less storage space but an effective method to reduce the torque ripple. First, a torque-balanced measurement method is presented to obtain the flux-linkage characteristics at four torque-balanced positions. Then, a four-order Fourier series model is proposed to describe the entire flux-linkage and torque characteristics. To reduce the storage space, a Polynomial-Fourier series model is proposed to describe the torque and current model from the rotor position and flux-linkage. Based on the proposed Polynomial-Fourier series model, a novel model predictive torque control (MPTC) is implemented to minimize the torque ripple with flux-linkage-based torque estimation. Experimental results show the proposed method can effectively reduce torque ripple with lower measurement effort and less storage space compared with the traditional MPTC method. Furthermore, the key issues of model predictive control, such as error analysis, weight coefficients selection, and magnetic saturation, are discussed in detail. The proposed method provides a low-effort and convenient way to implement the advanced control of SRMs in the industry application.

Lumped Radial Force Characteristics Reconstruction for Switched Reluctance Machines Through Scaling Flux-Linkage Characteristics

This article presents a simple and practical method to estimate the lumped radial force characteristics for the switched reluctance machines (SRMs). First, the relationship between the square root of the lumped radial force and the flux linkage is discussed and analyzed. With the geometry data of the studied SRM, the abovementioned relationship under nominal air-gap length and nominal material magnetic property conditions can be obtained through the finite-element analysis (FEA) software. As the radial flux density dominates the magnitude of the radial force and it concentrates on the overlapping area, the abovementioned relationship is analyzed to be roughly held when the air-gap length and/or material magnetic property vary. Based on this relationship obtained from the FEA and the actual measured flux-linkage characteristics, the lumped radial force can be easily reconstructed for the actual SRMs regardless of the possible air-gap length variation and material magnetic property deviation during the manufacturing process. Simulation results on the 8/6 SRM and 12/8 SRM verify that the proposed method provides good radial force estimation results when the air-gap length is reduced or increased up to 50%. Superior estimation results are also observed on the condition that the magnetic <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${B}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${H}$ </tex-math></inline-formula> curve is linearly varied by ±25%. The accurate and simple radial force estimation method proposed in this article provides a solid basis for the radial-force-shaping-based advanced control methods to suppress the acoustic noise.

Sensorless Position Control of Linear Electromagnetic Actuator for Gear Shift Unit

Conventional manual transmissions suffer from deterioration due to wear and reduced responsiveness. Therefore, a linear electromagnetic actuator (LEA) for gear shifting has been developed. Since the LEA is a direct drive, it prevents deterioration due to wear and has high responsiveness. In addition, this LEA has a high holding force by detent force at three points. In this paper, sensorless position estimation is performed to simplify the system. Since one coil is not energized during driving in this LEA, so the back-EMF of the unenergized phase can be measured. We propose a sensorless position estimation method that focuses on the variation of the magnetic flux linkage characteristics in the position change. The simulation results show that the sensorless position control is possible.

A Novel Method to Obtain the Flux-Linkage Characteristics of Switched Reluctance Motors

Measuring and quantifying the electromagnetic characteristics of switched reluctance motors (SRMs) are indispensable for advanced motor control and performance enhancement. This article reports on a novel method in obtaining the flux-linkage characteristics of an SRM without rotor clamping devices and position sensors. This approach combines measurement with data reconstruction. For the measuring step, flux-linkage samples at four torque-balanced positions were measured indirectly. Considering the magnetic coupling among phases, two different excitation forms were adopted to further increase accuracy. Then, for the reconstructing step, a fuzzy logic-based approach was applied to reconstruct the complete flux-linkage characteristics with measurement results. The construction results were compared to measurements results from the traditional rotor clamping method, and good agreements can be found, demonstrating the effectiveness of the proposed method. Furthermore, based on reconstructed electromagnetic characteristics, dynamic simulation of an SRM prototype under different control modes was carried out and analyzed in MATLAB. Comparison with dynamic experiments further verifies the accuracy and effectiveness of the proposed method.

Measures and Simulations of Induction Machines Flux Linkage Characteristics Based on Rotor Field Orientation

The focus of this work is on the experimental measurement and the proper finite-element prediction of stator and rotor flux linkages for induction machines. The purpose is to characterize the stator and rotor flux linkages adopting a rotor field-oriented reference frame. The proper basic set of equations is inspired by the direct field-oriented control approach, in order to indirectly derive the rotor flux linkage from the measurement of the stator flux. The proposed method requires a small set of preliminarily known parameters, such as the stator resistance and the overall leakage inductance. Moreover, the only measured quantities are voltages and currents, from which the flux linkages are derived. The adopted strategy also allows to estimate electromagnetic torque and rotor resistance, using the rotor field-oriented model equations. A complete finite-element validation reported for comparison.

Nonlinear Modeling of a C-Core Connected Two-Phase Switched Reluctance Motor

The main idea of this paper is to offer a continuous C-cores unique configuration for switched reluctance motor (SRM) and to present an analytical model for its analysis. The advantages of this structure are having a short path for the main part of the magnetic flux, resulting in less core losses and as well as less negative torque. On the other hand, there is less leakage flux in the proposed structure. Another advantage of this structure is that it has a high mean torque compared to conventional structures, so that this increase in mean torque also increases a small amount of torque ripple, which is negligible. However, power density at a constant volume increases relatively much. The proposed SRM is analyzed by the finite element method (FEM) and by employing a magnetic flux density pattern and magnetic fluxes path, its magnetic equivalent circuit (MEC) is obtained. In this MEC model, the main fluxes and leakage fluxes are fully modeled. After its complete analysis, electromagnetics torque, inductance, flux-linkage, mean torque, and peak torque are evaluated. Static and dynamic performances are then determined. Finally, the proposed SRM was prototyped and tested. The experimental results consisting of static torque, flux-linkage, voltage, and current waveforms and input power are compared with the corresponding results in the MEC model and FEM. The comparisons verify the accuracy and validity of the introduced analytical model. Besides, static torque, flux-linkage characteristics, and dynamic performance at a nominal speed of 1000 rpm and the current chopping control mode with chopping 5A under the load of the proposed SRM are compared with the conventional SRM and its merits are observed.

Comprehensive study on divided‐teeth and permanent magnet assisted outer‐rotor switched reluctance motors

A comprehensive study on divided-teeth permanent-magnet assisted outer-rotor switched reluctance motors (SRMs) is carried out. Foremost, it looks into the impact of the number of teeth per stator pole. The average and maximum torque profiles of the compared structures are obtained using finite-element simulations. It is shown that as the number of teeth increases, higher torque is obtained. Then, six small PMs are inserted inside the teeth of neighbouring modules to form new hybrid reluctance motors (HRMs). The four permanent-magnet assisted SRMs are compared in terms of the average and maximum torques using finite-element simulations. Based on the comparison results, the 48/50 HRM is selected as the best candidate among all compared SRMs and HRMs. The magnetic flux density distributions, static torque, and flux linkage characteristics of the proposed HRM are obtained. Moreover, the cogging torque profile of the motor is obtained, which approximates to zero. Next, the steady-state performances of the proposed HRM are obtained under low- and high-operating speeds. Finally, a prototype of the machine is constructed and the test results are obtained and compared with those of the simulations, which show that there is a good agreement between these results.

Improved Analytical Method to Determine Flux-Linkage Characteristics of a Switched Reluctance Machine

This article proposes an improved analytical method for accurate evaluation of flux-linkage characteristics for a given switched reluctance machine (SRM). Initially, air-gap inductance is calculated using an approximated analytical method, which incorporates the effect of fringing fluxes. Then, precepts of a conventional method are used to compute these characteristics under saturation, with a proposed new analytical model for nonuniform flux distribution in stator and rotor poles. Finally, for error quantification, these characteristics are benchmarked against those from a standard finite element analysis (FEA) based software. Both mean and standard deviation of the estimation errors are presented to quantify estimation accuracy. To establish its general validity, these characteristics are evaluated using the proposed method for six SRMs of different geometries and compared with those obtained from FEA. For further benchmarking, speed-torque characteristics obtained from the proposed method and FEA are presented and compared. Finally, both flux-linkage and torque-speed data are experimentally obtained from a 5 kW, 270 V, 12 000 r/min, 6/4 SRM and presented for validating the accuracy of the proposed method.

Edge effect of multi-degree-of-freedom oscillatory actuator driven by vector control

AbstractThis article proposes a thrust equation model of two-degree-of-freedom oscillatory actuator considering its edge effect. The proposed thrust equation model clarifies that asymmetric permanent magnet flux linkage and inductance characteristics cause undesirable magnetic thrust and reluctance thrust, respectively.

Three-Dimensional Magnetic Equivalent Circuit Research of Double-Sided Switched Reluctance Linear Machine

This paper proposes a three-dimensional magnetic equivalent circuit (3D MEC) method to analyze the flux linkage characteristics and electromagnetic force characteristics of double-sided switched reluctance linear machine (DSRLM). The 3D finite element model (3D FEM) of DSRLM is established to analyze the magnetic field line distribution of the motor. The magnetic field distribution of two representative positions (unaligned and aligned position) is mainly analyzed, and the reluctance of each part was obtained by the magnetic flux tube method. According to the similarity principle, the magnetic flux tube with irregular shape is equivalent to a simple magnetic circuit that is easy to calculate. According to the similarity of the magnetic circuit and electric circuit, the 3D MEC model of DSRLM was established. The Gauss–Seidel iteration method is used in MATLAB to solve the flux linkage-current curves at two representative positions. Then the flux linkage curves calculated by the MEC method are compared with the 3D-FEM results and experimental results. After that, the flux linkage curves obtained by MEC are used to solve the electromagnetic force curves. And the electromagnetic force curves are compared with the curves obtained by FEM and experiment. It can be found that the error is within an acceptable range, indicating that the scheme is more feasible.

Design and Analysis of a 16/6 Bearingless Switched Reluctance Motor with Segment Hybrid Rotor Teeth

In this article, a 16/6 bearingless switched reluctance motor (BSRM) with segment hybrid rotor teeth has been presented. To realize the decoupling control of torque and suspension force, the rotor teeth were divided into three torque teeth and three suspension teeth, and both of them are embedded in support part. First, both torque and suspension force are generated by short‐circuit excitation, the flux linkage coupling between torque windings and suspension windings was eliminated, and the separate control of torque and suspension force was achieved. Then, by increasing the pole arc of suspension teeth, the inductance of suspension windings is kept constant, which eliminates the influence on the output torque when adjusting suspension force. Finally, the coupling degree is further reduced by using nonmagnetic material as the supporting part. In addition, to achieve a greater output torque, the torque teeth are processed into U‐shape and optimized the pole arc of stator teeth and rotor teeth. The characteristics of inductance, flux linkage, and output torque are analyzed by the finite‐element method, and the results show that the proposed structure basically achieves the decoupling control of torque and suspension force. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Modelling of High Torque Density Switched Reluctance Motors with Mutual Coupling

In this paper a method is introduced which models the resulting motor torque and current dynamics directly from the flux linkages. With the introduced method to process the flux linkage characteristics it is sufficient to calculate half of an electrical period to receive all information for modelling the system’s behaviour, even for both long and short flux path mutual coupling. The model is validated by 2D finite

Model Predictive Control of Switched Reluctance Starter/Generator With Torque Sharing and Compensation

To enhance the mechanical safety, guarantee sufficient temperature margin and reduce the high-frequency electromagnetic interference of the starter/generator embedded in the aero engine, a multiobjective optimization control method is proposed for the switched reluctance machine based on the model prediction and the torque sharing function (TSF). For the model predictive control, the instantaneous phase torque is estimated through the Hermite interpolation with the flux-linkage characteristics at the aligned and unaligned rotor position, and the reference phase torque is obtained by the TSF. The error between the estimated and real instantaneous torque, especially around the unaligned rotor position, will result in the performance degradation, which is effectively compensated by the new TSF. The performances of the proposed control method are evaluated in detail by the simulation and experiment, and comparison with other representative methods is carried out as well.