Permanent Magnet Eddy Current Couplings Research Articles

Online Magneto-Thermal Coupled Model of PMECCs Using Measured Boundaries

Online modeling of the magneto-thermal coupled field (MCF) in permanent magnet eddy current couplings (PMECCs) has long been challenging since it exists in the copper layer and cannot be directly measured. This article proposes an online magneto-thermal coupled model (OMCM) to reconstruct the MCF using measured boundaries. The magnetic field (MF), eddy current field (ECF), and temperature field (TF) in the MCF are coupled in an identical space-time united discretization system. Virtual boundary nodes are added to the system, which can adapt to different boundary conditions in electromagnetic and thermal analysis. The measured data of single-point sensors are spanned to continuous boundary conditions. An approximate solution of the MCF is derived based on the measured boundaries and the general solutions of Laplace's equation and Poisson's equation in magneto-thermal analysis. The three-dimensional distribution of the MF, ECF, and TF at each spatial node and time segment can be simultaneously calculated in matrix form by the OMCM. Furthermore, the output torque is estimated and compared with the conventional methods. A verification process is carried out to assess the reconstructed results, showing that the OMCM can yield results close to the verification sensors for various slips and air gaps.

Modelling and analysis of the intersecting axis permanent magnet eddy‐current coupler

AbstractThe permanent magnet eddy‐current coupler (PMEC) is a kind of non‐contact, stepless speed regulation device and has been widely used in transmissions. However, the current PMECs are coaxial and cannot achieve transmission and speed regulation in intersecting axes. An intersecting‐axis permanent magnet (PM) eddy current coupler (IPMEC), which consists of a disk‐type PM rotor and a barrel‐type conductive sheet (CS) rotor arranged with intersecting axes, is proposed. It generates eddy currents through the speed difference between the two rotors and uses the non‐contact electromagnetic force between the eddy currents and permanent magnets to transmit torque. During operation, the speed can be adjusted by altering the coupling area or air gap. A theoretical model of the IPMEC based on the equivalent magnetic circuit method is presented and verified by finite element simulation using ANSYS. Then, the effects of the pole number of the PMs, the radius of the CS rotor and the PM rotor on the performance were analysed, and the design method of the IPMEC was proposed. This study can be used to expand the application range of PMECs.

A Fully Analytical Model for the Performance Prediction of Radial Permanent Magnet Eddy Current Couplers

A Fully Analytical Model for the Performance Prediction of Radial Permanent Magnet Eddy Current Couplers

Multi-Objective Optimization Design of Permanent Magnet Eddy Current Coupler Based on SCG-BP Neural Network Modeling and the ONDX-NSGA-II Algorithm

There is a complex coupling relationship between the structural parameters and various performance indicators of a permanent magnet eddy current coupler. In order to obtain the optimal combination of structural parameters that can improve the overall performance of the coupler, it is necessary to reasonably balance the contradiction and competition among performance indicators of the permanent magnet eddy current coupler. A multi-objective optimization method for permanent magnet eddy current couplers based on scaled conjugate gradient back propagation neural network modeling, improved opposition-based learning, and normal distribution crossover operator non-dominated sorting genetic algorithm-II is proposed. The optimization results are compared with those of the traditional non-dominated sorting genetic algorithm-II and the Pareto envelope-based selection algorithm-II, and it is verified that the proposed multi-objective optimization algorithm is accurate, reliable, and has better convergence and versatility. Compared with the original model, the output torque of the optimized coupler increased by 8.54%, and the eddy current loss and cost decreased by 3.71% and 8.74%, respectively. Finally, the correctness of the theoretical analysis was verified through 3D finite element simulation and an experimental simulation platform.

A Review of Recent Developments in Permanent Magnet Eddy Current Couplers Technology

Permanent magnet eddy current couplers (PMECCs) have the characteristics of contactless torque transmission, removal of torque ripple, smooth dynamic process, and adjustable speed, and can be used as couplings, dampers, brakes, and speed governors. Their applications in industry, vehicles, and energy fields are gradually expanding. At the same time, the requirements for the torque density and dynamic performance of PMECCs are increasing. Therefore, a large amount of research work has focused on the fast and accurate modeling, design, and optimization of PMECCs. This paper provides a survey on the development of PMECCs technology. The main topics include the structure and classification of PMECCs, modeling methods, loss and heat transfer analysis modeling, and optimization design. In addition, this paper shows the future trends of PMECCs research. All the highlighted insights and suggestions of this review will hopefully lead to increasing efforts toward the model’s construction and the optimal design of PMECCs for future applications.

Comparison of Eddy Current Coupling Topologies for High Efficiency Mechanical Power Transmission

The paper is an investigation into permanent magnet eddy current couplings for high efficiency power transmission. Through extensive simulation studies, the performance of radial- and axial-field topologies, employing squirrel cage and conducting sheets, are compared in terms of torque transmission density and efficiency of power transmission. It is shown, that although using a conducting sheet (as it is often the case) results in higher torque transmission density, employing a squirrel cage is more suitable for high efficiency power transmission. A prototype of the proposed radial-field single sided permanent magnet eddy current coupling employing a copper squirrel cage is developed and tested, and a good agreement between measurements and predictions is demonstrated.

Analytical Analysis of a Novel Flux Adjustable Permanent Magnet Eddy Current Coupling with Double-Sided Conductor

The permanent magnet eddy current coupling is widely used in fan and pump equipment as an energy-saving speed control device. The traditional coupling speed adjustment method occupies too much axial space, limiting its application in the process of upgrading old equipment. This paper proposes a novel flux adjustable permanent magnet eddy current coupling with a double-sided conductor to reduce the coupling axial distance while increasing the coupling output torque. The relative angle between the permanent magnet rings is controlled to adjust the output torque, and the double-sided conductor structure is used to improve the output torque. The working principle of the proposed design is illustrated. An analytical model for estimating the regulation performance of the proposed structure is proposed, which introduces the regulated reluctance into the equivalent magnetic circuit method. Based on this model, the expressions for magnetic flux density, eddy current density, and output torque are established. Finally, the accuracy of the analytical model was verified by the 3D finite element method, and the parameter sensitivity analysis was performed. The analysis results show that this device can achieve a relatively large range of output torque regulation under the condition of a fixed air gap, and the output torque is greatly improved by adopting a double-sided conductor structure.

Design and torque calculation of permanent magnet eddy current coupling with sinusoidal torque output

Design and torque calculation of permanent magnet eddy current coupling with sinusoidal torque output

Design Optimization of Permanent Magnet Eddy Current Coupler Based on an Intelligence Algorithm

Design Optimization of Permanent Magnet Eddy Current Coupler Based on an Intelligence Algorithm

In Situ Magnetic Field Reconstruction and Torque Estimation for PMECCs

Permanent magnet eddy current couplings (PMECCs) are widely used in industry to transmit torque through their interior magnetic field. It is important to measure the interior magnetic field of a PMECC, which helps ensure its excellent performance and prevent possible accidents. However, the distribution of magnetic fields is difficult to reconstruct <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> by traditional measuring or modeling approaches. This article proposes a method to continuously reconstruct the distribution of interior magnetic fields and estimate the relative parameters in a short time with a limited number of Hall sensors. A model of field-associated reconstruction (FAR) is proposed to reconstruct the distribution of interior magnetic fields using historical data and sensor positions as constraints. The slip and output torque can be estimated based on the FAR without the need to use additional speed–torque sensors. The experimental results verify the performance of the proposed method. The results show that the model performed well in the reconstruction of axial and tangential components and relatively well near the geometric boundary in the reconstruction of radial components. The relative errors in the speed and torque estimations are approximately 4% and 6%, respectively. The limitations and corresponding reasons are also discussed.

Analysis of a novel flux adjustable axial flux permanent magnet eddy current coupler

Permanent magnet eddy current couplers have been widely used in large fan and pump loads to achieve the purpose of speed regulation and energy saving. In order to reduce the coupler axial volume and simplify the actuator, a novel flux adjustable axial flux permanent magnet eddy current coupler (FAAF-PMECC) is proposed in this paper. The permanent magnet rotor is divided into three parts: the inner, middle and outer parts, where the permanent magnets are embedded in the core and the adjacent poles are magnetised in opposite directions. The middle part is the adjusting permanent magnet ring (AR), which can rotate around the shaft. The inner part and outer part are fixed permanent magnet rings (FR) that are fixed with the shaft, and the output torque can be controlled by adjusting the relative angle of AR and FR. The structure and working principle of FAAF-PMECC are described in detail, and the output torque analytical model of the whole regulating process is established based on the magnetic equivalent circuit method. The AR regulation process is simulated by the variable reluctance model. The validation results show that the proposed structure can achieve a good speed regulation effect, and the output torque calculated by the analytical model in a certain slip speed range matches well with the output torque obtained using the 3D finite element method and experimental measurements. The sensitivity analysis of the structure parameters is also carried out. The analysis shows that the proposed coupler can achieve a wide speed range.

A Performance Prediction Model for Permanent Magnet Eddy-Current Couplings Based on the Air-Gap Magnetic Field Distribution

In this article, a clear analytical model for predicting the performance of permanent magnet (PM) eddy current couplers is proposed. The interaction of the reaction magnetic fields between adjacent eddy current rings was considered for the first time. Based on a magnetic equivalent circuit (MEC) and the Ampere circuital theorem, the accurate distribution of the air gap magnetic field under different slip velocities was deduced in a 2-D model, and the analytical expression of the transmission torque was obtained. 3-D effects were also taken into account to calibrate the model. The validity of the analytical model was verified by comparison with results from the 3-D finite element method (FEM). The comparison shows that the analytical model can accurately predict the magnetic field distribution and transmission torque over a wide range of slip velocity variations. This model can greatly reduce the number of calculations required and save time, and it is suitable for the preliminary design and optimization of PM eddy current couplers.

The Analytical Comparative Analysis of Electromagnetic Characteristics of Four Typical Radial Flux Permanent Magnet Eddy Current Couplers

The analytical model of a permanent magnet eddy current coupler (PMECC) is mainly used for evaluation of its characteristics and the initial optimization of design. Based on the equivalent magnetic circuit method, this paper carries out analytical modeling for four typical PMECCs composed of surface-mounted and interior permanent magnet, slotted and non-slotted conductor rotors, which provides a theoretical basis for the subsequent research in this paper. The basic electromagnetic characteristics of the PMECCs are investigated by the established analytical model. Simultaneously, the analytical results about permeance, flux density, torque and power are verified by FEA simulation. The analysis results show that the slotted CR will obtain a much higher power density, and the iron loss mainly exists in the CRs. In addition, the analytical and FEA results agree well, which proves the reliability of the proposed, nearly unified analytical model.

Design optimization of APMEC using chaos multi-objective particle swarm optimization algorithm

In order to meet the requirement that the permanent magnet eddy current coupler has larger output torque and smaller eddy current loss in actual operation, the structural parameters and operation performance of axial permanent magnet eddy current coupler (APMEC) are optimized by chaos multi-objective particle swarm optimization algorithm (CMOPSO) in this paper. The model of APMEC is established by three-dimensional finite element simulation. The central composite design (CCD) method is used to select the appropriate test point, and the response value is obtained by ANSYS finite element analysis software simulation. The second-order response surface regression model of APMEC was established according to the response value. The CMOPSO is used to optimize APMEC, and the optimal combination of structural parameters is obtained. By comparing the eddy current density distribution of APMEC before and after optimization with the finite element simulation experiment, it is verified that the optimization method is feasible to optimize the structural parameters of APMEC. The optimization results show that the efficiency of the permanent magnet eddy current coupler is more than 94%, and the energy consumption is reduced to 83% of the original energy consumption.

A novel method for modeling the air gap flux density of the axial-flux permanent magnet eddy current coupler considering the end-effect

The virtual equivalent line method for the axial-flux permanent magnet eddy current coupler is proposed in this paper to solve the problem of the difference in the length of the magnetic flux path between the inner radius and outer radius of the axial section of the radial centerline of the magnetic pole. Different from the average radius equivalent method, the virtual equivalent line method adopts the function of variable pole radius instead of the fixed average radius, which establishes a uniform analytical expression of the air gap flux density and can accurately calculate the magnetic flux density at any magnetic pole radius. Furthermore, the end-effect compensation function is obtained. In order to investigate the effectiveness of the proposed method, the results calculated by the analytical method are compared with the finite element method. It is shown that the novel method proposed in this paper is highly consistent with the air gap flux density calculated by the finite element method.

Evaluation and analysis of novel flux‐adjustable permanent magnet eddy current couplings with multiple rotors

This article proposes a novel flux-adjustable permanent magnet eddy current coupling with multiple rotors. According to the different functions, the permanent magnet rotors are divided into fixed-flux and flux-adjustable rotors. By adjusting the relative position between two types of permanent magnet rotors, the magnetic field, torque, and output speed are controlled without changing the air-gap length. To quickly and easily analyse the torque performance, an analytical model for the torque of such devices is developed based on the non-linear magnetic equivalent circuit approach. In the modelling phase, a number of factors are considered, such as the skin effect, the inductance of eddy current field, the temperature effect, and so on. A three-dimensional finite element method is employed to validate the model results, and the comparative analysis shows the advantages and potential of the proposed topology. The further sensitivity analysis of the key parameters is also made, which offers helpful information for the preliminary design of such devices.

Analytical Prediction and Analysis of Electromagnetic-Thermal Fields in PM Eddy Current Couplings With Injected Harmonics Into Magnet Shape for Torque Improvement

To improve the output torque in permanent magnet (PM) eddy current couplings, a new structure based on harmonics injection into the magnet optimization theory is proposed. Then, a novel analytical electromagnetic-thermal model is established that can accurately reflect the 3-D distributions of the magnetic field and the eddy current. With the proposed analytical model, the eddy current loss, temperature distribution, torque characteristics and influence of the temperature rise caused by load increases on the torque are predicted and analyzed precisely. The maximum output torque can be improved by 11.22% with injected harmonics into the magnet shape. On this basis, an optimal design of the conductor plate structure is presented, based on the electromagnetic-thermal analytical model. An additional 13.05% torque improvement can be obtained, which leads to better torque characteristics and overload capability. Verification is conducted by a 3-D finite element analysis and measurements. The analytical model solves the multiphysics coupling analysis problem of PM eddy current couplings, and provides a fast and accurate calculation method to perform electromagnetic-thermal coupling analysis.

Modeling and Performance Analysis of an Axial-Radial Combined Permanent Magnet Eddy Current Coupler

The structure and magnetic circuits of axial-radial combined permanent magnet eddy current couplers are more complicated than those of axial or radial permanent magnet eddy current couplers, the degree of coupling is deeper, which will affect the device performance. In this paper, a novel analytical model for an axial-radial combined permanent magnet eddy current coupler is proposed based on the equivalent magnetic circuit method. The distribution of the magnetic field, the relationship between the slip and torque, the influence of the structural parameters on the transmission performance, the 3-D correction and thermal compensation are studied. Combined with the concept of the micro-element method, the air gap magnetic density, eddy current density and torque are accurately calculated, which solves the problem that the existing model cannot analyse the axial-radial combined structure. To show the effectiveness of the proposed analytical model, the transmission performance of an axial-radial combined permanent magnet eddy current coupler prototype is investigated, and the analytical calculation results are compared with the results of the finite element method simulations and experimental tests.

Performance Prediction and Analysis of Adjustable-speed Permanent Magnet Eddy-current Couplings

This paper presents an accurate yet simple analytical model to predict the torque characteristics of an adjustable-speed permanent magnet eddy-current coupling in the low slip working area. Based on an improved magnetic equivalent circuit method, the flux density is quantitatively calculated, and then the general explicit expression of electromagnetic torque is developed. Moreover, the saturation effect of ferromagnetic materials and the restricted slip have been reasonably taken into account. Compared with the 3-D finite element analysis and measurement results, the validity of this model is confirmed. In addition, several important parameters of such devices are analyzed and discussed.

Analytical Analysis of an Adjustable-Speed Permanent Magnet Eddy-Current Coupling With a Non-Rotary Mechanical Flux Adjuster

This paper proposes an adjustable-speed permanent magnet eddy-current coupling with a non-rotary mechanical flux adjuster (MFA) to regulate the speeds of large pump and fan for energy saving. The slip speed of the proposed coupling can be adjusted by shifting MFA along the axial direction. The structural feature and operation principle of the coupling are illustrated and addressed. A magnetic equivalent circuit model is established for analyzing the electromagnetic characteristics of the coupling efficiently. The air-gap magnetic fields, eddy-current densities, and torque–slip characteristics are investigated under different shifting distances of MFA, which reveals the fairly good torque regulation effects. The torque regulation range reaches to about 90% of the maximum torque, which indicates that the coupling can achieve a large speed regulation range by using the relatively simple approach.