A Simple Method for Performance Prediction of Permanent Magnet Eddy Current Couplings Using a New Magnetic Equivalent Circuit Model
TL;DR: A simple and practical magnetic equivalent circuit (MEC) based analytical technique for calculating the performance parameters of the permanent magnet (PM) eddy current coupling is presented and shows that in a considerably wide range of slip speeds, the torques predicted by the presented method match well with those obtained by both the three-dimensional finite element analysis and experimental measurement.
Abstract: A simple and practical magnetic equivalent circuit (MEC) based analytical technique for calculating the performance parameters of the permanent magnet (PM) eddy current coupling is presented. In the proposed MEC model built with the lumped parameters, the eddy current effects are inherently taken into account by introducing a branch magnetic circuit allowing for the magnetomotive force and the reaction magnetic flux. A complete formulation for the reaction flux which is treated as a kind of leakage flux is derived. A verification process is conducted and it is shown that in a considerably wide range of slip speeds, the torques predicted by the presented method match well with those obtained by both the three-dimensional finite element analysis and experimental measurement. The new MEC-based method also proves to be effective in the performance simulation of the PM eddy current coupling with different design parameters. In addition, the limitation of the proposed approach is also discussed and the reasons are fully investigated.
Citations
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TL;DR: This paper proposes a new equivalent magnetic network (EMN) model for vehicular dual-permanent-magnet vernier (DPMV) machines by applying a generalized modeling method and a meshing solution for oblique region to enhance modeling flexibility.
Abstract: This paper proposes a new equivalent magnetic network (EMN) model for vehicular dual-permanent-magnet vernier (DPMV) machines by applying a generalized modeling method. First, the magnetic circuit method and the meshing method are combined together to improve the modeling efficiency of the DPMV machine. The magnetic circuit method is used to generate conventional lumped parameter permeances to shorten time consumption, whereas the mesh method is utilized in disordered magnetic fields to obtain high precision. Second, a meshing solution for oblique region is proposed to enhance modeling flexibility. Moreover, the flux distributions in meshes are represented without magnetic field pre-delineation, which enables its utilization as a self-adaptive reluctance network model in design optimization. Finally, the proposed EMN model is used to predict the performance of the DPMV machine, considering leakage magnetic flux, local iron saturation, and magnetic field modulation effect simultaneously. Meanwhile, the effectiveness of the proposed EMN model is verified by comparison with finite-element analysis and experimental tests.
39 citations
Cites background or methods from "A Simple Method for Performance Pre..."
...Besides, the EMN method was usually employed as a fast analysis tool [15], computational expanses and developing process resulting from complicated model are considered as the disadvantage of EMN method....
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...The equivalent magnetic network (EMN) method has been investigated in magnetic field predictions and machine designs for decades [10]–[15]....
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...Additionally, due to the influences of on-load winding currents, the conventional EMN model cannot be employed universally under no-load and on-load conditions [9], [15]....
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...Analytical techniques were introduced into EMN method for calculating the machine performance precisely and rapidly [15]....
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TL;DR: A modular modeling method is presented, and then the optimal design of PM machines can be investigated without repetitive programming and modeling, and the accuracy and effectiveness of the proposed EMN model are verified through comparisons with finite element analysis and experimental tests.
Abstract: This paper proposes a novel mesh-based equivalent magnetic network (EMN) model for performance analysis and optimal design of permanent magnet (PM) machines. The key contribution of the EMN model is that a generalized air-gap model solution is proposed by considering the machine motion of PM machines. Meanwhile, a modular modeling method is presented, and then the optimal design of PM machines can be investigated without repetitive programming and modeling. Two kinds of mesh elements are comprehensively utilized in the EMN model, and a hybrid rotor PM (HRPM) machine with interior PM and surface PM configuration is selected as an example to illustrate the development processes of EMN model. Meanwhile, the electromagnetic characteristics of HRPM machine are calculated by the proposed EMN model, such as back electromotive force, air-gap flux density distribution, and average torque. Finally, the accuracy and effectiveness of the proposed EMN model are verified through comparisons with finite element analysis and experimental tests.
28 citations
TL;DR: In this article, a new magnetic equivalent circuit (MEC) model was presented to predict torque characteristics and reaction flux in slotted-type eddy-current couplings (SECs).
Abstract: In this article, a new magnetic equivalent circuit (MEC) model was presented to predict torque characteristics and reaction flux in slotted-type eddy-current couplings (SECs). The magnetomotive force and reaction field caused by eddy current in the conductor were innovatively introduced into the model; particularly, the modulations of the magnetic field and eddy current by iron teeth in conductor disk were taken into account by dividing magnetic flux paths in air gap into several branches. The expressions of magnetic flux and torque were obtained by combining Kirchhoff’s law and Ampere’s loop law. The torque was calculated using the method proposed and was compared with those obtained by the 3-D finite element method (FEM) and experiment, respectively. The results indicated that the method proposed is accurate and effective under conditions of low slip speeds and short air gap lengths.
23 citations
Cites background or methods from "A Simple Method for Performance Pre..."
...In [18], a new MEC model considering the reaction field of eddy current was developed and can be used to calculate eddy current reaction effects effectively....
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...As for the region τs1 < x < τm/2, the reaction field generated by the left eddy current is counteracted by itself [18] since the real reaction field is provided only by the eddy current on the right-hand side....
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TL;DR: A model of the permanent magnet retarder for braking torque at different speeds considering the skin effect, the magnetic leakage, and the actual path of the eddy currents is proposed.
Abstract: Braking torque is the most important performance parameter for a permanent magnet retarder used in heavy vehicles. This paper proposes a model of the permanent magnet retarder for braking torque at different speeds considering the skin effect, the magnetic leakage, and the actual path of the eddy currents. Based on the magnetic equivalent circuit and the piecewise function method, the static and the transient air-gap flux density models are established, and their accuracy is verified by comparison to the finite element method (FEM). The permeability distribution curve of the retarder stator is obtained by a simple permeability-measuring instrument, considering the skin effect on the permeability of the stator. Thus, the effective permeability function of the stator is obtained at different rotational speeds, and the transient air-gap flux density model is optimized using the effective permeability function. The simulation results showed that the optimized transient air-gap flux density of the calculation model was in good agreement with the FEM. Finally, the calculation model of the eddy current braking torque was verified by the bench test.
21 citations
TL;DR: A contactless, eddy-current-based speed sensor is proposed for applications where the speed of a smooth conductive surface is to be measured; but contact to or modification of this target surface is prohibited.
Abstract: Speed sensing is an essential part in all closed-loop systems. There exist some situations in industry where the speed has to be measured without touching the target object, for example, the accurate speed measurement of the solid metal wheels with smooth surfaces of freight wagons. In this article, a contactless, eddy-current-based speed sensor is proposed for applications where the speed of a smooth conductive surface is to be measured; but contact to or modification of this target surface is prohibited. The proposed speed sensor is composed of a permanent magnet (PM) rotor that is free to rotate above the target surface. The relative motion of the surface with respect to the PM field induces eddy currents in the surface, which leads to a torque being applied on the rotor. Consequently, the PM rotor speeds up until it reaches a steady rotational speed that is proportional to the speed of the target surface. Three models are proposed. They are a two-dimensional (2-D) finite-element model, a 2-D analytical model, and a three-dimensional (3-D) combined numerical/analytical model. Measurements are taken on multiple hardware prototypes to validate the analysis. Finally, a multiobjective (PM volume vs. dynamic performance) Pareto optimization is conducted for the proposed speed sensing system. The results show that smaller rotors with lower pole-pair numbers generally have better dynamic performance as well as lower costs.
18 citations
References
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01 Apr 1958
TL;DR: In this paper, the problem of estimating the power losses in a cylindrical corrosion-resistant shell of a fly-by-fly RC motor is investigated. But the results are limited to the case where the rotor is separated from the stator by a thin, corrosion resistant shell.
Abstract: The problem of circulating corrosive liquids assumes a major importance in nuclear-engineering practice, where the standards of safety and reliability which are imposed demand sealed circulating systems. One method employs a completely enclosed centrifugal pump driven by a squirrel-cage induction motor in which the rotor is separated from the stator by a thin cylindrical corrosion-resistant shell which is situated in the air-gap of the machine and effectively forms part of the retaining wall of the circulating system. A precise assessment for design or development purposes depends on a knowledge of the power losses in the stationary shell and it is a solution of this eddy-current problem which is developed in this paper. Arguments more appropriate to field theory than to circuit theory lead to a classical boundary-value problem which takes into account the nature and thickness of the shell and the length of overhang, and provides formulae for current densities, flow lines and dissipated power in terms of ordinary machine parameters and the dimensions and electrical constants of the shell. Theoretical and practical results are compared and shown to be in close agreement. Some of the graphical results display a pronounced slot effect and suggest methods for making a more detailed investigation. The theory can be extended to correspond to a composite shell of complex structure and it has some bearing on the principles employed in drag-cup motors, to which it could be applied.
221 citations
TL;DR: In this paper, a methodology for constructing a state-variable model, based on a magnetic equivalent circuit of the motor, is described, which is an excellent compromise between the speed of lumped parameter models and the ability of finite element methods to capture spatial effects.
Abstract: Finite element models are invaluable for determining expected machine performance. However, finite element analysis can be computationally intense; particularly if a large numbers of studies or high bandwidth studies are required. One method to avoid this difficulty is to extract machine parameters from the finite element model and use the parameters in lumped parameter models. While often useful, such an approach does not represent space harmonics or asymmetries in the motor. A methodology for constructing a state-variable model, based on a magnetic equivalent circuit of the motor is described herein. In addition, the parameters for this model are based solely on geometrical data. This approach is an excellent compromise between the speed of lumped parameter models and the ability of finite element methods to capture spatial effects. Experimental validation of the model is provided.
160 citations
TL;DR: The flux produced by stator winding currents and PMs can be calculated accurately and rapidly using the developed model, taking saturation into account, and aids machine dimensioning without the need for computationally expensive finite-element analysis.
Abstract: This paper proposes a generalized equivalent magnetic circuit model for the design of permanent-magnet (PM) electric machines. Conventional approaches have been applied to PM machine design but may be insufficiently accurate or generalized without taking pole-slot counts into consideration. This would result in reduction of dimensioning accuracy at the initial design stage. Also, magnetic saturation is often ignored or compensated by correction factors in simplified models since it is difficult to determine the flux in individual stator teeth. In this paper, the flux produced by stator winding currents and PMs can be calculated accurately and rapidly using the developed model, taking saturation into account. A new modeling technique for PM poles is proposed so that the magnetic circuit is applicable to any pole-slot combinations. This aids machine dimensioning without the need for computationally expensive finite-element analysis (FEA). A 540-kW PM machine is first designed using the proposed method and then verified with FEA. Another 350-W machine is subsequently designed, manufactured, and validated by both FEA and experiments. The comparisons demonstrate the effectiveness of the proposed model.
141 citations
TL;DR: An analytical model is developed, which is able to deal with the complex machine geometry and take into account material properties such as iron saturation and PM characteristics, which shows several advantages in terms of mechanical and magnetic performances over the couplers with surface PMs.
Abstract: Analytical calculations are effective in preliminary design stages and analysis of electric machines. In this paper, for axial-flux interior permanent-magnet (PM) eddy-current couplers, an analytical model is developed, which is able to deal with the complex machine geometry and take into account material properties such as iron saturation and PM characteristics. The design considerations of the machine are also presented. Moreover, the studied structure shows several advantages in terms of mechanical and magnetic performances over the couplers with surface PMs. The three-dimensional (3-D) finite-element method is employed in the analyses and evaluations. Finally, an experimental prototype is built to validate the model.
108 citations
"A Simple Method for Performance Pre..." refers background or methods in this paper
...However, the eddy current and its reaction field should be taken into account in the theoretical analysis of the PM eddy current coupling, which requires some additional treatments as the supplement to the eddy current free MEC model [24]....
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...In recent years, there have been several reports on analyzing eddy current couplings or brakes by partly [22], [23] or fully [24] using the MEC model in which the eddy current effects were all not distinctly represented....
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TL;DR: In this paper, a detailed analytical study of rotational eddy-current couplers is presented, which consist of a permanent-magnet stator and a multilayer conductive rotor.
Abstract: We present a detailed analytical study of rotational eddy-current couplers. We provide a field solution by the variable separation method, and we analyze radial geometry structures. The couplers consist of a permanent-magnet stator and a multilayer conductive rotor. We present different analytical solutions in order to study single- and double-sided permanent-magnet frames. We validate the models by two-dimensional and three-dimensional (3-D) finite-element studies, and we perform an exhaustive parametric analysis to estimate the influence of the dimension parameters of the two structures. Finally, we present an analytical approach to a 3-D correction.
93 citations