Search

Hybrid excited machines, with synergies of permanent magnet (PM) and wound field (WF) excitations, exhibit high torque density as well as controllable flux and are perceived as promising candidate for variable speed application. A novel doubly salient hybrid excited (DSHE) machine with non-overlapped field winding is presented in this paper. It inherits simple structure of conventional doubly salient PM (DSPM) machine and facilitates the regulation of magnetic field by field winding. The electromagnetic performances of the proposed machine with different stator and rotor pole number combinations are investigated by finite element method (FEM), confirming these advantages. Furthermore, the effect of iron bridge on the hybridization between PM and WF excitations is analyzed to obtain a trade-off between high torque density and wide flux regulation range with the frozen permeability method (FPM). It is revealed that the proposed DSHE machine possesses higher power and fault tolerance at flux weakening region compared with the DSPM machine, albeit with sacrificed torque density and efficiency with introduction of field winding. Finally, a prototype is fabricated and tested to validate the theoretical analyses. [ABSTRACT FROM AUTHOR]

To solve stochastic problems with geometric uncertainties, one can transform the original problem in a domain with stochastic boundaries and interfaces to a problem defined in a deterministic domain with uncertainties in the material behavior. The latter problem is then discretized. There exist infinitely many random mappings that lead to identical results in the continuous domain but not in the discretized domain. In this paper, an a priori error indicator is proposed for electromagnetic problems with scalar and vector potential formulations. This leads to criteria for selecting random mappings that reduce the numerical error. In an illustrative numerical example, the proposed a priori error indicator is compared with an a posteriori estimator for both potential formulations. [ABSTRACT FROM AUTHOR]

The numerical solution of partial differential equations onto random domains can be done by using a mapping transforming this random domain into a deterministic domain. The issue is then to determine this one to one random mapping. In this paper, we present two methods—one based on the resolution of the Laplace equations, one based on a geometric transformation—to determine the random mapping. A stochastic magnetostatic example is treated to compare these methods. [ABSTRACT FROM PUBLISHER]

In this paper, the open-circuit dc-winding-induced voltage in a wound field switched flux (WFSFs) machines is analyzed. The phenomenon of open-circuit dc-winding-induced voltage is illustrated and the mechanism is explained. Rotor skewing is proposed to reduce the open-circuit dc-winding-induced voltage, and the optimal skewing angle is analytically derived based on the analytically deduced harmonic orders of the open-circuit dc-winding-induced voltage. Finite-element (FE) analyses show that the open-circuit dc-winding-induced voltages in the analyzed 12-stator-pole partitioned stator WFSF machines having 10-, 11-, 13-, and 14-rotor-pole rotors can be effectively reduced by >94%, while the ac-winding phase-fundamental back-EMFs can be maintained by >95%. Twelve/ten-stator/rotor-pole prototypes with skewed and nonskewed rotors are built and tested to verify the analytical and FE results. [ABSTRACT FROM AUTHOR]

DC winding induced voltage pulsation in the wound field synchronous machines (WFSMs) will cause dc winding current ripple, challenge the dc power supply, and deteriorate the control performance, especially at high speed. In this paper, the influence of dc winding configuration including the dc coil number and the parallel branch number on its induced voltage pulsation is investigated for WFSMs. Based on the modeling of both open-circuit and on-load dc winding induced voltages, the preferred dc winding configurations for WFSMs having various stator/rotor pole number combinations with double layer or single layer ac windings are obtained and validated by finite element (FE) analysis on four typical partitioned stator WFSMs (PS-WFSMs). A PS-WFSM prototype is built and tested to validate both analytical and FE analyses. [ABSTRACT FROM AUTHOR]

Novel stator slot permanent magnet (SSPM) machines with doubly salient structure have attractive features, such as a robust rotor and fail-safe capability during faults due to their peculiar PM excitation characteristics. In this paper, average electromagnetic torque production in SSPM machines is investigated using the frozen permeability analysis for the 12/10 stator/rotor pole machine. The single layer (SL) and double layer (DL) winding SSPM machines with 12/10 stator/rotor poles are further investigated, accounting for the influence of stator tooth-tips. The key findings include that the average electromagnetic torque can be enhanced by 9%–10% at the rated current for the DL and SL winding machines with stator tooth-tips. The influence of design parameters, open-circuit characteristics, inductances, electromagnetic torque, torque ripple, and losses is studied. Finally, the 2-D finite-element analysis is experimentally validated. [ABSTRACT FROM AUTHOR]

In numerical computation, the finite-element method associated with external electric circuits is often used to evaluate electromagnetic devices with voltage sources. To study the solution of the steady state, the computation time can be prohibitive due to a large transient state compared with the time step used to discretize the time domain. In this paper, a method based on the waveform relaxation method is developed in order to impose the steady state of the solution in the case of a nonlinear magnetostatic problem coupled with electric circuit equations. [ABSTRACT FROM AUTHOR]

In mass production, fabrication processes of electrical machines are not perfectly repeatable with time, leading to dispersions on the dimensions which are not equal to their nominal values. The issue is then to link the dispersions on the dimensions, which are uncertain to the performance of electrical machines in order to evaluate their influence. To deal with uncertainty, there is a growing interest in the stochastic approach, which consists of modeling the uncertain parameters with random variables. In fact, this approach enables us to quantify the influence of the variability of the uncertain parameters on the variability of the quantities of interest. In this paper, a stochastic approach coupled with a 3-D finite-element model is used to study the influence of the fabrication process imperfections, such as the rotor eccentricity and the stator deformation, on the performance of a claw pole synchronous machine. [ABSTRACT FROM AUTHOR]

The hybrid-excited stator slot permanent magnet (HSSPM) machines have good flux regulation capability due to the dc excitation. This makes them attractive candidates for variable speed applications. In this paper, the choices of stator/rotor pole combinations for an arbitrary number of armature phases are discussed. The three-phase 12-10/11/13/14 stator/rotor poles HSSPM machines with single- and double-layer windings are further investigated. Their open-circuit characteristics, torque, inductances, and unbalanced magnetic forces are comparatively studied using 2-D finite-element analysis (FEA). Finally, the 2-D FEA is experimentally validated. [ABSTRACT FROM AUTHOR]

A novel stator hybrid-excited, parallel flux path, synchronous machine of doubly salient topology is proposed. It has the novel features of: 1) hybrid dc field and permanent magnet (PM) excitation in the stator; 2) magnets placed in the slots between adjacent salient stator poles; and 3) the magnetic poles of PMs arranged, such that the flux premagnetizes the stator, but it is in a direction to oppose the dc excitation flux. The electromagnetic characteristics of the machine are analyzed on open-circuit and load. Since the new machine topology is developed from the variable-flux machine (VFM), a comparison of their electromagnetic torque and machine losses is conducted. The average electromagnetic torque of the hybrid-excited machine can be increased by 18% for fixed copper loss in comparison with the VFM due to the reduction of magnetic saturation in the stator. It is also shown that at high temperatures some risk of PM demagnetization exists when excited with dc and armature currents due to fringing flux that exists between the stator and the rotor poles. However, this affects only a very small area of the PMs. The performance of the hybrid-excited machine is predicted by a 2-D finite-element analysis and experimentally validated. [ABSTRACT FROM AUTHOR]

To solve multiphysics problems, weak coupling of finite element calculations can be carried out: the subproblems of which the physical nature differs are solved separately on their own meshes. In this case, Galerkin projection provides useful tool to ensure the transfer of physical fields between different meshes. In terms of implementation, the Galerkin projection system can be either accurately assembled over the intersection of two meshes or approximately integrated over the target mesh. This paper describes and compares these two implementation techniques for the Galerkin projection. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Coupled problems are made up of subproblems of which the physical nature differs. Using indirect coupling models, the subproblems are calculated separately on their own meshes to ensure precision. To obtain a precise solution for the total problem, it is important to ensure the transmission of information between the subproblems. In this paper, we present field projection methods on overlapping domains. In comparison to earlier works, the classical L^2 or \bf L^2 projection theory is extended to H(\bf grad), \bf H(\bf curl) and \bf H(div) to obtain increased projection accuracy for the distributional derivatives. A Petrov–Galerkin method is then presented to fill the test space using a biorthogonal basis, without losing the optimality of the result in comparison to the L^2 or \bf L^2 Ritz–Galerkin method. Using the Petrov–Galerkin method and biorthogonal test functions, the projection is presented using a diagonal matrix. However, in the standard Ritz–Galerkin projections, a linear system must be solved. [ABSTRACT FROM AUTHOR]

For a magnetodynamic problem decomposed into subdomains, the Mortar method can be associated with potential formulations to connect nonconforming meshes. In this paper, we propose to use the bi-orthogonal nodal shape functions with the Mortar method in the case of A\-\varphi formulation. Academic examples will be studied to shown the efficiency of the proposed model. [ABSTRACT FROM PUBLISHER]

An approach based on the double Lagrange multipliers is developed using the finite element method in order to impose complex periodic or anti-periodic boundary conditions. The magnetostatic equations are solved using the vector or scalar potential formulations. In order to show the possibilities of the proposed approach, an example of application is studied and the results are discussed. [ABSTRACT FROM AUTHOR]