Search

This article systematically compares two axial flux permanent magnet machines designed for a university student racing car application: a double-rotor single-stator yokeless and segmented armature (YASA) structure, and a single-stator single-rotor configuration. Both machines are optimized for minimum loss and active weight using three-dimensional finite element analysis and the highest performing candidate designs are compared in more detail. The studies indicate that the benefits offered by the YASA configuration over the single-stator single-rotor machine are achieved only for specific designs that are heavier. For the design space with lower mass, albeit with increased losses, the Pareto front designs overlap. In this envelope, the YASA configuration demonstrates higher efficiencies at higher speeds, whilst the single-stator single-rotor is more efficient in high torque duty cycles. This shows the performance of the two machines is very similar and the choice is application specific. To validate the finite element analysis used in the optimization, a prototype was built and tested. Results showed good alignment between simulation and experimental data. [ABSTRACT FROM AUTHOR]

This article proposes a new hybrid analytical and numerical finite element (FE) based method for calculating ac eddy current losses in wire windings and demonstrates its applicability for axial flux permanent magnet electric machines. The method takes into account three-dimensional (3-D) field effects in order to achieve accurate results and yet greatly reduce computational efforts. The new 3-D FE-based method is advantageous as it employs minimum simplifications and considers the end turns in the eddy current path, the magnetic flux density variation along the effective length of coils, and the field fringing and leakage, which ultimately increases the accuracy of simulations. This study is one of the first ones to compare meticulous 3-D finite element analysis (FEA) models with more approximate, but faster solution methods, which can be employed in the optimization process. The accuracy of the 3-D FEA calculations has been confirmed through tests on a prototype axial flux permanent magnet machine. The proposed method is applicable for cases with majority of ac copper losses induced due to external magnetic flux sources, such as permanent magnets. Examples of such machines designs are coreless or open slot PM machines with conductors sizes smaller than skin depth. [ABSTRACT FROM AUTHOR]

Optimizing the design of electric machines is a vital step in ensuring the economical use of active materials. The three-dimensional (3-D) flux paths in axial flux permanent magnet (AFPM) machines necessitate the use of computationally expensive 3-D electromagnetic analysis. Furthermore, a large number of design evaluations is required to find the optimum, causing the total computation time to be excessively long. In view of this, a two-level surrogate assisted algorithm capable of handling such expensive optimization problems is introduced, which substantially reduces the number of finite element analysis (FEA) evaluations to less than 200 while conventional algorithms require thousands of designs to be analyzed. The proposed algorithm is employed to optimally design an AFPM machine within a specified envelope, and to identify the limits of cost and efficiency. In order to obtain these limits, the variables' ranges are assigned to be as wide as possible, resulting in a vast design space, the study of which was enabled by the developed special algorithm. Additionally, optimized designs with different rotor polarities are systematically compared in order to form the basis for a set of generalized design rules. [ABSTRACT FROM AUTHOR]

A fast finite element (FE) based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines is presented in this paper. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions that exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor $s_f$ for all the design variations, the maximum $s_f$ in the developed method is determined based on the individual slot structure/dimensions and strand wire specifications. Furthermore, in lieu of detailed modeling of the conductor strands in the initial FE model, which significantly adds to the complexity of the problem, an alternative rectangular coil modeling subject to a subsequent flux mapping technique for determination of the impinging flux on each individual strand is pursued. Rather than pursuing the precise estimation of ac conductor losses, the research focus of this paper is placed on the development of a computationally efficient technique for the derivation of strand eddy current losses applicable in design optimization, especially where both the electromagnetic and thermal machine behavior are accounted for. A fractional-slot concentrated winding permanent magnet synchronous machine is used for the purpose of this study due to the higher slot leakage flux and slot opening fringing flux of such machines, which are the major contributors to strand eddy current losses in the windings. The analysis is supplemented with an investigation on the influence of the electrical loading on ac winding loss effects for this machine design, a subject that has received less attention in the literature. Experimental ac loss measurements on a 12-slot 10-pole stator assembly will be discussed to verify the existing trends in the simulation results. [ABSTRACT FROM AUTHOR]

Switched reluctance (SR) machines are attractive because they present relatively high efficiency and torque density in spite of lacking permanent magnets. This paper focuses on a two-objective optimization of an external rotor SR motor with a stator that has concentrated coils and a rotor with magnetically isolated modules. The objectives are minimum loss and mass, and 11 independent dimensionless geometric variables are considered as inputs that affect them. A combined design of experiments (DOE) and differential evolution (DE) approach is proposed. The DOE methodology is used to reduce the search space by eliminating from consideration input variable values, leading to poor-performing designs. Following this initial DOE study, an optimization study based on DE is run over the reduced search space, which leads to significant savings in computation time. Furthermore, a directed graph-based method for comparing different designs on the Pareto front to rank the best compromise designs is proposed. [ABSTRACT FROM AUTHOR]

Axial flux permanent magnet (AFPM) motors are suitable options for solar-powered vehicles due to their compact structure and high torque density. Furthermore, certain types of AFPM machines may be configured without stator cores, which eliminates associated losses and cogging torque and simplifies the manufacturing and assembly. This paper examines two machine designs for use in the solar-powered vehicle of the challenger class—a single rotor, single stator conventional AFPM machine, and a coreless AFPM machine with multiple stator and rotor disks. The response surface methodology (RSM) is utilized for the systematic comparison of the conventional and coreless topologies and to select the optimum designs among several hundreds of candidates. Designs with minimum losses and mass producing required torque with larger air-gap are favored. The performance of the selected designs has been studied via three-dimensional finite element analysis (FEA). The FEA parametric modeling methodology is validated by measurements on three AFPM machines of the conventional and coreless type. [ABSTRACT FROM AUTHOR]

A large-scale finite element model-based design optimization algorithm is developed for improving the drive-cycle efficiency of permanent magnet (PM) synchronous machines with wide operating ranges such as those used in traction propulsion motors. The load operating cycle is efficiently modeled by using a systematic k-means clustering method to identify the operating points representing the high-energy-throughput zones in the torque–speed plane. The machine performance is evaluated over these cyclic representative points using a recently introduced computationally efficient finite element analysis, which is upgraded to include both constant torque and field-weakening operations in the evaluation of the machine performance metrics. In contrast with the common practice, which aims at enhancing the rated performance, the entire range of operation is considered in the present design optimization method. Practical operational constraints imposed by the voltage and current limits of the motor-drive system, excessive PM demagnetization, and torque ripple are accounted for during the optimization process. The convergence to the optimal design solutions is expedited by utilizing a new stochastic optimizer. The developed design algorithm is applicable to any configuration of sinewave-drive PM and synchronous reluctance motors over any conceivable load profile. Its effectiveness is demonstrated by optimizing the well-established benchmark design represented by the Toyota Prius Gen. 2 interior PM motor configuration over a compound operating cycle consisting of common U.S. driving schedules. Multiphysics electromagnetic, thermal, and mechanical performance of the optimized design solutions is discussed in a postdesign optimization stage. [ABSTRACT FROM PUBLISHER]

Permanent-magnet synchronous machines are a high-efficiency motion solution. As the efficiency bar is raised, it is no longer adequate to consider only the dominant core, dc conduction, and friction losses. The challenge for motor developers experiencing additional losses is determining which of the previously neglected losses is significant for their motor. This research presents a best-fit least-squares approach to loss separation that can be applied to experimental data to highlight the source of additional losses. This is a powerful tool for practical motor designers looking to meet challenging specifications. The proposed technique has been applied to the experimental data from three different prototype motors. Although a simple core model of core loss is used, in each case the losses were classified with a residual of less than 2%. Each loss type (defined by proportionality to speed and current) showed good agreement with the corresponding loss type calculated from finite-element analysis (FEA). [ABSTRACT FROM AUTHOR]

A new technique for coupling the electromagnetic, thermal, and airflow analysis is proposed particularly for electric machines that exhibit reduced dependence of core losses with temperature and load and have low rotor losses. Within the overall iterative loop, another inner loop that cycles only the thermal calculations and employs a simplified model to estimate losses is introduced. The thermal and airflow analysis models the conduction, radiation, and convection heat transfer and is based on equivalent circuit networks. A computationally efficient finite-element (FE) technique is employed for the electromagnetic field analysis. The combination of algorithms results in ultrafast processing as the number of outer loop iterations, which include electromagnetic FE analysis, is minimized. The overall computational time is significantly reduced in comparison with the conventional method, such that the new technique is highly suitable for large-scale optimization studies. Example simulation studies and measurements from an integral horsepower interior permanent-magnet motor are included to support validation. [ABSTRACT FROM PUBLISHER]

The proposed hybrid method combines computationally efficient finite-element analysis (CE-FEA) with a new analytical formulation for eddy-current losses in the permanent magnets (PMs) of sine-wave current-regulated brushless synchronous motors. The CE-FEA only employs a reduced set of magnetostatic solutions yielding substantial reductions in the computational time, as compared with the conventional FEA. The 3-D end effects and the effect of pulsewidth-modulation switching harmonics are incorporated in the analytical calculations. The algorithms are applied to two fractional-slot concentrated-winding interior PM motors with different circumferential and axial PM block segmentation arrangements. The method is validated against 2-D and 3-D time-stepping FEA. [ABSTRACT FROM PUBLISHER]