Rong-Jie Wang

Optimal design of a coreless stator axial flux permanent-magnet generator

This paper describes a hybrid method for calculating the performance of a coreless stator axial flux permanent-magnet (AFPM) generator. The method uses a combination of finite-element analysis and theoretical analysis. The method is then incorporated into a multidimensional optimization procedure to optimally design a large power coreless stator AFPM generator. The measured performance of the manufactured prototype compares favorably with the predicted results. The design approach can be applied successfully to optimize the design of the coreless stator AFPM machine.

Analysis and Performance of Axial Flux Permanent-Magnet Machine With Air-Cored Nonoverlapping Concentrated Stator Windings

In this paper, the performance of air-cored (ironless) stator axial flux permanent magnet machines with different types of concentrated-coil nonoverlapping windings is evaluated. The evaluation is based on theoretical analysis and is confirmed by finite-element analysis and measurements. It is shown that concentrated-coil winding machines can have a similar performance as that of normal overlapping winding machines using less copper.

Calculation of eddy current loss in axial field permanent-magnet machine with coreless stator

This paper presents a hybrid method for the calculation of eddy current loss in coreless stator axial field permanent-magnet (AFPM) machines. The method combines the use of two-dimensional finite element (FE) field analysis and the closed-form eddy loss formula. To account for three-dimensional field effects in an AFPM machine, a multilayer and multislice modeling technique has been devised. Experimental tests are carried out to validate the method. It is shown that the proposed method predicts the eddy current losses of a coreless stator AFPM machine with high accuracy.

Development of a thermofluid model for Axial field permanent-magnet Machines

A thermofluid model combining a lumped parameter heat transfer model and an air-flow model of a typical axial-field permanent-magnet (AFPM) machine is developed. The accuracy and consistency of the derived model are assessed by comparing the calculated flow rate and temperature values of a prototype machine with the measured ones. The developed thermofluid model is shown to perform thermal calculations with reasonable accuracy.

Design and Evaluation of a Magnetically Geared PM Machine

This paper presents the design and evaluation of a magnetically geared permanent magnet (PM) machine with an inner stator. A brief overview of relevant operating principles is given first. A simplified design and simulation methodology, which can ensure that the magnetic gear and the stator are well matched, is then devised. The method is applied to the design optimization of a small machine resulting in a design with a maximum torque density of 115 kN · m/m3 per active volume. To validate the design, a working prototype has been built and experimentally evaluated. It shows that this computationally efficient design methodology is well suited for the optimization of magnetically geared PM machines. Finally, a method of analyzing the operating points of the machine is described. Relevant conclusions are drawn and recommendations for future work are given.

Finite-Element Time-Step Simulation of the Switched Reluctance Machine Drive Under Single Pulse Mode Operation

This paper proposes two distinct numerical simulation methods using finite-element time-step analysis for predicting the current waveform of a switched reluctance machine drive and explains them in detail. It evaluates and compares the methods in terms of waveform results and simulation time, with the focus on only single pulse mode operation. The paper also reviews important factors that affect the simulated current waveforms. It presents and compares measured and simulated multi-phase current waveforms of a 49 kW switched reluctance machine drive under single pulse mode operation.

Torque capability comparison of two magnetically geared PM machine topologies

This paper presents a comparison of the torque capability of two PM machines with integrated magnetic gears for low speed, high torque applications. The machines are also compared against a more conventional fractional-slot PM machine to evaluate the benefits of the geared machines. The comparison is based on the optimal torque per active mass that could be achieved within a given volume. The machines are optimized using 2D finite element (FE) analysis and the optimal designs are further evaluated using 3D FE analysis. For the geared machines, an optimization procedure is employed which ensures that the gear and stator parts are well matched.

Formulation, finite-element modeling and winding factors of non-overlap winding permanent magnet machines

The layouts, formulation and winding factors of iron-and air-cored non-overlap winding permanent magnet machines are considered in this paper. The winding formulation gives information about the use of negative periodical boundary conditions in the finite element analysis. Particular attention is given to air-cored non-overlap windings, with entirely different results regarding optimal slot-pole combinations.

Mechanical design considerations of a double stage axial-flux PM machine

This paper evaluates the mechanical design and construction of a 300 kW, double-stage, axial-flux permanent magnet (AFPM) machine. Finite element simulations were used to determine the severity of the attraction force between the rotor discs. The huge attraction force also caused problems during machine assembly, because the closer the discs are brought in, the larger the force. The results obtained from the simulations suggested an increase in yoke thickness in order to withstand the attraction force on it. The simple lumped parameter thermal model was established to evaluate the effectiveness of the air-cooling, which is compared with measurements taken on a prototype AFPM machine.

Two-dimensional Cartesian air-gap element (CAGE) for dynamic finite-element modeling of electrical machines with a flat air gap

This paper extends the air-gap element (AGE) to enable the modeling of flat air gaps. AGE is a macroelement originally proposed by Abdel-Razek et al. (IEEE Trans. Magn., vol. 17, pp. 3250-3252, 1981; ibid., vol. 18, pp. 655-659, 1982) for modeling annular air gaps in electrical machines. The paper presents the theory of the new macroelement and explains its implementation within a time-stepped finite-element (FE) code. It validates the solution produced by the new macroelement by comparing it with that obtained by using an FE mesh with a discretized air gap. It then applies the model to determine the open-circuit electromotive force of an axial-flux permanent-magnet machine and compares the results with measurements.