This paper presents a concept in the form of a flow chart for analyzing and designing permanent magnet machine by finite element method (FEM) including rotor motion. According to our flow chart, geometry modeling will automatically be made by script. Therefore, it is easy in changing design parameters. Two programs have been developed based on the proposed flow chart, one for static solution and the other for nonlinear transient solution. The magnetic saturation model and solvers have been discussed. These ensure that the FEM program is convergent and runs faster during high saturation. The influence of slot opening on the magnetic field and internal voltage is investigated. Results are used to select slot opening for maximizing internal voltage.@en

This paper studies distribution of eddy currents and eddy current losses in the rotor of concentrated winding exterior rotor permanent magnet machines in flywheels. The two-dimension nonlinear transient finite element method (FEM) model including rotor motion was used. Influence of slot opening on the eddy current loss in magnets and rotor back iron is investigated. Segmented magnets for reducing the eddy current loss are also surveyed. The proposed approach and results can be used to select the slot opening that minimizes rotor eddy current losses while maximizing the internal voltage. The used method allows monitoring of the eddy current losses in rotor as function of time, rotor speed, operating mode and stator slot opening. It therefore constitutes an indispensable tool in the design of PM machines taking the eddy current losses in the rotor into account.@en

In literature, many different expressions for Carter factor can be found leading to confusion. This paper evaluates Carter factor expressions by comparing finite element computations in order to find the most suitable one which can be used in the design of permanent magnet machines. This paper shows limitations of conventional literature of slotting effect in the range of small slot opening. Finite element analysis based results show that calculation of magnetic saturation correction factor based on tooth flux density brings up results more accurate than that based on air gap flux density. The analytical model is improved by incorporating static FEM. This leads to hybrid model. Correction factors for slot opening, fringing and magnetic saturation are calculated online by static FEM model. In order to implement this concept, a static FEM program was developed. The program is able to make geometry model and handle boundary conditions automatically. To speed up the refinement of design results, a nonlinear transient finite solver based on scripts was also developed. Our implementation ensures that design parameters can be changed easily. Nonlinear finite element computations and experiments are compared. They are in very good agreement, with an error in the internal voltage of only 1.5%. Comparison of the analytical models, the proposed model and transient FEM model shows that the proposed model is more accurate in predicting permanent magnet machine behavior than conventional analytical model.@en

Five promising permanent magnet (PM) machine configurations, namely machine 1 with 24-slot/16-pole, machine 2 with 27-slot/18-pole, machine 3 with 24-slot/20-pole, machine 4 with 24-slot/28-pole and machine 5 with 27-slot/24-pole are compared to find out the best one for a small ship application. A nonlinear two-dimensional finite element analysis including rotor motion is developed for this study. Comparison results show that the machine 4 is the best selection if using criterion of maximum torque density. If the criterion is maximum efficiency, the conventional machine 2 is the best option. However, if using a multi-criteria that compromises between maximum torque density and maximum efficiency, the machine 3 is the best selection.@en

This paper focuses on influence of design parameters of permanent magnet machines with concentrated windings on cogging torque, torque ripple and mean torque. An efficient approach is presented to estimate the magnet width and slot opening width for minimizing cogging torque and/or maximizing mean torque. Two-dimension nonlinear finite element analysis including rotor motion is used for the calculation. The torque is calculated using different methods: Maxwell's stress tensor and Virtual work method. Comparison of results between linear and nonlinear magnetic circuit show that the torque is sensitive with magnetic saturation. The maximum torque of the linear case is about 15% higher than for the magnetic saturation case. Linkage flux, internal voltage and mean electromagnetic torque calculation are verified by experiments with error margin smaller than 1%, 2% and 3% respectively.@en

The machine under study is a surface-mounted outer rotor permanent magnet (PM) synchronous machine with concentrated windings, which is integrated in a flywheel of a diesel engine. The main objective of this work is to build an accurate nonlinear transient finite element method (FEM) model coupling to circuit model and validate this experimentally. The FEM model is made by scripts, so it is very convenient to change design parameters of PM machine. This will help in design optimization of PM machines. A sample PM machine is investigated for validating no-load voltage, load voltage, electric current, electromagnetic torque, short circuit current and reactance of FEM model. Comparison of simulation and experimental results shows very good agreement with error margin smaller than 3%. Results show that the end effects of a PM machine with concentrated windings having large number of teeth and poles can be neglected, even when its diameter is larger than its length. Analysis of results during three-phase short circuit shows that armature current during short circuit is limited strongly by armature reaction in the d-axis direction, even though the winding resistance is much smaller than the reactance. It can be shown that a PM machine designed with reasonable reactance can avoid demagnetization due to three-phase short circuit.@en

This paper presents feasible options for generators in flywheel of diesel engine for small maritime application. An outer rotor permanent magnet (PM) machine with concentrated windings is preferred for this application since it has good integration in a flywheel, higher power density and efficiency than electrically excited synchronous generators, induction generators, etc. A nonlinear transient finite-element-method (FEM) model is developed to calculate iron losses. Afterwards, the model is used for optimal design of a neodymium PM generator improved in terms of power density. Magnet thickness of redesigned generator is only 2 mm, so it has less possibility to break during maintenance. The FEM model is validated by experiment. Results show good agreement.@en