Selected Nature-Inspired Algorithms in Function of PM Synchronous Motor Cogging Torque Minimisation

Both permanent magnet brushless DC motors and permanent magnet synchronous motors have attracted wide attention and are increasingly used in industrial high-performance applications in recent years. Those motors are known for their good electrical, magnetic and performance characteristics, but there is one parameter known as cogging torque that has a negative influence on the performance characteristics of the motor. This pulsating torque is generated as a result of the interaction between the stator teeth and the permanent magnets. The minimisation of the ripple of this torque in those permanent magnet motors is of great importance and is generally achieved by a special motor design which in the design process involves a variety of many geometrical motor parameters. In this research work, a novel approach will be introduced where two different nature-inspired algorithms, such as genetic algorithm (GA) and cuckoo search (CS) algorithm are used as an optimisation tool, in which the defined equation for the maximum value of the cogging torque is applied as an objective function. Therefore, a proper mathematical presentation of the maximum value of the cogging torque for the analysed synchronous motor is developed and implemented in the research work. For a detailed analysis of the three different motor models, the initial motor and the two optimised motor models are modelled and analysed using a finite element method approach. The cogging torque is analytically and numerically calculated and the results for all the models are presented

Study of the performance characteristics of surface permanent magnet motor at various magnetization patterns

Purpose – In the present paper the influence of magnetization patterns of the rotor magnets on the performance characteristics for surface permanent magnet (SPM) motor is investigated. The objective is to show how the electromagnetic and electromechanical characteristics of this type of motor can be significantly changed by applying various magnetization patterns of permanent magnets placed on the rotor surface. Design/methodology/approach – At the beginning a survey of possible and most frequently used magnetization patterns for permanent magnet motors is presented. The research is focussed on the comparison of performance characteristics and is developed into three levels. It is started with a conventional SPM motor having segmented permanent magnets, and two magnetization patterns are considered: parallel and radial. Showing no significant difference of the motor performance at parallel and radial magnetization, for further investigation only radial magnetization, being more conventional, is considered. In the second step, the counterparts of SPM with two Halbach array configurations, under the constraint of fixed magnet volume, are studied. Finally, detailed comparative analyses of SPM at radial, Halbach 1 and Halbach 2 magnet patterns are presented. Advantages and drawbacks for suggested magnet configurations are discussed. Findings – It is presented how the magnetization pattern of the rotor permanent magnets can have a substantial impact on the SPM motor performance characteristics. From the analysis of magnetic field properties at various types of magnetization, it is observed that both shape and rates of the characteristics, for radial magnetization and Halbach 2 configuration, exhibit similar features. It is due to the fact that Halbach 2 array cancels magnetic flux above the permanent magnets, i.e. strengthens the magnetic field in the rotor, and enhances the coupling between the rotor and stator magnetic field. It is worth to emphasise, that due to less saturation of the magnetic core and lower iron loss at Halbach 1 and Halbach 2 magnetization, it is possible to increase armature current and consequently to increase the electromagnetic torque. This fact could be interesting for further research. Originality/value – The paper presents an original comparative analysis for performance characteristics of a surface permanent motor at various magnetization patterns. The novelty of the paper is seen in the introduction of two Halbach magnetization array for permanent magnets and improvement of the performance characteristics for the analysed motor