Browsing by Author "Tlali, Pushman Micheal"
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- ItemDesign and performance evaluation of a permanent magnet vernier machine For wind turbine generator applications(Stellenbosch : Stellenbosch University, 2019-12) Tlali, Pushman Micheal; Wang, R-J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Wind power conversion has emerged as one of the attractive and rapidly growing renewable energy resources. Research in this field has indicated a crucial need of developing new or improved electrical machine technologies, as they are essential components in this application. Currently, a cascaded arrangement of mechanical gearbox and a medium- or high-speed machine is the common configuration implemented in wind turbine systems. However, to avoid gearbox issues and to improve on the system reliability, there has been a paradigm shift towards the use of direct drive generators (DDGs) with full scale converters. Since the DDGs runs at the low turbine speed, they usually have heavy structure and bulky sizes due to high torque requirements. The past decades have seen a renewed interest in permanent magnet vernier (PMV) machine, which originates from the integration of the magnetic gearing concept with the conventional permanent magnet synchronous machine (PMSM). The inherent magnetic gearing effect of this type of machine enables it to have high torque density, potential for lighter weight and more compactness than conventional PMSMs, while maintaining the similar structural simplicity. Consequently, it appears to be a suitable candidate for low-speed and/or high-torque applications such as wind turbine DDGs. Despite the above mentioned advantages, the PMV machines are notably characterized by lower power factor that may increase the converter rating requirement and subsequently the system cost. The aim of this research is to develop and evaluate the PMV machine technology for use in the wind power conversion systems. The basic research methodology employed is to first derive fundamental analytical equations that describe the unique performance characteristics of PMV machines, and then to establish a dedicated finite element method based design optimization environment for the design and analysis of PMV machines. In order to show the merits and demerits of PMV machines, a detailed comparison between an optimally designed PMV machine and a conventional PMSM of the same power rating will also be conducted. To validate the performance and design methodology used, an optimally designed prototype PMV machine is constructed, experimentally tested and compared with an existing PMSM machine. In addition, the feasibility of using PMV machine technology for large wind power applications (3MW) is also evaluated in terms of performance, costs, size and weight. The outcome from this work outlines the advantages and disadvantages of the PMV machine technology and provide insight on the potential of this technology for MW scale wind power applications.
- ItemDesign and performance evaluation of an outer stator magnetically geared permanent magnet machine(Stellenbosch : Stellenbosch University, 2015-03) Tlali, Pushman Micheal; Wang, R-J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: Please refer to full text for abstract.