Browsing by Author "Botha, Stefan"

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    Three phase rotary transformer for a rotor tied doubly fed induction Machine
    (Stellenbosch : Stellenbosch University, 2022-04) Botha, Stefan; Gule, Nathi; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: With the rising demand for renewable energy sources, wind energy has emerged as a very popular alternative to the use of fossil fuels. The growth in this sec tor has led to an increased emphasis on the reliability of the generating units. The most widely used generator in wind turbines is the doubly fed induction generator (DFIG). Its advantages such as variable speed makes it well suited. The brushless doubly fed induction generator (BDFIG) offers superior reliabil ity due to the replacement of the slip ring assemblies from the standard DFIG. The current employed BDFIG topology results in a more complex machine. In order to retain the simplicity that the DFIG offers, other brushless topologies have to be explored. The rotor-tied, rotary transformer (RT) is one of the proposed alternative topologies. It can be utilized with a standard DFIG and retain the simplicity of the machine. The purpose of this study is to determine the effectiveness of the topology when utilized with a rotor-tied DFIG (RDFIG). The study aims to develop a design methodology that considers the unique layout of the RT, while optimizing the RT for efficiency and minimizing size. An analytical model is used in conjunction with finite element analysis (FEA) to improve on the design while taking into account the non-idealistic nature of the RT. A prototype RT is designed using the proposed analytical model, con structed and practically tested. The resultant efficiency is higher at a smaller size a prototypes built with conventional transformer design. The RT is tested and compares favorably against the FEA and analytical models. It is able to exceed its design rating for short periods but cooling is a limiting factor. The proposed RT is then tested rotor-tied to a RDFIG, and the RT enables the RDFIG to operate without a slip ring and brush assembly. The proposed RT-RDFIG was able to maintain high levels of efficiency and proves that the solution could be viable.