Browsing by Author "Mabhula, Mkhululi"
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- ItemAnalysis and design optimisation of grid-connected wound-rotor synchronous and induction motors(Stellenbosch : Stellenbosch University, 2019-12) Mabhula, Mkhululi; Kamper, M. J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: The dissertation presents new approaches in the analysis, design and optimisation of three-phase cylindrical wound-rotor synchronous (WRSM) and induction (WRIM) motor types. The new approaches are based on the analysis of the steady-state finite element method (FEM) in which the parameters and performances of the motor types are predicted. Absolute optimum designed WRSM and WRIM motor types can at best be obtained by the use of improved parameters and performance calculation methods in the design optimisation process. This dissertation proposes simple, fast and accurate parameter and performance calculation modern approaches for grid-connected WRSM and WRIM motor types using two-axes electromagnetic models. The modern approaches are based on non-classical models in which iterative processes are utilised using static FEM in conjunction with the motor types phasor diagrams. During the iterative processes, the electric circuit and magnetic field equations are coupled to access important parameters of the motor types. The access of parameters using iterative processes solves the excitation currents at different operating points of the motor. The parameters are accurately calculated using a FEM based method of freezing the motor core permeance. The dissertation investigates and expands the use of these parameters as an effective and powerful tool for explaining the motor behaviour under different operating points. A great deal of attention is also given to the design optimisation of the motor types during which a relatively efficient optimisation procedure is shown. In this study, the proposed model approaches are verified by employing a commercial FEM ANSYS-Maxwell and experimental tests in the laboratory. The study also gives the model approach and the design optimisation procedure of a 6 MW slip-ring motor used for milling purposes. In the analysis of this, the skin effects are perfectly fitted in the proposed model approaches The study presents a successful application of the proposed model approaches to the parameters and performance prediction and the design optimisation of the grid-connected WRSM and WRIM motor types. The proposed model approaches demonstrate accuracy, simplicity and fastness which are some of the key aspects in the electrical machine design.
- ItemCross-coupling inductance parameter estimation for more accurate performance evaluation of wound-field flux modulation machines(MDPI, 2020-10-22) Mabhula, Mkhululi; Akuru, Udochukwu B.; Kamper, Maarten J.ENGLISH ABSTRACT: In this paper, a proposed numerical frozen permeability modeling procedure is fully derived to accurately estimate the parameters of two variants of wound-field flux modulation machines (WF-FMMs) namely: wound-field flux switching machine (WF-FSM) and DC-excited vernier reluctance machine (DC-VRM). During the procedure, the contribution of saturation to the variation of the machine parameters is investigated. The parameter variation effects on the machine performance is also investigated. It is shown that analysis of WF-FMMs is better understood by using the proposed procedure which computes accurately the machine parameters.