Browsing by Author "Britz, Joseph Juan"
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- ItemOptimisation and dynamic effect of slip couplers in geared wind drivetrains(Stellenbosch : Stellenbosch University, 2019-04) Britz, Joseph Juan; Kamper, J. Maarten; Stellenbosch University. Dept. of Engineering. Dept. Electrical and Electronic Engineering.ENGLISH ABSTRACT: Two electromagnetic (EM) torque couplers, which are referred to as slip couplers, are designed and optimised to be placed in a 2.2 kWwind turbine drivetrain. These slip couplers make the drivetrain more robust, by filtering unwanted torque oscillations. The slip coupler performance is evaluated using EM finite element method (FEM) software, implemented in a Python/Semfem script. The slip coupler is a polyphase electric machine, and a dq inductance estimation method is used to solve for different static rotor steps iteratively. Both slip coupler designs are optimised using genetic and gradient-based algorithms. The NSGA-II and MMFD optimisation algorithms are utilised in the Visualdoc environment, to minimise the total mass of the design. The optimisation constraints and influence of the design variables are evaluated using a colour-graded Pareto and dominated-solution space. One of the slip coupler designs improves upon a similar design found in literature, because the NSGA-II was used together with the MMFD optimisation algorithm. A time-transient analysis of both slip couplers is performed using Ansys Maxwell, and the currents and flux-linkage values compare well with Semfem. The torque ripple values generated by Maxwell casts doubt on some of the results and indicates that another EM-FEM software suite should be used. Finally, the wind turbine is modelled using Matlab Simulink, and the unforced and steady-state response to a wind gust and tower shadow component is determined. A two-mass drivetrain model, with flexible shafts going into and out of the gearbox, is tested. In conclusion, a slip coupler, when placed on the turbine side of the drivetrain, reduces higher-frequency torque vibrations and may be a viable wind turbine component in future designs.