Thesis submitted in fulfilment of the requirements for the degree MAGISTER TECHNOLOGIAE: Mechanical Engineering in the FACULTY OF ENGINEERING at the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY, 2012 / The amount of power a horizontal axis wind turbine (HAWT) can produce is determined by two main factors, wind velocity and rotor swept area. Theory dictates that the power production of a horizontal wind turbine is related to the cube of wind velocity and the square of the turbine diameter (or radius). The power produced at any given time is thus dependent on of the wind velocity and the rotor swept area of the turbine. Wind is variable in availability and consistency. Very little can be done to effect the wind velocity passing through the turbine rotor area and its effect is minimal. Thus understandably if more power is required, from the same wind velocity, the rotor diameter must be increased. A variable length blade can adapt lengthwise to accommodate low wind velocities and similarly high wind velocities during extreme conditions, thus increasing the operational time and power production of the turbine. The work undertaken in this thesis is a comparative study between standard design, fixed length blades to that of a modified design, variable length blade. The project entailed the design and development of small diameter HAWT blades and experimental testing. The turbine blades were designed using applicable theory and manufactured from available materials. For the experiments, the turbine was mounted on a vehicle and driven at various speeds. Due to size limitations, no dynamic adaption was done during testing. The variable length design blade was obtained by cutting increments off. The results obtained from each test were compared at corresponding points and conditions. Final interpretation of results lead to the conclusion that by increasing or decreasing the turbine blade length the area of turbine energy capture can be adjusted to affect the amount of power produced. Additional benefits included, force reduction during extreme operating conditions, extended production period for the turbine and a mechanical start up method during low wind speeds. The financial feasibility did not form part of the scope of this thesis and the technical feasibility of the concept can be thoroughly addressed in future research.

Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The focus of this thesis is on the optimal design, control and evaluation of 3-phase permanent magnet radial flux synchronous machines with non-overlapping, concentrated-coil, double layer stator windings for EV hub drive applications. A simple analytical method is developed that can be used as a first design tool. The method uses and predicts the MMF harmonic content for a certain pole-slot combination as well as the harmonic content for the air gap permeance function. These harmonics are then used to calculate the torque and torque ripple of machines with large stator slot openings and surface mounted permanent magnets. A different approach to calculate the iron, stator copper eddy current and magnet losses is presented. This method specifically looks at the machine during field weakening operation when the flux paths are changing in the machine. Flux density information throughout the machine is extracted from a series of static FE solutions, to calculate the losses and to combine this with an empirical formula. Some machine topology choices are compared for use as hub drives in small electric ve- hicles. The parameters that influence the machine design are discussed and evaluated after a multidimensional design optimization is done and an efficient control algorithm is imple- mented. The algorithm works through the entire operating speed range and make use of, automatically generated, 2D look up tables to determine the correct current reference. A stator lamination design is proposed, that combines the use of rectangular preformed coils and semi-closed stator slots. Two prototype machines, one with a good winding factor and the other with a low winding factor, are built and compared. The manufacturing and testing of the two prototype machines are described and shown in detail. / AFRIKAANSE OPSOMMING: Die fokus van hierdie tesis is op die optimale ontwerp, beheer en evaluasie van 3-fase per- manent magneet radiale vloed sinchroon masjiene met nie-oorvleuelende, gekonsentreerde, dubbel laag stator wikkelinge vir EV hub motor toepassings. ’n Eenvoudige analitiese metode is ontwikkel wat as ’n eerste ontwerp gereedskap stuk gebruik kan word. Die metode gebruik en voorspel die MMF se frekwensie inhoud vir ’n sekere pool-gleuf kombinasie sowel as die frekwensie inhoud vir die lug spleet permeansie funksie. Hierdie frekwensie inhoud word dan gebruik om die draaimoment en draaimoment riffel van masjiene met groot stator gleuf openinge en oppervlak magnete te voorspel. ’n Ander benadering om yster, stator koper werwel stroom en magneet verliese te bepaal word voorgestel. Hierdie metode kyk spesifiek na masjiene onder veld verswakking beheer wanneer die vloed paaie verander vanaf die normale. Die vloeddigtheid, regdeur die masjien, word verkry deur om van ’n reeks statiese eindige element oplossings gebruik te maak en dit te kombineer met ’n empiriese verliesberekening. Die parameters wat die masjienontwerp beïnvloed, word bespreek en geëvalueer na ’n mul- tidimensionele ontwerp optimering gedoen is en ’n effektiewe beheer algoritme geïmplimen- teer is. Die algoritme werk vir enige spoed en is gebaseer op die outomaties gegenereerde 2D opsoek tabelle wat die korrekte stroomverwysing gee. ’n Stator laminasie ontwerp word voorgestel wat die gebruik van vooraf vervaardigde spoele en gedeeltelik toe stator gleuwe moontlik maak. Twee prototipe masjiene, een met ’n goeie windingsfaktor en een met ’n swakker windingsfaktor is gebou en vergelyk. Die ver- vaardiging en toetsing van die twee prototipe masjiene word in detail beskryf en gewys.