Influence of saliency ratio (xd-xq) on the performance of three-phase synchronous reluctance generators.

Thesis Abstract

In the study of the influence of saliency ratio (Lı/Lı) on the performance of a synchronous reluctance generator (SRG), this project investigates two typical generator rotor designs Generator with cage and without cage otherwise known as cage and cageless rotor respectively. A special attention had been paid to the possible rotor geometries of synchronous reluctance machine, SRM. This ratio can directly influence our insight into the machine’s potential abilities. From the studies of three phase SRG, a modeled direct and quadrature axes equations for both rotor configurations are presented for dynamic simulation. Basic parameters and generator performance, such as phase voltage and current build-up, output power with load current, peak voltage with load current, reactive power with load current are compared for both rotor designs. These analyses from the simulation were carried out by Embedded MATLAB Function. It was observed from capacitor selection that the capacitors ranging from 50 to 120µF produced a suitable voltage build-up in every case without exceeding the current-carrying capacity of the winding coil. Another observation from the result is that, cage-less-rotor can only be excited with much lower capacitor values, between 40 and 65µF. This indicates that cage-less-rotor produces a lower voltage, lower load current and yields lower output powrer. The saliency ratio obtained under rotor geometry modifications does not surpass 7, while the longitudinal magnetization reactance, Xı ı is reduced by at least 20% with respect to value for uniform air-gap. Different values of saliency ratios were investigated through MATLAB simulation by dividing the measured quadrature axis magnetizing reactance, Xı ı with arithmetic progressing numbers ranging from 2, 2.5, 3, 3.5 to 6.5 which mathematically increases the direct axis magnetizing reactance value, Xı ı of saliency ratios by 2Xı ı, 2. 5Xı ı, 3Xı ı, 3.5Xı ı, to 6.5Xı ı. The higher the saliency ratio, the higher the power factor and output power. The saliency ratio is the most importance parameter of a synchronous reluctance generator which is directly proportionally to power factor and output power.