Reseach On The Electromagnetic Characteristics And Losses Of A Variable Speed Operating Doubly Salient Generator

The doubly salient electro-magnetic generator, resembling the simple structure of an SR generator, offers the merits of low cost and high efficiency. With the usage of independent field winding located in the stator slot, the output voltage and power can be easily regulated. Also, the flexible way of excitation guarantees the stability of output power and voltage under the variable speed and variable load condition. Thus, it exhibits great value and prospect in the stand-alone power systems.This thesis summarizes the recent development and features of variable-speed generating system, core component of the stand-alone power system. The author elaborates the key requirements for the generator applied in the variable-speed operating system as well as summarizing the situation and problems of current generators. This paper systematically summarizes the recent development of proposed doubly salient electro-magnetic generator which demonstrates a good future in the variable-speed generating system.This paper proposes the schematic diagram of the variable-speed operating doubly salient brushless dc power system. The author systematically summarizes operation mechanism of proposed variable-speed operating doubly salient generator. Comparison and analysis are made on the impact of different independent parameters with regard to output performance. Sensitivity analysis of the laminated structure parameters in terms of power is also conducted. Comparative analysis is made between the 18/12-pole and 12/8-pole doubly salient electro-magnetic generator in terms of inductance characteristics, load characteristics, regulation characteristics under variable speed operation.Formula for electromagnetic losses of doubly salient electro-magnetic generator is derived in order to analyze the relationship between the loss balance and geometric parameters. The stator yoke coefficient is defined. The relationship between the defined stator yoke coefficient and the loss balance, current density, output power and efficiency, effective material consumption and ratio between stator iron and copper consumption is discussed. A 3-D thermal FE model has been built based on the optimized dimensions and calculated electrical loss in previous analysis. The thermal performance of the proposed doubly salient electro-magnetic generator is predicted to ensure the maximum temperature rise in a safe range. The impact of current density on the thermal performance is studied as well.Finally, a totally enclosed self-cooling prototype doubly salient electro-magnetic generator has been developed and tested. The experimental data confirm the validity of previous theory and analysis. Experimental results reveal that the proposed doubly salient electro-magnetic generator can provide a stable and efficient performance for stand-alone power system.