Research On High-capacity Squirrel-cage Rotor Induction Generator

Wind is a kind of clean renewable energy, which has developed rapidly for power generation as a general way to utilize the clean energy around the whole world. In the system of wind power generation, the induction machine generates electricity with a squirrel-cage rotor which is driven by a gear case connected to the fan blades. The generated power is combined to the grid via a full-power inverter. So the wind-driven generator plays a leading role as the primary component. This paper is supported by the national defense research project, aiming at researching a1.5MW induction generator with a squirrel-cage rotor for a higher operating stability and a lower cost.In order to satisfy the rated demands and technical requirements of induction generator with a squirrel-cage rotor, the main dimensions can be calculated by analogism of physical quantities. And the initial dimensions of each part of the machine are put forward considering the starting ability, heating load, insulation standards, and so on. Then the air-gap magnetic flux density is going to be calculated with distributed magnetic circuit method given the blocking magnetic paths and the numerical relation of each part. Consequently, the magnetic flux densities of all parts in generator can be deduced, which is the basement for optimization of dimensions.Based on the optimized motor, the resistance and reactance of the machine can be calculated. And the no-load self-excitation capacitor for constant generator terminal voltage as well as the equivalent capacitor at rated load will also be derived. The self-excitation capacitor as the most important external parameter is analyzed with some rewarding solutions about its affects on performance of generators and the method for selecting proper capacitance summarized.Depending on the analysis of induction generators, the whole design procedure is calculated with MATLAB, which helps to determine the final optimization version with some optimizing standard. The curve of power characteristic is then studied. Finally, the temperature of the induction generator with a squirrel-cage rotor is examined compared to the result of coupling calculation of temperature field and fluid field with finite volume method, which is pretty close to the real temperature rise when the machine is operating. The rationality of machine design can be confirmed on the aspect of insulation temperature.