用于单相异步电动机变频器的研究

从理论上论述了单相电容电动机变频调速的可行性，在对称运转的条件下导出了单相电容电动机的电压频率关系式，并给出了相应的电压型逆变器的原理图．应用矢量法分析了该变频器的输出波形，并据此提出了一种新型的脉宽调制（ＰＷＭ）波产生方法．实验结果表明：在指定的频率范围内，单相电机速度可调，运行状态良好．

Study on a New Fuzzy Feedforward Network

A six layer fuzzy feedforward network and its algorithm are proposed to solve the problem in the qualitive testing of concrete structures by the ultrasonic pulse method. A multi factor synthetic evaluation method is adopted in evaluating the quality of concrete and the experience knowledge of the expert is used in directing the training of the network. The experimental results show that the network is effective.