一、前言三相感应电动机由于价格低廉和结构坚固等优点,很早就被采用作为超重机的驱动部件。但是对于位能负载,它难于取得同步转速以下的低速,因此如何获得下降时的低速,在起重机的实际应用中是个重要课题。日本在过 First, the foreword Three-phase induction motor due to low prices and strong structure advantages, has long been used as a drive component of overweight machine. But for the bit load, it is difficult to obtain the low speed below the synchronous speed. Therefore, how to obtain the low speed during the drop is an important issue in the practical application of the crane. Japan is over