1.引言在过去的六十年,随着客货运量的增长,运输时间的缩短(?)无论是地方短途还是长途铁路运输都要求牵引车辆具有更高的驱动功率。然而,可用于安置牵引电动机的空间不变甚至减小,这就要求必须显著提高电动机单位质量的功率。六十年来,直流和脉流牵引电动机单 1. INTRODUCTION In the past sixty years, with the increase of passenger and freight traffic, the transportation time shortened (?) Both local short-haul and long-haul railways require towing vehicles with higher driving power. However, the space available for placement of the traction motor is unchanged or even reduced, which requires that the power per unit mass of the motor must be significantly increased. For six decades, DC and pulsar traction motors alone