Based on the electro-technology theory,this study defines the ratio of maximum torque Tm to starting torque Tst as the starting modulusλst,and reaches a conclusion that X20 can be calculated by using the rotor phase resistance r2 and the starting modulus A,,.

A maximum-torque slip frequency control method is proposed to meet the requirements of mining locomotives and remedys the weaknesses of traditional slip fre quency control such as the PI parameters are hard to determine,the current-slip curve is hard to realize by MCU and the maximum torque can not be obtained.

The circular graph which comes from circular theory and motor equivalent diagram,shows running characteristic clearly and to determine motor parameter via geometric relations:such as losses,efficiency, maximum torque and so on.

This paper studies how to improve the breakdown torque of a.

In this paper, the factors that can influence starting torque, starting current, breakdown torque and min.

Effects of the variation of main parameters of the spheri-cal motor on the electromagnetic torque were analyzeda,nd the variation rules of the maximum static torque(MST)of the motor with the length of stator polest,he radius of the stator iron core,PM content coefficienta,mpere turns of windings and the air gap length were obtained respectively.