Transition from slip-frequency control to vector control for induction motor drives of traction applications in Japan

AC motor drive systems for electric rolling stocks with variable-voltage, variable-frequency inverters have many features such as high performance, maintenance free, smaller size and light weight. This paper describes brief history on control methods for induction motor drives of railway traction applications in Japan. That is the transition from the slip-frequency control to the vector control. Furthermore the superiority of the vector control over the slip-frequency control is summarized and is shown with actual data of running trains.