A Direct Control Scheme to Achieve Maximum Acceleration in Linear Induction Motors

Linear induction machines (LIM) have shown their advantages in high speed propulsion in a variety of industries, such as, military, transportation, and aerospace to name a few. Usage of vector control to achieve maximum speed acceleration/deceleration for linear induction machines has been a focal area of research for the past decade. However, due to the trailing eddy current effects and magnetic asymmetry effects, vector control does not provide nearly the functionality for LIM as it does for rotary induction machines (RIM). Therefore, searching for an adequate control scheme with ease in implementation and low cost is the motivation for this paper. Using finite element analysis (FEA) the relationship between traction force and different ranges of linear speed and excitation frequencies in motoring, generating, and electromagnetic braking regions has been explored. By storing these characteristics in the form of lookup tables which provides excitation frequencies resulting in maximum accelerating and decelerating forces, a closed-loop speed control scheme with fast response has been proposed.