Field Oriented Control Reaserch Of Linear Induction Motor Considering End Effects

Linear induction motors(LIM) has many advantages such as simple structure, easy maintenance, less environmental pollution and direct drive without the translation mechanisms etc. Therefore, LIM has been widely used in the areas of transportation, military, aerospace and so on. However,LIM has a disadvantage of low efficiency which not only to be improved by modifmg the motor desgin, but also to be improved by applying the appropriate control strategy. We can obtain excellent speed characteristics and fine dynamic response performances as DC motors by using Field oriented control which has gradually become the first option for rotary motors. It is also the right selection for LIM.so the reaserch of Field oriented control has become more and more indispensable.The fundamental difference between a rotary motor and a LIM is the the open airgap which affects the transverse and longitudinal magnetic fields and causes an initiation of the so-called end effects in LIM. In all of these end effects, which include transverse edge effects and longitudinal end effects, the influence of second longitudinal end effect is most of important.The equivalent circuit of rotary motors whose parameters are treat as constants is also suitable for LIM when not considering the end effects. However,the parameters are variable depending on operation speed ,so it is not directly applicable to the LIM as the existence of end effects. Most of existing models are obtained from electromagnetic theory, Fourier transform method or space harmonic method which cann't be directly used for Field oriented control. In this paper, an analysis of LIM using finite element method (FEM) is presented and an equivalent circuit of LIM considering the second longitudinal end effect is developed, using the rotary-motor model as a basis.Field oriented control scheme aligned with the secondary flux based on new equivalent circuit and the control method of rotary motor is shown.The Field oriented control scheme was simulated with and without end effects.Finally, the results not only show the infection of the end effects but also show the validity of the control strategy.