A Mathematical Model for Layout Design of Linear Induction Motors

Abstract

The designing of induction motors is considered as a two-stage process of synthesizing an electromechanical system. At the first stage, the device layout is designed, during which the electric motor main dimensions and electromagnetic loads are determined based on empirical data. At the second stage, the device detailed design is developed. The models and methods applied at the stages of layout and detailed designing of rotating and linear induction motors (LIM) differ radically from each other. The following requirements are imposed on the LIM design models. First, the LIM model should allow the designer to calculate the intensity and spatial distribution pattern of the electromagnetic field and secondary current for each speed value. Second, the LIM model should be able not only to link the main dimensions with electromagnetic loads, but also explicitly produce the numerical indicators of electric motor energy efficiency and thermal load. A design model is proposed that satisfies the above-mentioned requirements and describes the LIM electromechanical, energy and thermal states. The model input parameters are the main dimensions and electromagnetic loads of the device. The controlled parameters are the electromagnetic force, efficiency and temperature of the inductor winding. The system layout is designed by evaluating the values of controlled parameters with variations of input parameters in technically feasible ranges. The article presents the results of designing a LIM according to the proposed model with an electromagnetic force of up to 1000 N, motion speed up to 12 m/s, working stroke up to 2.16 m, and efficiency up to 46%. The results of the thermal calculation testify that the electric motor can operate in short-term and intermittent modes. The results of calculating the performance of an electric motor with the same dimensions and a reduced current density in the inductor winding are also presented. An electric motor with insulation class F and natural air cooling develops an electromagnetic force of up to 116 N and can operate continuously over the entire speed range.