Evaluation of Sensorless Methods for Synchronous-Linear-Motors by using a Magnetic Equivalent Circuit based Model

Abstract

The Magnetic Equivalent Circuit (MEC) method is investigated for modeling the synchronous-linear-motor characteristics used by sensorless methods. The characteristics of interest are the magnetic saliencies due to the saturation that the secondary flux produces in the primary, and saliencies modification due to the load. They are not represented in the standard Fundamental-Wave model, and the usual tool for analyzing them is the Finite Element Analysis (FEA). Nevertheless, as the FEA models require extremely high computation time for dynamic simulations, the use of MEC is proposed to be used in this paper. The MEC is derived from the motor geometry, magnetic characteristics of the involved materials, and the winding arrangement. Consequently, with this model, a sensorless method can be analyzed and simulated for a given motor design before its prototype is build. In order to test the model, the injection of a high-frequency alternating voltage, as used in some sensorless methods, is simulated with the proposed model as well as implemented experimentally. The obtained results show agreement between them, demonstrating that the model is viable for analysis of sensorless methods.