A Novel Analytical Equivalent Circuit for Single-Sided Linear Induction Motors Considering Secondary Leakage Reactance

Single-sided linear induction motors usually appear in magnetic levitation systems of transportation. Since the beginning of such developments, edge effects represent one of the great challenges to overcome in analytical modelling. For almost four decades, in order to simplify the mathematical treatment of border effects, most analytical models have not considered the secondary leakage flux properly. Although concise and accurate in most cases, such approaches have deficiencies in slotted secondaries. This paper presents an analytical equivalent circuit that considers the secondary reactance for both edge effects, i.e., entry and exit sides. The proposed approach uses an analogical RLC circuit which describes the behavior of magnetizing (exit) and demagnetizing (entry) waves, as well as adapted correction factors for transverse effects. By means of an 8 pole/120-175 N prototype, the measured thrust and vertical forces remarkably validate the model for frequencies equal or higher than 60 Hz. The relevance of secondary reactance in such cases can be explained by accounting its influence, specially, in the rise of the demagnetizing entry wave.