Winding Function Theory Based Thrust Calculation on Nested-loop Secondary Linear Machine Adapted to Linear Metro

With advantages of strong drive capability, nested-loop secondary linear machine (NLS-LM) has great potentiality in linear metro. For its secondary structure with multiple loops, it is difficult to calculate the electromagnetic thrust of NLS-LM reasonably. Hence, in this paper, one thrust calculation method is proposed considering variable loop inductance and transient loop current. Firstly, to establish the secondary winding function, the modeling domain is confined to a limited range, and the equivalent loop span is employed by analyzing the coupling relationship between primary and secondary. Then, in order to obtain the secondary flux density, the transient secondary current is solved based on the loop impedance and induced voltage. Finally, the electromagnetic thrust can be calculated reasonably by the given primary current sheet and the calculated secondary flux density. Comprehensive simulations and experiments have demonstrated the effectiveness of the proposed method.