The Hybrid Suspension System for Middle-to-Low-Speed Maglev Trains Considering the Prevention of Firm Absorption

The electromagnetic suspension system (EMSS) plays a critical role in providing attractive force for middle-to-low-speed maglev trains, which contains two critical components—an electromagnet and a steel track. However, with the acceleration of trains, the eddy current generated by the relative motion between the electromagnet and the track becomes intensified, which may directly weaken the attractive force. To maintain the suspension air gap between the iron yoke and the track stable, more current needs to be inserted into the winding of the electromagnet. The local thermal surge existing in the winding may appear due to the overloaded input current for long term, which may cause the insulation aging or even damage of the winding. If the short-circuit accident occurs between the neighboring turns of the winding due to the interturn insulating damage of the winding, the loss of suspension force tends to be deteriorated undoubtedly. In this article, a novel hybrid suspension system mixed electromagnetic and permanent magnetic modes is proposed for enhancing suspension force with economical power consumption. However, when applying permanent magnets for assisting electromagnets, the firm absorption (FA) phenomenon needs to be considered. Two suspension schemes with unequal-width and unequal-height iron yokes are launched for reducing FA risk. The corresponding finite element method (FEM) models have been built and verified by experimental results. The comparison of different suspension schemes under the dynamic condition with different relative velocities between the suspension module and the track has been undertaken in the end.