Characteristics Analysis and Dynamic Test of Air-Cored Permanent Magnet Linear Synchronous Motor for Null-Flux PMEDS Vehicle

The potential of the null-flux permanent magnet electrodynamic suspension (PMEDS) has been delivered in terms of levitation and guidance. However, exploration of the propulsion system remains ambiguous, especially in analytical models and dynamic tests. In this work, the electromagnetic characteristics of air-cored permanent magnet linear synchronous motors (PMLSMs) are investigated, and a physical prototype equipped with complete measurement instruments is established and measured for the first time. First, the structure and principle are introduced, followed by the tenable analytical model of air-cored PMLSM using the virtual displacement method. In addition, the dependence of the exciting current, lateral gap, and vertical offset on three-axis electromagnetic forces under two power angles is investigated through simulation and mathematical calculations. Finally, the complete measurement system, including the positioning and speed system, a three-axis accelerometer, and auxiliaries, is constructed, along with the real-scale magnets. Linear dynamic tests are performed on the physical prototype, measuring and analyzing speed, displacement, and acceleration under varying exciting currents and vertical offsets. Results show that the analytical model enables fast and accurate calculations. In practical applications, the propulsion force decreases with vertical offset. Compared to the current, the vertical offset possesses less contribution share of influencing propulsion performance. This work provides valuable insights for optimization design, coupled modeling and dynamic analysis, and test conditions of null-flux electrodynamic suspension vehicles.