Evaluation of passive stability through structural ingenuity for an ac ampere-type magnetic suspension system

This paper describes the successful realization of a fully non-contact magnetic levitation (maglev) system by incorporating the concept of the rotational center (RC) and applying structural modifications to the levitating object in an AC Ampere-type maglev configuration. The proposed AC Ampere-type maglev system is an enhanced version of conventional AC induction-type maglev. In contrast to the conventional one, this system integrates an AC electromagnet (EM1) that induces repulsive forces and additional electromagnets (EM2) that generate Ampere forces. The Ampere force is generated as the cross product of the induced current in the levitating object and the magnetic flux produced by EM2. By appropriately adjusting the phase difference between the induced current and the magnetic flux, it is possible to realize a magnetic levitation system in which the object is suspended beneath a stator composed of multiple electromagnets. The levitating object is an aluminum (Al) ring, referred to as a "squirrel-cage Al ring." To set the RC at a location far below the Al ring, a pair of permanent magnets is used. One of the magnets is connected to the Al ring via three lightweight threads. The relationship among the electromagnetic forces—namely, the alternating repulsive force and Ampere force—generated in the Al ring, the attractive force produced by the pair of permanent magnets, and the gravitational force of the levitating object were experimentally investigated. In the levitation experiment, the object was suspended near the equilibrium point, with a vibration amplitude of approximately 0.1 mm and a magnetic stiffness of 19.1 mN/mm. Thus, with a touch of structural ingenuity—suspending permanent magnets from the squirrel-cage Al ring—we have successfully realized a non-contact, passive, and pendulum-style AC Ampere-type maglev system.