Introduction of DC magnetic suspension to AC magnetic suspension using magnetic resonant coupling

Abstract

DC magnetic suspension operated by transmitted power is introduced to AC magnetic suspension system using magnetic resonant coupling for dynamic stabilization. The target AC magnetic suspension system has a self-stabilization property. Although restoring force is produced without active control in this system, damping is necessary for dynamic stabilization. To generate damping force, a DC magnetic suspension mechanism, which is operated by the power transmitted to the floator through magnetic resonant coupling, is installed in parallel with the AC magnetic suspension mechanism. The newly developed system has a pair of AC electromagnets and another pair of DC electromagnets. The former pair generates positive stiffness according to the self-stabilization property. The latter pair is expected to produce positive damping by shortening the coil of the electromagnet on the stator. However, it is experimentally shown that negative damping is produced because the latter pair also has the self-stabilization property. Therefore, a bias voltage is applied to the DC electromagnet on the stator to make the stiffness negative. As a result, stable suspension is achieved without active control in the developed system. However, the overall stiffness decreases and the stability range is small because the latter pair has negative stiffness. To solve such a problem, a phase-lead compensation is applied to the latter pair instead of the bias voltage. This method can produce positive damping and positive stiffness at the same time so that the suspension characteristics are improved.