The Journal of Engineering (Jun 2019)
Ultra-fast moving coil actuator for power switches in medium-voltage grids
Abstract
The need for faster power switches leads to the following question: Which technical actuation principle has the highest acceleration potential? This study describes the investigation of electrodynamic moving coil (voice coil) actuators. This principle promises no delay for the excitation field because of permanent magnets and a very small electrical time constant of the moving coil. The aim is to find out the limits of the switching time under practicable conditions. In the study, technical limitations of the actuation principle concerning the dynamic behaviour are shown by an analytical approach. It contains the major parameters like stroke or material of the iron poles, the coil, and the permanent magnets. Furthermore, the study discusses thermal aspects and approaches for the mechanical force multiplying by cascaded arrangements. A magnetically optimised elementary unit can be combined parallel or in series. The mechanical load inertial can be divided into a sufficient number of cascaded actuation units. Consequently, only the inherent moving mass determines the acceleration capability. This optimisation was done analytically with the Lorentz force formula and with finite element method simulations. This article describes both approaches, their results, and the experimental verification. The experimental actuator reaches a switching time of 2.7 ms.
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