Study on Protection Circuits for Micro-Switches in Inductive Load Control System

Micro-switches are used to control the coil of electromagnetic switches, which can control the renewable and sustainable energy distribution systems. Arc ignition of contacts is the way to dissipate energy which stored in coil inductance, so that the arc duration and erosion on contacts of micro-switches exceed expectations. Based on this, it is common to use the parallel capacitance and resistance at both pins of micro-switch as protections. In this paper, arc voltage waveform and images of a micro-switch with resistance-capacitance (R-C) protection circuit are measured. The inductance is 1.25H and the range of voltage is from 50V to 150V, and principles of the protection circuit on arc characteristics are clarified. In addition, we reveal the influence of resistance and capacitance on the protection circuit according to results. The optimal resistance and capacitance suitable for micro-switch is put forward, and protection advantages are verified by test.