Observations on switching characteristics of arc chutes in DC contactors

A steady rise of voltages and currents in direct current (dc) applications challenges the limits of available dc switchgear. Today many of the existing dc contactors are based on slightly modified ac devices. Customers and manufacturers feel uneasy about new concepts for switchgear and are lacking information about their suitability for specific application areas thus requesting extensive tests of devices under consideration. The paper presents commonly used principles of arc chutes and their arc extinction behavior at and above the rated direct current. Based on tests at the high power lab at Technische Universitaet Ilmenau basic requirements for arc chutes based on ceramics and metal splitter plates are introduced. The relation between size of the arc chute and consequences for arc extinction in different principles is described and compared to ac behavior.