Minimum Arcing Interrupting Capability and Opening Velocity of Vacuum Interrupters: An Impact of Magnetic Field

Abstract

Controlled switching technology operates circuit breakers at minimum arcing time for short-circuit current interruption. However, there is no report to reveal an impact of magnetic field on minimum arcing interrupting capability under various opening velocity. The objective of this paper is to determine the impact of magnetic field on minimum arcing interrupting capability under various opening velocities. Three types of contacts were investigated, which were butt-type contact, cup-type axial magnetic field (AMF) contact and spiral-type transverse magnetic field (TMF) contact, respectively. The diameters of all the contacts were 58 mm and the contact materials were CuCr50 (50% of Cr). The vacuum interrupters (VIs) were driven by an electromagnetic repulsion mechanism, whose average opening velocities ranged from 2.6 to 6.0 m/s. The short circuit interruption tests had a current of 31.5 kA (RMS) with a TRV peak value of 73 kV. Experiment results show that the minimum arcing time of butt-type contact and cup-type AMF contact decreases while the average opening velocity increases and it keeps a constant when the average opening velocity reaches a critical value. However, the minimum arcing time of spiral-type TMF contact has been decreasing without the critical value. Meanwhile, spiral-type TMF contact achieve a shorter minimum arcing time compared to the butt-type contact and cup-type AMF contact when the average opening velocity is lower than 4 m/s.