Investigation of vacuum circuit breakers for high currents

The aim of the investigation is to determine the axial magnetic field (AMF), required to keep vacuum arcs up to 100 kA top value in the diffuse mode. The magnetic field is generated by the main current flowing through coils around the vacuum interrupter (VI). The arc was observed with a digital camera in order to relate arc constriction and arc voltage. The 100 kA/sub peak/ arc could be kept diffuse at 5.5 mT/kA. Next, the influence of contact speed was investigated. The dependence of interruptible current on pressure and transient recovery voltage (TRV) was determined.