An influence of an ambient magnetic field induced by a nearby parallel conductor on high-current vacuum arcs

Vacuum arcs are well influenced by a nearby ambient magnetic field. This effect may cause a burn-out of the shield in a vacuum interrupter or even cause a failure interruption. The objective of this paper is to determine an influence of a nearby ambient magnetic field, induced from a conductor parallel assembled to a vacuum interrupter, on the high-current vacuum arc characteristics in the VI. A copper rod conductor is assembled in parallel but electrically connected in series with a test vacuum interrupter. The distance between the conductor rod axis and the test vacuum interrupter axis was controlled as 60 mm, 100 mm and 140 mm, respectively. In the vacuum interrupter, cup type axial magnetic field electrodes were used, which has a contact material CuCr30 and the contact diameter was 42 mm. Contact gap was set to 6mm and 12 mm, respectively, in order to compare an influence of the ambient magnetic field on the high-current vacuum arc behaviors. Arc current is provided by a single-frequency LC discharging circuit, which provides an arcing time of 10.4 ms. And the arc current increased from 3.1 kA to 24.8 kA, which stepped by 3.5 kA. Experimental results showed that with a stronger ambient magnetic field, the arcing energy variation was higher and the arc voltage noise lasted a longer duration. As the ambient magnetic field increased from the minimum case (No copper rod) to the case of axial distance 140 mm, 100 mm and the strongest case 60mm axial distance, the arc energy variation range increased from 0.66 kJ to 1.25 kJ, 1.36 kJ and 1.78 kJ, respectively, at 10.3 kA with the 12 mm contact gap distance. Correspondingly, the arc energy variation range increased from 0.82 kJ to 0.75 kJ, 0.84 kJ and 1.07 kJ at 17.8 kA with the 6mm contact gap distance. And the arc-voltage noise duration increased from 2.6 ms to 4.5 ms at 18.1 kA with the 12 mm contact gap distance, and the duration increased from 2 ms to 3.8 ms at 17.8 kA with the 6mm contact gap distance.