Study of arc velocity in an arc-rotating gap based on B-dot probes

Switch is one of the most important parts of the pulsed power technology. An arc-rotating switch controlled by axial magnetic field is designed and built to meet the needs of high voltage, high current, large charge transfers, slight electrode erosion and long lifetime. The electrodes are coaxial cylinder configuration and the shape was optimized to make the electric field well-distributed. So the arc starts dispersedly in uniform electric field. The coils which connected to the inner electrode are placed both at the top and bottom of the switch. The resultant magnetic field is in axial direction and mirror configuration. This makes the rotating arc moving to the middle of the electrode no matter wherever it starts and avoiding damage to the insulator of the switchbody. B-dot probes are adopted to measure the arc velocity. The current is trapezoid-like waveform and generated by a time-sequence discharge power supply. The current is in the range of 17-72 kA and magnetic induction values of 0.104-0.628T. The arc velocity in different magnitude of magnetic flux density is obtained by changing the number of turns of the coils. And the results are compared to other arc-rotating switches. The relationship between average arc velocity and the current and magnetic field is obtained by fitting the experimental data. The equation is compared with other published result, and this research extends the data of arc velocity to high current range.