Influence of Magnetic Flex Density on “Magnetic Blow-out” of Direct Current High Voltage Arc

The use of make-and-break DC power supply circuits is rapidly increasing for applications such as solar power generation and electric vehicles (EV). However, within the circuits, it is difficult to extinguish the arc generated when the electrical contact is open. One solution is to use the so-called "magnetic blow-out" method, which relies on the Lorentz force of magnetic flux. A detailed analysis of how the magnetic flux density affects blow-out is an important issue. Toward this, we experimentally investigated the relationship between magnetic flux density and arc duration time. In this experiment, the magnetic flux density was varied in the range of 1.2 to 150 mT, the source voltages used were DC 100, 300, and 500 V, and the current was set at a constant 10 A. The opening speed of the contact was three patterns of 10, 50, and 100 mm/s, and the contact material used was tungsten. Arc duration and arc energy were measured from the voltage /current waveform and power waveform of the arc discharge.The arc duration was found to be almost inversely proportional to the increase in magnetic flux density. Furthermore, the arc duration decreased by 80% or more with a magnetic flux density of 10 mT relative to when there was no magnetic field. The arc at the initial stage was constrained between the electrical contacts. When the gap length, which depended on the magnetic flux density, was reached, the arc discharge rapidly moved to the outside by magnetic blow-out. Therefore, we defined the time during which the arc discharge was restricted as tr. The time at which the arc voltage abruptly increased immediately before the arc extinguishment was defined as the sudden change time ts. Understanding the relationships among magnetic flux density, tr, and ts is essential for clarifying the effective magnetic flux density needed to extinguishing arcs.