Investigation of ramped air arcs near current zero in dual-flow nozzle system

Ramped air arcs with a dI/dt= 6 A/ mu s were investigated in dual-flow nozzle system. The nozzle pressure ratio was varied to study the arc under different flow Mach number gradients. The dI/dt, dV/dt, and postzero resistance and current measurements were taken for an electrode separation of 5.5 cm and a nozzle gap spacing of 1.23 cm. The adverse shock wave effects were quantitatively observed for nozzle pressure ratios with separated flow in the nozzle. The arc power, which is equal to the total radiation losses and heat transferred from the plasma, was determined near current zero for subsonic and supersonic flow fields. It was shown that the nozzle pressure ratio is a very important parameter in the circuit breaker performance. A comparison of this work with Brown Boveri data was made. It was concluded that the convection stabilized ramped arcs near current zero are laminar and become unstable in the dielectric regime.<
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