Diagnostic measurements on rotary arcs in hollow polymeric cylinders

Rotary arcs in hollow polymeric cylinders have been monitored using electrical and optical techniques. The arcs burning within hollow cylinders were driven by electromagnetic forces. The arc voltage, current, dielectric strength below the arc gap, the optical emissions from the chamber were measured along with high-speed photography. The diameters of the hollow cylinders and magnitude of the applied magnetic field were varied. The arc voltage, especially the extinction peak prior to current zero, increased for larger bore cylinders and higher magnetic fields. By comparing the arc voltage waveforms and arc photographs, this was shown to be because the arcs were elongated. Luminosity was detected even after current zero, when polytetrafluoroethylene was in the arc chamber. The extensive experimental results obtained have enabled empirical mathematical expressions to be derived which yield approximate indications of current interruption capabilities under different operating conditions.