Anode Surface Temperature Determination in High-Current Vacuum Arcs by Different Methods

The electrode surface temperatures of Cu-Cr butt electrodes exposed to vacuum arcs with sinusoidal currents of 10-20 kA and under external axial magnetic field were determined. Different experimental techniques were applied that can be distinguished by the used spectral wavelength range, their temporal, and spatial resolution. Near infrared spectroscopy was carried out by means of a fiber optic spectrometer working in the wavelength range from 900 to 1670 nm with a temporal resolution of 1-2 ms. Electrode surface temperatures after current zero were obtained from the relative shape of the spectrum using the Planck curve fitting procedure. Furthermore, electrode emissivities were derived after performing absolute calibration of the spectra. Pyrometric measurements were performed in the spectral range around 2 μm with high temporal but without spatial resolution. 2-D distributions of the electrode temperature were obtained from high-speed video thermography using a camera with a metal interference filter at 890 nm.