Experimental setup for quantifying the emission coefficient of contact material for infrared temperature measurement

Different vacuum interrupters (VI) are equipped with Transversal Magnetic Field (TMF) contacts. Due to the current path, a transversal directed Lorentz-force is affecting the electric arc to move in a circular, in order to reduce the heat input and therefore the local erosion of the contact surface. The degree of the contact erosion is dependent on the local temperature of the arc root, which can be measured in a test vessel using a high-speed infrared camera. In order to measure the temperature of a surface by thermography, it is essential to know the emission coefficient of the investigated material. The emission coefficient is a function of view angle of the camera onto the surface. Values of spectral emission coefficients for melting copper at several spectral wavelengths with a view angle of 90° are generally between 0.1 (λ ~ 600 nm-1000 nm) and 0.4 (λ~400 nm). With a measurement setup consisting of a vacuum recipient, an induction heating coil, and a thermal imaging camera, the total spectral emission coefficient of copper for λ = 0.9-1.7 μm has been determined. Further investigations will use these results for measurement of contact surface temperature in a vacuum circuit breaker test setup during switching operations.