A test method for 50 Hz interruption capability of contact materials for vacuum interrupters

This investigation method allows an excellent comparison of the interruption behavior of contact materials in real vacuum tubes by using small cylindric contact samples (12 mm diameter) in a special experimental setup. The described investigations were carried out with different CuCr materials in an ultra high vacuum test vessel. For the test an apparent current density similar to the stress in real switches is applied to the contact materials of reduced size. A high current circuit with a current of 10.7 kA peak is used for the interruption check. After current zero a Weil-Dobke voltage superposition circuit applies a transient recovery voltage (up to 36 kV, 41 KHz) to the open gap to test the restrike behavior. From the measured data the percentage of successful interruptions of the total number of tests and the reignition times were taken as quality criteria. Compared to interruption capacity measurements with real breakers the results of the developed test method show very similar rankings of different variants of contact materials