A test method for 50 Hz capability of vacuum interrupter materials

This investigation method allows an excellent comparison of the interruption behavior of contact materials in real vacuum tubes by using small cylindrical contact samples (12 mm diameter) in a special experimental setup. The described investigations were carried out with different CuCr materials in an ultrahigh 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 (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 re-ignition 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 for different contact materials.