An Interrupting Capacity Model of Axial Magnetic Field Vacuum Interrupters with Slot Type Contacts

This paper introduces a new interrupting capacity model for slot type axial magnetic field (AMF) vacuum interrupters (VIs), which is as I=k times D² times B_z ^alpha. It means that interrupting capacity of a slot type AMF VI is proportional to contact area times alpha^th power of AMF. When contact gap increase, AMF weakens. Thus interrupting capacity decreases with increase of contact gap according to the model. The model is validated by short circuit current interruption tests with contact diameters of 48mm, 58mm and 66mm and contact gaps of 8mm, 11mm and 14mm. Even though there is some difference between the model predictions and experimental results, the model predictions are close to rated short circuit interrupting capacity of tested vacuum interrupters at contact gap of 8mm. More test results are needed to support the new model and AMF distribution should be considered to improve the model. After that, the new model is expected to be used until high voltage VIs that has long contact gaps