| 摘要 |
PURPOSE:To reduce a surge voltage taking place in a switching process so as to increase capacity when a breaker is formed with a pair of fixed contact and movable contact arranged inside a vacuum valve by selecting a material having a low surge properly and a material having high breaking performance as contact materials and using the low surface material on the negative electrode side at the time of load current breaking. CONSTITUTION:Three vacuum valves 21A, 21B, 21C are housed in a vacuum breaker 20. Because all of them have the same structure, the valve 21A is selected as a typical one to show its structure consisting of a fixed electrode and a movable electrode installed facing each other. Namely, a contact 23A is provided on a surface facing to a fixed electrode 22A and a contact 23B is also provided on a movable electrode 22B. In this construction, Ag-WC or a material having a low surge property containing a large quantity of a high vapor pressure material is used for the contact 23A and a material with high breaking property such as Cu-Cr containing 90% or more copper, for instance, is used for the contact 23B. Further, materials having low surge properties are used for the contact 25A and contact 25B with high breaking performance and the same materials as those of contacts 25A and 25B are used for contacts 27A and 27B respectively. Also, the electrode opening phase is specified by detecting the phase of current. |
