|
Contact protection refers to methods designed to limit the wear and degradation that occur during the normal use of contacts within an electromechanical switch, relay or contactor. ==Contact wear== Every time the contacts of an electromechanical switch, relay or contactor are opened or closed, there is a certain amount of wear. The electric arc occurs between the contact points (electrodes) both during the transition from closed to open (break) or from open to closed (make). For a very brief time, only a small section of the contact is touching (constriction), and all of the current must go through this part of the contact. The degradation caused by the high current density in the constriction during the contact make may result in a micro-weld akin to spot welding. If the current being switched is large, part of the contact is degraded or destroyed. Because there is a very small gap in the contacts for a brief time when the contacts are broken, an electric arc is also generated across the gap if the voltage is high enough. This arc caused during the contact break (break arc) is akin to arc welding, as the break arc is typically more energetic and more destructive. Contact life is terminated when the contacts stick or weld, or when excessive material is lost from one or both contacts and a good electrical make is not possible. These conditions are the result of cumulative material transfer during successive switching operations, and of material loss due to splattering. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Contact protection」の詳細全文を読む スポンサード リンク
|