| 摘要 |
<p>A two-pole contactor includes a contact assembly (24) for making and breaking contact between a pair of fixed contacts (8, 10) at each pole. The contact assembly is a plastics moulding carrying a resiliently supported shorting bar and is coupled to a plunger of a solenoid. In order to make a contact, the plunger accelerates the contact assembly towards the fixed contacts, until the contact bar touches the fixed contacts. The plunger and the remainder of the contact assembly then continues to move through a predetermined distance, loading the resiliently supported shorting bar against the fixed contacts. To break contact, the procedure is reversed. The solenoid has two plungers slidable within a common bore and separated by a compression spring. Permanent magnets situated at each end of the solenoid core induce an attractive force between the plungers. When the separation between the plungers is smaller than a threshold separation, the magnetic attraction overcomes the spring force and the plungers latch together. When the separation between the plungers is greater than the threshold separation, the force exerted by the spring is greater than the magnetic attraction and so the plungers de-latch in a separated position, in which the contacts at both poles of the contactor are open.</p> |
