| 摘要 |
A reduced arcing contact switching circuit. It is desirable to control the switching of electrical contacts so that opening and closing occur at the time when zero power is being transferred to the load so as to substantially reduce arcing at the contacts and thus extend contact life. In a purely resistive circuit, for example, the supply voltage and current will be in-phase and contact switching should occur when the current and voltage signals pass through zero degree phase angle. Control of contact switching is accomplished with this invention by producing a count value that represents the phase angle at which contact movement should be initiated, so that the actual closing or opening will occur at the desired phase angle. When the count value and a preselected count are approximately equal, a flip-flop is enabled to pass the control information (open or close contacts) to a relay driver. The relay driver energizes or deenergizes (as the case may be) the relay to open or close the contacts.
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