SURGE PROTECT DEVICE HAVING SELECTIVE SWITCHING FUNCTION BASED SURGE SUPPRESSION DEVICE

摘要

PURPOSE: An SPD(Surge Protect Device) with a selective switching function based on a surge suppressing device is provided to stably supply power and a signal to a load by efficiently suppressing various abnormal voltages inputted to a power line and a signal line. CONSTITUTION: A voltage sensing resistor(303) is connected in parallel to an MOV(Metal Oxide Varistor) and a power source. A relay contact point and a CT(302) are serially connected to the power source and the MOV. The outputs of the voltage sensing resistor and the CT are applied to an A/D converter(304). A relay coil(305) drives the relay contact point. A microprocessor(700) controls a driving circuit(306) which supplies currents to the relay coil.