| 摘要 |
PURPOSE:To improve detection accuracy of fault current level, by converting current flowing through an AC path into unilateral current through a rectifying circuit and feeding the converted current entirely through a detection resistor. CONSTITUTION:Output from a current transformer 21 for detecting the current flowing through an AC path 1 is converted through a rectifying circuit 30 into unilateral current, which is then fed entirely to a power source circuit 500 and current detection resistors 40, 41. Potentials across the current detection resistors 40, 41 are amplified by differential amplifiers 60, 61, outputs from which are fed to a time limit circuit 70 in order to control a switch circuit 120 and to control a load switch contact 201 through an electromagnetic trip device 80 and an interrupting mechanism 100. Test signal generating circuits 13, 14 switch the simulated input voltages fed from DC power sources 19, 20 to the differential amplifiers 60, 61 and enables field check of the trip characteristics. |
