DIRECT GROUND TYPE CONSTANT-CURRENT CIRCUIT

摘要

PURPOSE:To prevent an output current from exceeding at ground-fault time by inputting a voltage of the tertiary winding generated on the basis of the unbalance of the first and second windings of a current transformer to an overvoltage protecting circuit when an output terminal is arced. CONSTITUTION:The first and second windings I, II of a current transformer 20 are connected in series with the secondary side output circuit of a main transformer 3. The unbalance voltage generated in the tertiary winding III of the transformer 20 is detected by a rectifying and smoothing circuit 30. This unbalanced voltage is applied through a diode 21 to an overvoltage detector 14 to control a controller 13.