| 摘要 |
PROBLEM TO BE SOLVED: To provide an overcurrent detecting method, which utilizes a power supply circuit and a small size current transformer for measuring a load current in a wide range, without mode switching control from an output of the current transformer. SOLUTION: In an overcurrent detecting method for detecting overcurrent of an AC circuit via a current transformer, there are provided the current transformer 2 for detecting an overcurrent, half-wave rectifying circuits D1 to D3, D4 to D6 connected in the secondary winding side of the current transformer 2 for obtaining positive and negative detection currents, detection resistance circuit (R1 to R4), connected to one set of the half-wave rectifying circuits D4 to D6 for determining the overcurrent detection range and charging circuits (D7, C1), (D8, C2) for control power supply circuit, connected to the other set of the half-wave rectifying circuits (D1 to D3. Thereby, with a primary current flowing into an AC circuit, the control power supply circuit is charged and accumulated by the other set of the half-wave rectifying circuits D1 to D3 and an overcurrent is detected by one set of the half-wave rectifying circuits D4 to D6.
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