Residual current circuit breaker

Abstract

An electric leakage circuit breaker includes: a zero phase current mutual-inductor (3) detecting an electric leakage current of a multi-phase alternating circuit (1); an electric leakage detection circuit (4); a tripping apparatus (5) which turns off a contact of the alternating circuit (1) based on an output signal of the electric leakage detection circuit (4); a testing circuit feeding a testing current (It) for simulating electric leakage by turning on a testing switch (6a); a filtering and amplifying unit (10) provided between the zero phase current mutual-inductor (3) and the electric leakage detection circuit (4), and including an operation amplifier (10a) used as an amplifying member so as to amplify a secondary side output current (Is) of the zero phase current mutual-inductor (3) according to an amplifying level of a set value of a sensibility setting unit (11). In the electric leakage circuit breaker, an active filter circuit comprising the operation amplifier (10a) is contained in the filtering and amplifying unit (10). The active filter circuit is switched from a low-pass filter circuit to a band-pass circuit during testing so as to remove noise and offset components which result testing faults.

Description

technical field [0001] The present invention relates to a leakage circuit breaker used to detect leakage in a power distribution system, so as to prevent leakage accidents before they occur, in particular to a leakage circuit breaker provided with a test circuit for determining the function of leakage tripping. Background technique [0002] It is well known that an earth leakage circuit breaker is provided with a test circuit for confirming the operation of the earth leakage tripping function (see Patent Document 1, for example). FIG. 4 is a block diagram of the circuit disclosed in Patent Document 1, which shows an example circuit of the relevant earth leakage circuit breaker provided with the test circuit. [0003] In FIG. 4, reference numerals 1, 2, and 3 respectively denote a three-phase alternating current (AC) circuit, a main circuit switch contact device for switching the AC circuit 1, and detecting the current in the AC circuit 1 by using the AC circuit 1 as a main w...

AI Technical Summary

Problems solved by technology

This problem is that the magnitude of the output circuit Is fed from the secondary side of the zero-phase current transformer 3 to the leakage detection circuit 4 is insufficient (too small) to be smaller than the threshold value set by the leakage detection circuit 4, which hinders the normal function of the leakage test operate

Images