JPH0246022Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a magnetic shielding structure for a zero-phase current transformer used in an earth leakage breaker.

Conventionally, zero-phase current transformers used in earth leakage circuit breakers have residual current characteristics, and if this characteristic is poor and the starting current of the device flows, such as when starting a motor, an output will be generated in the secondary winding and the earth leakage will be interrupted. A magnetic shield is provided to prevent the device from malfunctioning. The arrangement of the primary conductors near the through-hole entrance and exit of the zero-phase current transformer is symmetrical and the longer the straight section is, the better the balance characteristics will be. There is. For large rated currents, a single or stacked layer of several sheets is used to prevent the local magnetic field generated by this bent primary conductor from producing an output in the secondary winding of the zero-phase current transformer. A magnetic shielding plate is provided. When stacking magnetic shielding plates, it becomes expensive because it is necessary to insulate the layers to prevent heat generation due to eddy currents.

In view of the above, the present invention provides an inexpensive magnetic shielding structure for a zero-phase current transformer.As explained below with reference to the drawings, 1 is a zero-phase current transformer, and its through hole 2 has 3
The phase primary conductors 4, 5, and 6 are inserted through the S phase conductor 5.
are formed in a straight line, and the R and T phase conductors 4 and 6 are bent near the through hole 2 on both sides, and the bent portions 9, 9',
10, 10'. Numeral 7 is a magnetic shielding plate that sandwiches the zero-phase current transformer 1 and is provided with a plurality of magnetic shielding plates on both sides.
The primary conductors 4, 5, 6 pass through the bent portions 9,
9'10, 10' and the zero-phase current transformer 1.

The magnetic shielding plate 7 is fitted into a groove 12 provided on the inner surface of the side walls 11, 11 of the case 14, and a gap 13 is formed to provide insulation. After the magnetic shielding plate 7 is fitted into the groove 12 of the case 14, the upper end is pressed by the cover 15 and fixed.

The magnetic shielding plate 7 is divided into two parts, an upper part 16 and a lower part 17, as shown in FIG.
The assembly work efficiency can be improved simply by placing the primary conductors 4, 5, and 6 into the grooves 2 and then fitting the upper part 17 into the groove 12.

As described above, in this invention, a magnetic shielding structure with air gaps is constructed by fitting a plurality of magnetic shielding plates into the grooves in the side wall of the case, and the balance characteristics of a zero-phase current transformer can be improved. It has practical effects.
(1) A gap is formed simply by fitting the magnetic shielding plates into the grooves, and the insulating material between the magnetic shielding plates can be omitted, simplifying assembly, resulting in an inexpensive zero-phase current transformer shielding structure. (2) The number, mounting position, and material of magnetic shielding plates can be freely selected according to the rated current and rated sensitivity current.

[Brief explanation of drawings]

The figures show one embodiment of the shielding structure of the zero-phase current transformer according to the present invention. Figure 1 is a front view of the main parts of the earth leakage breaker with the lid removed, and Figure 2 is the main parts of the earth leakage breaker. 3 is an exploded perspective view of the main part, and FIG. 4 is a diagram showing another embodiment of the magnetic shielding plate. 1 is a zero-phase current transformer, 4, 5, 6 are primary conductors, 7 is a magnetic shielding plate, 9, 9', 10, 10' are bent parts, 1
2 is a groove.

Claims (1)

[Claims for Utility Model Registration] 1. A zero-phase current transformer 1 through which three-phase primary conductors 4, 5, and 6 pass, and bent portions 9 of both sides of the zero-phase current transformer 1 and the primary conductors 4, 6. . Groove 1 formed
2, a magnetic shielding structure for a zero-phase current transformer in which a gap 13 is formed between a plurality of magnetic shielding plates 7 and the upper end of the magnetic shielding plate 7 is locked to a cover 15. 2. The magnetic shielding structure for a zero-phase current transformer according to claim 1, which is a registered utility model, in which the magnetic shielding plate 7 is divided into two parts, and both ends of the upper part 16 and the lower part 17 are fitted into the grooves 12.