JPS645867Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a current transformer for overcurrent relays in circuits and disconnectors, and is designed to reduce the influence of leakage magnetic flux, prevent current transformation characteristics from deteriorating, and be compact. This invention relates to current transformers for overcurrent relays.

Overcurrent trip devices that are generally installed inside circuit breakers are long-time trip devices, short-time trip devices,
They have the characteristics of instantaneous tripping, and in the event of an overload or short circuit, the opening/closing mechanism of the disconnector is tripped to open the circuit after an appropriate tripping period. A current transformer is normally used as a sensor that provides a trip signal to the overcurrent relay, but due to its application, the input-output characteristic of a current transformer maintains linearity and remains proportional up to a relatively high current range. ideal. However, current transformers for overcurrent relays installed inside circuit breakers are space-constrained and are placed close to the main current conductor of the circuit breaker. The magnetic core of the current transformer becomes saturated due to the leakage magnetic flux of It is the cause.

FIGS. 1 and 2 show a structural cross-sectional view and a rear view of an example of a three-pole circuit breaker equipped with a conventional overcurrent relay current transformer, which is the background of this invention.

In the figure, the main current path of the circuit and disconnector includes a power supply side terminal conductor 1 with a rectangular cross-sectional area, a fixed contact 2, a fixed arcing contact 3, a movable main contact 4 and a movable arcing contact 5 that are in contact with these, and one end of which is movable. A path to the load-side terminal conductor 8 is formed via a flexible lead plate 6 connected to the main contact 4 and the movable arcing contact 5, and a flexible lead plate mount 7 to which the other end of the flexible lead plate 6 is connected. has been done.

Reference numeral 9 denotes a movable contact holder, which is rotatably supported on a movable contact holder support plate 11 by a movable contact holder shaft 10, and is connected to a movable main contact 4, a movable arcing contact 5, a fixed main contact 2, and a fixed arcing contact 3 by an opening/closing mechanism 12. Circuits and disconnectors are opened and closed by moving them toward and away from each other.

An overcurrent relay current transformer 14 is installed so as to surround the load-side terminal conductor 8 of each phase that protrudes from the circuit board 13 of the circuit breaker made of an insulating material, and the current flowing in the main circuit of each phase is The secondary current converted by the winding ratio of the current transformer 14 is transferred to the static overcurrent relay 15.
When the current exceeds the set value of the static overcurrent relay 15, a magnetic flux switching magnetic trip actuator (not shown) is activated to release the release device of the opening/closing mechanism and open the circuit or disconnector. configured. The current transformer 14 for an overcurrent relay is composed of a magnetic core 17 and a secondary winding 18, which are assembled into a rectangular shape with a laminated iron plate having an opening 16 in the center through which the load-side terminal conductor 8 passes as a primary conductor. Iron core 1
Reference numeral 7 designates first magnetic core portions 17a, 17a' on which a pair of upper and lower secondary windings 18 are wound, and a second magnetic core portion 17b on which a pair of left and right secondary conductors 18 are not wound. , 17b', and the two divided secondary windings 18a and 18b are connected in series.

As shown in Figure 2, the load-side terminal conductor 8 of each phase is set as close as possible to the shortest allowable distance between the load-side terminal conductor 8 of each phase and the load-side terminal conductor of the adjacent other phase, in order to reduce the size of the circuit and disconnector. Therefore, the current transformer 14 is formed small, but the second magnetic core portion 17 of the current transformer 14
b, 17b' and the load side terminal conductor 8 passing through the opening 16
For example, at the time of a large current, leakage magnetic flux φl that partially forms a loop in the magnetic flux φ circulating through the magnetic core 17 is generated in the second magnetic core portions 17b, 17b' of the current transformer 14. As a result, the magnetic flux density increases and the second magnetic core portions 17b and 17b' rapidly saturate, so that accurate secondary output is transmitted to the overcurrent relay 15.
This will cause an error in the trip current value. In other words, the ideal characteristics of a current transformer are expressed in the current transformation characteristics of the primary current and secondary current of the current transformer shown in Figure 3 (the horizontal axis represents the primary current current and the vertical axis represents the secondary output current). Although shown by a straight line 19, the characteristics of the current transformer in the conventional device have a drawback of large errors in the high current region, as shown by a curve 20.

Therefore, the main object of this invention is to provide a current transformer for overcurrent relays for circuit breakers and circuit breakers, which has current transformation characteristics that are improved from the above-mentioned drawbacks.

In summary, this idea is based on a magnetic core body that is assembled into a rectangular shape with an opening in the center using laminated iron plates of a current transformer for overcurrent relays. By installing an auxiliary core that is laminated in the stacking direction of the magnetic core and increasing the cross-sectional area of the second magnetic core, leakage magnetic flux that does not circulate through the magnetic core body but partially forms a loop in the second magnetic core is reduced. This structure is designed to increase the saturation limit caused by the current flow and improve the current characteristics.

The above-mentioned objects and other objects and features of the present invention will become clearer from the detailed description given below with reference to the drawings.

FIG. 4 is a perspective view of the main parts of the current transformer for overcurrent relay according to the present invention, and the parts corresponding to FIGS. The laminated auxiliary core 21 is attached to the second magnetic core portions 17b, 17b' which are not wound with the secondary winding 18 adjacent to the terminal conductor of the main circuit of the other phase of the magnetic core body 17. It is installed so that it is laminated in the same direction as the laminated iron plates 17b and 17b', and this is effective for increasing the cross-sectional area of the magnetic core in a limited interphase space with other adjacent phases. .

As described above, in this case, the terminal conductors of the main circuits of each phase, which are arranged relatively close to each other in multipolar circuits and circuit breakers, are assembled into a rectangular shape with an opening 16 in the center using laminated iron plates as primary conductors. Framed magnetic core body 1
7, and the magnetic core body 17 is wound with a pair of corresponding secondary windings 18.
7a, 17a', and a second magnetic core part 17b, 17b' in which the terminal conductor of the main electric circuit of the other phase is not wound with a pair of corresponding secondary windings 18 on the adjacent side. Second magnetic core portion 1 of main body 17
Since the auxiliary core 21 is attached to 7b and 17b' so as to be laminated in the same lamination direction, the leakage magnetic flux φl that partially forms a loop is added to the magnetic flux φ circulating in the magnetic core body 17 in the conventional case. The second magnetic core portion 17 has the highest magnetic flux density.
Since the cross-sectional area at b and 17b' is increased by providing the auxiliary core 21, the saturation limit of the second magnetic core portion becomes higher, and the blockage of the magnetic flux φ circulating through the magnetic core body 17 is reduced. By increasing the cross-sectional area of the second magnetic core, which is necessary for improving the characteristics of the current transformer, without increasing the phase-to-phase dimensions of the circuit or disconnector, or reducing the width of the terminal conductor of the main circuit, A current transformation characteristic curve 22 is obtained by improving the current transformation characteristic curve 20 of the conventional device shown in FIG. 3 so that it approaches the ideal straight line 19.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a structural cross-sectional view and a rear view showing an example of a circuit or breaker equipped with a current transformer, which is a conventional device that forms the background of this invention. FIG. 3 is a current transformation characteristic diagram showing the correlation between the primary current and secondary current of the current transformer, and FIG. 4 is a perspective view showing the main parts of the device of the present invention. In the figure, 8 is a terminal conductor, 14 is a current transformer for overcurrent relay, 16 is an opening, 17 is a magnetic core body, 17
a, 17a' are the first magnetic core parts, 17b, 17
b' is a second magnetic core, 18a and 18b are secondary windings, and 21 is an auxiliary core.

Claims (1)

[Scope of utility model registration request] A magnetic core body assembled into a rectangular shape with an opening in the center using laminated iron plates with the terminal conductors of the main circuits of each phase placed relatively close to each other as primary conductors of multipolar circuits and disconnectors. a first magnetic core part on which a pair of corresponding secondary windings are wound, and an adjacent second magnetic core part on which a pair of corresponding secondary windings are not wound. A current transformer for an overcurrent relay for a circuit breaker, comprising: an auxiliary core attached to the second magnetic core portion of the magnetic core body so as to be laminated in the same lamination direction.