SU771738A1 - Current transformer - Google Patents

Description

one

The invention relates to instrument transformers, in particular, current transformers for measuring alternating current, and can be used in various automation devices, for example, as current sensors for non-contact protection devices embedded in low-voltage electrical apparatus .10

Current transformers with an oval core are known, in which the secondary winding is evenly distributed around the perimeter of the core, the primary winding is made in the form of a rod 5 (bus) passing through the center of the core window C.

The bus transformer has low manufacturability and increased dimensions.

The closest to the technical aspect of the present invention is a current transformer consisting of a closed magnetically forgive rod, an electrode made of a ferromagnetic material, a secondary winding, 25 consisting of two sections connected in series and located on the cores of the magnetic core and primary winding , made in the form of current-carrying bus of rectangular cross-section, ZO

in which one pair of faces is adjacent to the secondary winding, and another pair of faces to the magnetic core 2.

In order to reduce overall dimensions, the gap between the cores of the core and the side faces of the current-carrying bus is minimal and is determined by the required insulation strength between the primary and secondary windings. The disadvantage of these transformers is a significant current error in the operating current range, associated with the presence of scattering flows of the primary winding, which are closed along the air gap between the bus and the core and the throttle.

The flows of the scattering of the primary winding are summed in the core with the working flow, which causes saturation of the section of the core and, consequently, an increase in the current error of the sensor in the operating range of the currents.

The aim of the invention is to reduce the current error of the current sensor without increasing its size and while maintaining the desired thermal conditions of the apparatus.

Claims (2)

The goal is achieved by the fact that in the body of the conductive bus of the primary winding, open grooves are made on the side of the magnetic conductor; In other words, the grooves are arranged in pairs in planes parallel to the plane of the magnetic circuit, with a pitch in the range of 0.10-0.15 width of the tire. The design of the proposed current transformer is shown in the drawing. The current transformer consists of a closed core magnetic conductor 1 made of laminated ferromagnetic material, a secondary winding consisting of two sections 2 and 3 connected in series and located on the rods of the magnetic pro- tect 1, and the primary winding made in a current-carrying bus 4 rectangular cross section, in which one on a pair of faces adjoins the secondary winding, and another pair of faces adjoins the magnetic conductor. In the body of the conductive bus 4 of the primary winding on the side of the magnetic core 1 there are open grooves 5 extending to the outer surface of the faces C, size H (height), the depth of the grooves is within 0.10-0.15 Width B, and the same number of grooves goes to each of the faces with the size H, and the grooves are arranged in pairs in planes parallel to the plane of the magnetic circuit 1 with a pitch of 0.10-0.15 width of the tire. A rough picture of the current distribution in the busbar bus is shown in the drawing. In this case, the working flow FR is closed through the magnetic conductor. The flow of the primary winding closes through the air, does not penetrate into the magnetic core due to the increase in the non-magnetic gap, due to the presence of grooves that reduce the cross section of the conductor, at their location with the necessary step more than 0.15 c). When a current flows through a bus, which has grooves of the required depth (not more than 0.15 V) and a sufficiently small width, its teddle mode practically does not change due to the fact that the material (copper, aluminum) of the bus duct has a high thermal conductivity. , and its heat transfer remains almost unchanged when current flows for a time determined from the time-current characteristics of the protection device. Thus, the invention provides a significant reduction in the current error of the transformer due to the lack of saturated sections of the magnetic circuit and the invariance of the thermal regime of the device. The proposed current transformer can be used in current sensors. In this case, the sensor has a linear input-output characteristic in the range of operating currents (up to 10 times the nominal value) power sufficient to power the non-contact functional units of the protection device, minimum dimensions when satisfying the manufacturability requirement. The linearity of the sensor characteristics in the range of operating currents makes it possible to significantly reduce the complexity and power consumption when calibrating contactless protection devices with the proposed sensor, since calibration can be performed not on power equipment and the flow of real overload and short circuit currents, but using a low-power voltage source simulating linear current sensor output. Claims of the Invention A current transformer consisting of a rod magnetic circuit, a secondary winding made of two. The sections connected in series and located on the cores of the magnetic conductor, and the primary winding, made in the form of a conductive bus of a rectangular cross section, y. one pair of faces adjoins the secondary winding, and the other pair of faces adjoins the magnetic core, which is characterized by the fact that, in order to reduce the current error, in the current-carrying bus of the primary winding there are open grooves extending to the outer surface of the faces on each of the faces the same number comes out, the grooves are arranged in pairs in planes, the first one is the plane of the magnetic circuit, with a pitch of 0.10-0.15 width of the tire, the depth of the grooves is within 0.10-0.15 of the width of the tire. Sources of information taken into account in the examination 1. Kazansky V. Ye. Current transformers in relay protection circuits. M., Energie, 1969, p. nineteen. 2. Mogilevsky 1. V., Rainin V. Ye., Soskov A. G., Ustimenko B. Yu. Non-contact protection devices for low-voltage electrical apparatus. M., Energie, 1971, p. eleven. H -Fr