SU851507A1 - Current transformer - Google Patents

Description

(54) CURRENT TRANSFORMER

one

The invention relates to current transformers and can be used in instrument-making industry.

Known measuring current transformers of armor type, containing a core with two windows, multi-turn primary and secondary windings.

The disadvantage of such transformers is a relatively low coefficient of filling the window with the primary winding at high values of the primary current (tens to hundreds of amperes). .

Also known are measuring current transformers of armor type, containing a core with two windows, a multi-turn primary and secondary windings, the primary winding in turn consisting of several identical windings or coils 2.

Such transformers have a higher filling ratio of the window by the primary winding, however, an increase in the transform ratio can only be achieved by increasing the number of turns of the secondary winding, i.e. leads to an increase in the dimensions of the transformer with a constant cross section of the wire or to a decrease in the cross section of the wire, hence the magnitude of the transformable current. The closest to the offer

 is an armored type current measuring transformer, preferably small-sized, containing a core with two windows, primary in the form of a single turn and secondary winding 3.

This transformer, with specified dimensions in comparison with the known ones, has the highest transformation ratio, determined by full filling of the core windows with a wire of minimum diameter (usually about 50 µm), suitable for machine winding, however, a further increase in the transform coefficient is impossible but without increasing the size of the core, t . without increasing the size and weight of the transformer.

The purpose of the invention is to double the transformation ratio

25 without increasing the size and weight of the transformer.

This goal is achieved by the fact that in the current transformer of armor type, mainly small-sized, containing a core with two windows.

primary in the form of one coil and secondary winding, the coil of the primary winding consists of two conductors connected in parallel, the first of which passes through only one core window, and the second only through another window, the beginning of the first conductor connected to the end of the second, and vice versa.

FIG. 1 shows schematically the proposed transformer, axonometric, FIG. 2 - the same, top view; in fig. 3 shows section A-A in FIG. The measuring current transformer contains a core 1 with two windows 2 and 3, a single turn primary winding consisting of two parallel-connected conductors 4 and 5, and a multi turn turn secondary winding 6. Conductor 4 passes only through window 2, and conductor 5 and only through window 3 , the beginning 7 of conductor 4 is connected to the end 8 of conductor 5, and the beginning 9 of conductor 5 is connected to the end 10 of conductor 4 (in this case, as usual, it is assumed that the beginning of the conductor enters the core window and the end of the conductor leaves the window)

The input terminal 11 of the transformer is connected with the beginning 7 of the conductor 4 and the end 8 of the conductor 5, and the input terminal 12 with the beginning S of the conductor 4 and the end 10 of the conductor 5.

Measuring current transformer works as follows.

When the measured current is connected to the input terminals 11 and 12 of the transformer, through the conductors 4 and 5, forming a coil of the primary winding, parts of the current L respectively 3 and D flow, the ratio of which is determined by the resistance values of these conductors. The magnetic fluxes caused by these currents are summed in the core of the core 1. The summation of the fluxes takes place due to the indicated connection of the beginnings and ends of the conductor 4 and 5. The total magnetic flux in the core core interlocking with the secondary winding b causes the value of the secondary current 3ij. is determined by the sum of the currents 3, and L in conductors 4 and 5, i.e. the total value of the measured current 3.

Core flow

, FS ciD, sz; tsz,,

i

where is tC. - coefficient of proportionality between current and current Current in the secondary winding

a ° C C, 3,, where Cq - proportionality coefficient between flow and current

Transformation ratio

K 3 / Lo. 1 / Ca Ca (1)

In the well-known single-turn transformer of armor type a primary winding conductor with a full value of the measured current passes through each window of the core, and the magnetic flux in the core of the core

F; 2c, h,

The current in the secondary winding Ja C; 1Fc 2C Cg-a,

 accordingly, the transformation ratio

K 3, La O L / S, - Sa (2)

From expressions (1) and (2) it is clear

15 that the proposed transformer, other things being equal, has twice the transformation ratio.

Due to the summation of magnetic fluxes caused by the currents jj and e,

20, the difference between these currents (due, for example, to the unequal resistance of conductors 4 and 5, a change in ambient temperature, etc.) does not affect the amount of current. on precision

2J and the stability of the current transformer, and only leads to a difference in the magnetic fluxes of the right and left cores of the core F and F.

To exclude an undesirable increase in magnetic induction in the right or left rome above the usual value for current transformers in the order of 1000–2000 Hz, it is sufficient to maintain an approximate magnetic flux symmetry (with an accuracy of 20–30%)

35 for which conductors 4 and 5 are taken of approximately the same length and cross section. Then, through each of the conductors 4 and 5, passing through the window of the core, a current flows, equal to approximately 40% of the measured current D-f.

The first current transformer is designed primarily for integration into small switchboards

45 electrical measuring instruments and transducers and provides an extension of their limits of measurement (conversion) in the direction of high currents. Accordingly, the transformer itself

50 current should be small.

Claims (3)

1. Bachurin-N.I., Current Transformers. M.-L., Energie, 1964, p. 124, g38. 2. Accepted for Germany  2237054, cl. H OlF 27/28, 1977. 3. Current transformer And 1820. Technical description and instructions on operation. M., V / O Mashinopriborintorg, 1974. I. .