SU922668A1 - Device for measuring residual induction in current transformer core - Google Patents

Description

(54) FACILITY FOR MEASURING RESIDUAL INDUCTION IN THE CORE OF TdkA TRANSFORMER

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The invention relates to electrical engineering, in particular to electrical measuring equipment. Efficient use is assumed in the field of relay of electric power systems and electrical installations.

There are known devices for measuring the characteristics of a time-constant magnetic field, comprising a measuring coil, a mutual inductance coil, and a ballistic galvanometer P.

When measuring in the device, it is necessary to change the flow interlocking with the turns of the measuring coil. You can change the flux linkage in one of the following ways: pull the measuring katzysu out of the floor, or rotate it 180 °, rotate the measuring coil in the measured field at a constant speed, swing the measuring knob relative to its average value. neither (and so on).

However, such devices for measuring require access directly to the core and contain conflicting requirements for tightly fitting the measuring wheel to the core and a special kind of mobility.

It is also known a device for measuring magnetic parameters comprising a test and exemplary elements, a comparator unit and an indicator 2.

However, the accuracy of measurements in it is insufficient.

The purpose of the invention is to improve the accuracy of the measurement process.

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This goal is achieved by the fact that a device containing a test subject and model current transformers with serially connected primary windings and resistors connected to their secondary windings,

Claims (2)

15 and an electrical metering device, an integrator, two adders, a nonlinear functional converter, a comparison unit and three massaging blocks, the inputs of two of which and the integrator input are connected to the resistor of the tested transformer, the input of the third scaling unit to the resistor of the sample transformer, its output are entered and the output of the second scaling unit through 3 the first adder and the nonlinear functional converter are connected to the first input of the comparison unit, the output of the integrator and the first scaling unit h Res second adder - a second input of the comparator associated with the recording device. The drawing shows a block diagram of the device. Test current transformer 1 is loaded by a resistor 2, which converts the secondary current into a proportional voltage. The exemplary current transformer 3 is designed to accurately measure the primary current of transformer 1. Transformer 3 is also loaded with a resistor 4, the voltage on which is proportional to the primary current of transformer 1, because transformer 3 must work with almost no noticeable error, which ensures its proper performance and proper secondary load ; The device also contains an integrating unit 5; scaling blocks 6, 7 and 8 serve to scale, i.e., to increase or decrease in the required size the magnitude of the voltages applied to the input, thereby introducing the necessary constant coefficients. Adders 9 and 10 sum the voltages applied to their inputs. The H-linear functional converter 11 is designed to ensure that the output voltage is dependent on the input voltage of the same kind as the H (H) relationship in the core of the transformer under test 1. The comparison unit on the resistors 12 and 13 performs the subtraction, which results in a constant voltage representing the residual induction of Br as it was before the measurement started in the core of the transformer 1. This constant value is measured with the indicating device 14. The device operates as follows. The primary and secondary currents of the transformer 1 under test are transformed with resistors 2 and 4 connected to the secondary windings of the TR-nsformators 1 and 3 into measurable proportional lines, which are then transformed by integrating, scaling, summing, and nonlinear blocks and subtract from each other and the result of the subtraction is measured by the indicating device. In the device, an exemplary pre-demagnetized transformer 3 is used to accurately measure the primary current flowing in the primary winding of the transformer 1. For example voltage proportional to the primary current and the secondary of the transformer under test 1, are removed with the resistors 2 and 4, respectively. The voltage across resistor 2 is proportional to the secondary current with a coefficient k, which depends on the resistance of resistor 2. The voltage on resistor 4 is proportional to the secondary current of transformer 3, and since it is exemplary, it is proportional to the primary current flowing in the primary windings of transformers 1 and 3, connected in series with the coefficient n, which depends on the transformation ratio of the transformer 3 and the resistance value of the resistor 4. - The voltage from the resistor 2 is fed to the input of the integrating unit 5 with the R / kWjS and the inputs to the two scaling units: 6 with the coefficient L / kW2S and 7 with the coefficient Wj / kl. The output voltage of the integrating unit 5 and the scaling unit 6 is supplied to the adder 9, the voltage at the output of which represents induction in the core of the transformer 1, taking into account the residual inductance Br. The voltage from the resistor 4 is applied to the scaling unit 8 with the coefficient Wj / ri, from which the output voltage of the scaling unit 7 is subtracted, so that the output of the adder 10 produces a voltage that represents the voltage H in the core of the transformer 1. This last goes to the input of a non-linear functional converter 11, which effects the output-output B (H) characteristic of the core of transformer 1, and the output of the converter 11 yields a voltage representing induction B in the transformer core pa 1 due to current ij. Resistors 12 and 13 subtract B-B, i.e., subtract the corresponding voltages, resulting in a voltage that represents the residual induction of W in the core of the tested transformer 1, which it was before the measurements began. This voltage is measured by the indicating device 11 with the appropriate graduation. Thus, by achieving the objective of the invention, the process of measuring residual induction in transformer cores is greatly simplified. In the technical aspect, this will allow more accurate reading of the actual characteristics of the transformers used and their parameters, which should improve the measurement accuracy. The economic effect will be in reducing the cost of measurement, due to their acceleration. Apparatus of the Invention A device for measuring the residual inductance in the core of a current transformer, containing a test and exemplary current transformers with series-connected primary windings and resistors connected to their secondary windings, and an electrical measuring device, characterized in that, in order to improve measurement accuracy, In addition, an integrator, two adders, a non-linear functional converter, a comparison unit and three scaling units, two of which and an input are introduced The ora are connected to the resistor of the transformer under test, the input of the third scaling unit to the chopper of the sample transformer, its output and the output of the second scaling unit through the first adder and the non-linear functional converter are connected to the first input of the comparator unit, the output of the integrator and the first scaling unit through the second adder - to the second input of the comparator unit associated with the recording instrument. Sources of information taken into account in the examination 1. Electric measurements. Under. ed. A.V. Fremke. L., Energie, 1973, p. 263,265. 2. USSR author's certificate number 664133, cl. G 01 R 33/12, 1975. ABOUT g about but