SU624173A1 - Arrangement for measuring instantaneous current value - Google Patents

Description

I

The invention relates to the field of electrical current measuring devices.

A device for measuring the instantaneous current value is known, comprising a filter, a coarse current sensor with inputs for the measured current and control, a coarse current sensor output connected to the filter input, a power source.

However, in a power circuit, it is necessary to install a choke, which has an effect on the circuit to measure its current, which is not always acceptable and; reduces the accuracy of the device.

To improve the measurement accuracy, a second coarse current sensor and two threshold elements, each of which inputs are connected to the coarse current sensor outputs, are introduced into the instantaneous current measurement device, and the output of the first threshold element is connected to the control input of the first coarse current sensor, and the output of the second threshold element is connected to the control input of the second coarse current sensor, the output of the first threshold element and to the positive star of the power source, the negative terminal of which is connected with corresponding k.pe Mami both threshold elements, both coarse current sensor and a filter.

The drawing shows the scheme of the proposed device for measuring the instantaneous current value.

The device contains two threshold elements 1 and 2 with input terminals 3, 4 and 5, b and output terminals 7 and 8, a coarse current sensor 9 consisting of keys 10 and I (for example,: trans | Cis 6-diode), the resistor 12, the measuring transformer 13 on the core with a rectangular fly

hysteresis with two coils 14 and 15, while terminal 16 is the output of sensor 9. The device also contains a second sensor 17, consisting of two to 18 and 19, peSTficTopa

Claims (2)

20, a measuring transformer 21 on a core with a rectangular hysteresis loop with two windings 22 and 23, with terminal 24 being the output of sensor 17. In addition, a high-pass filter 25 and a constant-voltage source 26 are included in the device by bus. The device is connected to the measured current circuit through terminals 27 and 28. The output of the device is terminal: 29. The sensors 9 and 17 work based on the principle of transforming the measured current with the power of transformers 13 and 21. Direct current transformation of any sign and alternating current any phase from the primary windings 14 and 22 (measuring bus) to the secondary 15 n 23 occurs because the transformer cores 13 and 21 continually re-magnetize the core. Continuous magnetization reversal of the transformers 13 and 21 is due to the fact that sensor 9 through lement 1 and the sensor 17 through the rigid element 2 covered nonlinear positive feedback. Therefore, at the moment when the transformer core enters the saturation region, the output of the corresponding sensor generates a switching signal, which switches the threshold element in the feedback circuit, which leads to a change in polarity of the remagnetizing voltage of this transformer, i.e. . Sensor 9 with threshold element i and sensor 17 with threshold element 2 form two rectangular-shaped relaxation oscillators, KOTOpwe in an independent mode of operation would have a generation frequency determined by the time of complete magnetization of the core of its own transformer. In the device, the cross section of the transformer core 13 is chosen larger than the cross section of the transformer core 21, the threshold threshold threshold is less than the threshold threshold of element 2, the number of turns of the windings 15 and 23, and the resistances of the resistors 12 and 20 are equal to saturating the core of the transformer 21 at the output of the sensor 17, a switching signal arises, which is fed to the 9THOTES of elements 1 and 2. Initially Uf (reaches the threshold of element 1 and switches on this element, which leads to a change in the polarity of the remagnetizing voltage on the winding 15 of transformer 13). After a certain period of time, the switching signal reaches the threshold of element 2, which leads to a change in polarity of the switch magnetizing voltage on the winding 43 of the transformer 21. From here, it can be seen that the oscillation frequency of the left oscillator will be equal to the oscillation frequency of the right oscillator. Thus, the transformer core 21 will be remagnetization but a FULL hysteresis loop with a small approach to the saturation region, which is necessary to obtain a switching signal, and the transformer core 13 will be re-magnetized through an acoustic hysteresis loop without a saturation region. time is observed equal to the ampere-turns, t, e, equal currents will flow through the secondary windings 15 and 23, and equal to each other and opposite in sign voltage will appear on the resistors 12 and 20 mo proortsionalny emomu measured current and the output signals are SDT. The output signal of the device uses the signal from the output of sensor 9, since it has a significantly lower ripple level than the signal from the output of sensor 17. The output signal of sensor 9 is fed to a high-pass filter 25, which smoothes small spikes and gaps of less than a microsecond duration due to switching processes in the current sensor. It can be considered that the filter 25 does not contribute to the lag at the operating frequencies of the measured current, since it has a small time constant. The combined operation of two sensors makes it possible to reduce low-frequency emissions and dips resulting from the entry of transformer cores into the usn region, separately taken sensor to a level of no more than + 1%. from the maximum output signal. The level of these pulsations is determined by the values of the thresholds of elements 1 and 2, which, in turn, are chosen taking into account the magnetizing currents of the transformers. Consequently, it is necessary to choose paraglutra of transformers 13 and 21 so that the magnetizing current is many times less than that brought to the secondary windings of the Measured current. An invention for measuring an instantaneous current value comprising a filter, a coarse current sensor with measured current inputs and control, a coarse current sensor output connected to a filter input, a power supply source, characterized in that, in order to improve the measurement accuracy, A second coarse current sensor and two threshold elements are entered into it, the inputs of each of which are connected to the outputs of coarse current sensors, while the output of the first threshold element is connected to the control input of the coarse sensor, current, and the output of the second thresholds the first element is connected to the control input of the second coarse ika current date, output of the first threshold element and a plus terminal of the power source, the negative terminal of which is coupled with the appropriate. terminals of both threshold elements, .Obio rough current sensors and filter. Sources of information taken into account in the examination: 1. USSR author's certificate g 194162, cl. Q 01 K 19/04 1965