RU2300774C1 - Measuring converter - Google Patents

Abstract

FIELD: the proposed invention refers to electro-measuring technique and may be used for precision measurements of the amplitude of constant and alternate currents and voltages including unsinusoidal form.

SUBSTANCE: the technical result from realization of the given invention is in increasing accuracy and speed of measuring of currents and voltages and rigid synchronization of the modes of the work of the principal elements of the measuring converter and of the forming by it of the latitudinally-impulse modulated voltage. The proposed measuring converter has a sensor-converter of the amplitude of measured current into impulse voltage fulfilled on a ferromagnetic transformer in which the primary winding is connected in parallel with section of the circuit of measured current, the winding of magnetic biasing is connected with the source of current magnetizing, the field coil is connected with the timing inputs of the impulse generator and a compensation winding is connected with the output of current amplifier of degenerative feedback whose input is connected with the current output of the demodulator, whose paraphase outputs are the outputs of the measuring converter. At that the output of the generator is connected with the input of the synchronizer and through the first and the second biased multi-vibrators is connected with corresponding inputs of the phase detector whose output is connected with the input of the demodulator and the outputs of the synchronizer are connected correspondingly with the inputs of starting input and of prohibition of the generator's work.

EFFECT: increases accuracy and speed of measuring currents and voltages.

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Description

The invention relates to electrical engineering and can be used for precision measurements of the amplitude of direct and alternating currents and voltages, including non-sinusoidal forms, as well as in all types of electricity meters and information-measuring systems of the electric power industry.

Increasing the accuracy and speed of precision measurements of constant and alternating currents and voltages, especially non-sinusoidal form, is one of the urgent tasks of modern metrology.

For this purpose, current sensors based on magnetic modulators, which are a ferromagnetic transformer, are used in which the reference voltage of the high-frequency excitation is applied to one of the secondary windings and the value of the measured current flowing through the primary winding is judged by the change in its parameters in the measuring winding .

The disadvantage of such sensors is the presence of spurious modulation in duration if the input action is converted to a pulse-frequency modulated (PFM) voltage, or in frequency if the input action is converted to a pulse-width modulated (PWM) voltage, which leads to measurement errors, which prevents widespread adoption of such devices.

More complex converters use multiple conversion in the following order: the amplitude modulation (AM) of the input signal is converted to PFM, the PFM is converted to PWM, and the PWM is converted to AM voltage again or used to machine the measurement results.

Closest to the proposed measuring transducer is a measuring transducer of current and voltage to frequency-modulated voltage pulses [1], containing a ferromagnetic transformer in which the primary winding is connected to a current-limiting resistor, the compensation winding is connected to the output of the feedback voltage amplifier, the magnetization winding is connected with a bias current source, the field winding is connected to the timing inputs of the generator, the output of which is the output of the current-voltage and voltage transducer, as well as a pulse-width converter, which includes a counter-divider by "n", the counting input of which is connected to the output of the mentioned generator, and the input of the resolution of the count is connected to the inverse output of the asynchronous trigger, the zeroing input and the setting the inputs of which are connected respectively to the output of the counter-divider by "n" and to the output of a voltage-controlled generator, the control input of which is connected to the output of the sample-memory device, the signal input of which is connected is connected to the output of the demodulator, the differential inputs of which are connected to the paraphase outputs of the asynchronous trigger, the outputs of which and the output of the demodulator are the outputs of the measuring transducer, while the output of the demodulator is connected to the signal input of an adjustable amplifier, the control input of which is connected to the analog output of the calibrator, the pulse output of which is connected with the control input of the device “sampling-storing”, in addition, the calibrator has an input for switching an external source of commands and whether synchronization.

A significant drawback of such a measuring transducer is the multiple conversion of input signals and the absence of tight synchronization of the operation of its elements, which leads to a complication of its circuit and a decrease in the accuracy and speed of measurements.

These shortcomings can be eliminated by eliminating the intermediate PFM conversion and introducing tight synchronization of the operating modes of the main elements of the measuring transducer.

The technical result of the proposed solution is to increase the accuracy and speed of measuring currents and voltages and tightly synchronize the operating modes of the main elements of the measuring transducer and the PWM voltage generated by it.

This result is achieved by the fact that in a measuring transducer containing a sensor-converter of the amplitude of the measured current to the pulse voltage, made on a ferromagnetic transformer, in which the primary winding is connected in parallel with a section of the measured current circuit, the magnetization winding is connected to the magnetization current source, the excitation winding is connected to timing inputs of the pulse generator, and the compensation winding is connected to the output of the negative feedback current amplifier, input which is connected to the current output of the demodulator, the paraphase outputs of which are the outputs of the measuring transducer, a synchronizer, a first and second standby multivibrators and a phase detector are additionally introduced, while the generator output is connected to the synchronizer input and connected to the corresponding inputs of the phase detector through the first and second standby multivibrators, the output of which is connected to the input of the demodulator, and the outputs of the synchronizer are connected respectively to the inputs of the start and prohibition of the generator.

The essence of the proposed technical solution is that to improve metrological characteristics, such as increasing the accuracy and speed of measurements and ensuring tight synchronization of the generated pulses, the known measuring transducer is supplemented with a synchronizer, two waiting multivibrators and a phase detector, and the intermediate function of the PFM conversion is excluded in it, which made it possible to expand the dynamic range and improve the accuracy of measuring constant and alternating currents and voltages, in particular and non-sinusoidal.

Comparison of the proposed solution with the known shows that it has a new set of essential features, which, complementing the known features, allow to successfully achieve the goal.

Figure 1 shows the structural diagram of the measuring transducer, and figure 2 - plot voltage U _A , U _B , U _B , U _G , U _D and U _E at its main points A, B, C, D, D and E .

The measuring transducer contains input terminals 1 and 2, a ferromagnetic core 3, a primary winding 4, a magnetizing winding 5, a compensation winding 6, an excitation winding 7, a generator 8, a synchronizer 9, two waiting multivibrators 10 and 11, a phase detector 12, a demodulator 13, an amplifier negative feedback current 14, bias current source 15 and output terminals 16 and 17.

The proposed measuring transducer (IP) works as follows:

the input current I _in , created in the primary winding 4 by the measured current source through terminals 1 and 2, creates in the ferromagnetic core 3 a magnetic field corresponding to its size and sign, which changes the magnetic permeability of the ferromagnetic core 4 in proportion to its degree of magnetization.

A change in the magnetic permeability leads to a change in the inductance of the field winding 7, which is the timing circuit of the generator 8, which, in the absence of a synchronizer 9, would form a voltage normalized by the PFM amplitude. But the joint work of the generator 8 and the synchronizer 9 in the indicated inclusion avoids the intermediate PFM conversion and immediately obtain the voltage normalized by the PWM amplitude at the output of the generator 8, and this is done as follows.

The synchronizer 9 continuously generates short, following with a constant period T, voltage pulses U _A (Fig.2, a) start and synchronization of the generator 8.

The first after starting the output voltage pulse U _B (Fig.2, b) of the generator 8 with its slice (trailing edge) starts the synchronizer 9, which generates a voltage pulse U _B (Fig.2, c) of the prohibition of the operation of the generator 8, which exists until a new pulse appears start generator 8, after which the process is periodically repeated.

Therefore, the generator 8 during the period T generates only one voltage-normalized voltage amplitude U _B , the duration τ of which depends on the amplitude and sign of the measured current and can vary in the range from 0 to T.

For the convenience of working with alternating signals in the absence of a measured signal, the value of τ is chosen equal to the half-period, that is, τ = T / 2. With a positive value of the signal, the value of τ changes in the interval 0≤τ≤T / 2, and with a negative value of the signal, the value of τ changes in the interval T / 2≤τ≤T.

Thus, at the output of the generator 8, we received a single-cycle synchronous PWM with modulation by a slice of the generated voltage pulses U _B with a repetition period T.

To increase the sensitivity and expand the dynamic range of the measured currents and voltages, the first standby multivibrator (HMV) 10 is started by the voltage front U _B , and the second HMV 11 is started by cutting the voltage pulses U _B.

Both LMWs, 10 and 11, form voltage amplitude pulses U _G (figure 2, d) and U _D (figure 2, d), normalized by amplitude, whose duration is constant and equal to T / 2 in value.

The only difference between the voltages U _G and U _D is the shift in time (phase) by an amount equal to the time of existence of the voltage pulses U _B.

By the coincidence of the phases of the voltage U _G and U _D (an equal coincidence of low and high potentials), the phase detector 12 generates voltage pulses U _E (Fig.2, e) containing doubled information about the modulation coefficient of voltage pulses U _B.

The low-frequency component isolated by the demodulator 13 from the output voltage U _{E of the} phase detector 12 is supplied to the paraphase terminals 16 and 17, which are the output of the transmitter, and from the current output to the input of the negative feedback current amplifier (OOS) 14, the output current of which acts on the compensation winding 6, forming in the ferromagnetic core 3 the magnetic field necessary to compensate for the losses in the core 3, to increase the linearity of the conversion of the measured current into PWM voltage, as well as to weaken the effect of SP on destabilizing factors.

To work with alternating input signals and determine their sign, the magnetization of the ferromagnetic core 3 from the bias current source 15, the output current of which affects the magnetization winding 5, is carried out.

The current amplifier 14 OOS and compensating winding 5 turn the PM into an effective automatic control system (CAP), closed through the resulting magnetic field created by the currents of the windings 4, 5, 6 and 7 in the ferromagnetic transformer 3.

The impact of such a CAP with a deep OOS in the magnetic field has a stabilizing effect on the operating mode of the IP and provides a precision conversion of the input analog signals to high-frequency PWM voltages U _B and U _G (Fig.2, b and d), which are convenient to use for machine processing contained in information, precision decoding of the voltage U _G and the formation on terminals 16 and 17 of low-frequency paraphase voltages, the amplitude of which is strictly proportional to the level of the measured current or voltage.

The high sensitivity and high (hundreds of kilohertz) conversion frequency make it possible to minimize the size and weight of the ferromagnetic transformer 3 and the transformer in general, make it possible to connect the transformer to the current conductor in parallel, without breaking the circuit of the measured current.

The technical result of the application of the invention, in addition to increasing the accuracy and speed of measurements, expanding the dynamic range of the measured currents and voltages, as well as tight synchronization of operating modes and generated voltage pulse IPs, is to improve technical characteristics, such as:

- stabilization of the parameters included in the composition of the IP elements;

- compensation for the impact of disturbing factors;

- doubled signal conversion frequency;

- linearity of the amplitude and amplitude-frequency characteristics of the PI;

- the possibility of measurements without breaking the current lead circuit;

- minimizing the weight and dimensions of the IP.

IP with such characteristics allow to realize on their basis automated information-measuring systems of any level of complexity.

Information sources

1. Measuring transducer. RF patent №2176088, IPC G01R 19/00, 19/20, 01/11/2001.

Claims (1)

A measuring transducer comprising a transducer for measuring the amplitude of the measured current into a pulse voltage made on a ferromagnetic transformer in which the primary winding is connected in parallel with a segment of the measured current circuit, the magnetizing winding is connected to a magnetizing current source, the excitation winding is connected to the timing inputs of the pulse generator, and the compensation the winding is connected to the output of the negative feedback current amplifier, the input of which is connected to the current output of the demod an oscillator whose paraphase outputs are the outputs of the measuring transducer, characterized in that the generator output is connected to the input of the synchronizer and through the first and second standby multivibrators is connected to the corresponding inputs of the phase detector, the output of which is connected to the input of the demodulator, and the outputs of the synchronizer are connected respectively to the start and ban the operation of the generator.

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