RU163965U1 - DEVICE FOR MEASURING THE ACTUAL VALUE OF VARIABLE VOLTAGE - Google Patents

Abstract

1. A device for measuring the rms value of an alternating voltage, comprising a first quadrator, a comparator, a frequency-voltage converter and a square root extraction unit, the output of which is the output of the device, the input of which is connected to the input of the first quadrator and the input of the comparator, the output of which is connected to the input of the frequency converter voltage, characterized in that it additionally introduced a controlled phase shifter, a second quadrator, an adder and a hyperbolic converter, and the input of the device with dinene with the input of the controlled phase shifter, the output of which is connected to the input of the second quadrator, the outputs of the first and second quadrators are connected respectively to the first and second inputs of the adder, the output of which is connected to the input of the square root extraction unit, and the output of the frequency-voltage converter is connected to the input of the hyperbolic converter, the output of which is connected to the control input of the controlled phase shifter. 2. A device for measuring the effective value of an alternating voltage according to claim 1, characterized in that the controlled phase shifter comprises an operational amplifier, two resistors, a field effect transistor and a capacitor, the first terminals of the first and second resistors connected to the inverting input of the operational amplifier, the output of which is connected to the second terminal the second resistor and the output of the controlled phase shifter, the input of which is connected to the second output of the first resistor and the drain of the field effect transistor, the source of which is connected to non-inv rtiruyuschim input of the operational amplifier and the first terminal of the capacitor, the second terminal of which is connected

Description

The utility model relates to electrical engineering, and can be used to measure AC voltage by converting it to DC in a wide range of frequencies.

A device is known that calculates the rms value of an alternating voltage, consisting of a series-connected quadrator, integrator and square root extraction circuit [Timonteev V.N., Velichko L.M., Tkachenko V.A. Analog signal multipliers in electronic equipment. - M .: Radio and communications, 1982. - p. 73, fig. 4.31].

The disadvantage of this device is the constant time constant of the integrator for various frequencies of the measured voltage. So, to ensure the required accuracy, the integration time constant is chosen much longer than the period of the lower frequency of the input signal of the operating frequency range, which leads to a significant decrease in the measurement speed.

The closest analogue to the proposed utility model is a device for measuring the effective value of an alternating voltage [USSR Author's Certificate No. 1712892 IPC ⁸ G01R 19/02, publ. 01/25/1990], a device for measuring the rms value of an alternating voltage, comprising a quadrator connected in series, an integrator with a constant-voltage constant-voltage integration, a comparator, a frequency-to-voltage converter and a square root extractor, the output of which is the output of the device, the input of the quadrator is the input of the device the output of which is connected to the control input of the integrator, and the input is connected to the output of a comparator, the input of which is connected to the input of the quadrator, and the integrator contains a field-effect transistor and a capacitor, the first terminal of which is connected to the common bus, and the second terminal is the output of the integrator and connected to the drain of the field-effect transistor, whose source is the input of the integrator, and the gate is the control input of the integrator.

This technical solution is selected as a prototype.

The tunable time constant of the integrator allows to increase the speed of the device compared to the analogue, however, the device does not have a high speed and accuracy of voltage measurement, especially at the lower frequencies of the operating range, due to the presence of an integrator in the DC signal path.

The technical result of the claimed utility model is to increase the speed and accuracy of voltage measurement due to the absence of an integrator in the device.

The specified technical result is achieved by the fact that in a known device for measuring the effective value of the alternating voltage, comprising a first quadrator, a comparator, a frequency-voltage converter and a square root extraction unit, the output of which is the output of the device, the input of which is connected to the input of the first quadrator and the input of the comparator, the output of which is connected to the input of the frequency-voltage converter, a controlled phase shifter, a second quadrator, an adder and a hyperbolic converter are additionally introduced a caller, the input of the device being connected to the input of a controlled phase shifter, the output of which is connected to the input of the second quadrator, the outputs of the first and second quadrators are connected respectively to the first and second inputs of the adder, the output of which is connected to the input of the square root extraction unit, and the output of the frequency-voltage converter is connected with the input of the hyperbolic converter, the output of which is connected to the control input of the controlled phase shifter. The controlled phase shifter contains an operational amplifier, two resistors, a field effect transistor and a capacitor, the first outputs of the first and second resistors connected to the inverting input of the operational amplifier, the output of which is connected to the second output of the second resistor and the output of the controlled phase shifter, the input of which is connected to the second output of the first resistor and the drain of the field effect transistor, the source of which is connected to the non-inverting input of the operational amplifier and the first output of the capacitor, the second output of which is It is connected to the bus of zero potential, and the gate of the field-effect transistor is connected to the control input of the controlled phase shifter.

Significant differences of the proposed device are the introduction of a controlled phase shifter, second quadrator, adder and hyperbolic transducer, as well as a new organization of relations between the elements of the device. The combination of elements and the relationships between them ensure the achievement of a positive effect - improving the speed and accuracy of the device.

The essence of the utility model is illustrated by drawings. In FIG. 1 shows a functional diagram of the device, in FIG. 2 is a diagram of a controlled phase shifter, in FIG. 3 - time diagrams of voltages u _in , u ₁ -u ₃ , u ₆ and u _out .

The device (Fig. 1) contains quadrants 1, 6, a comparator 2, a frequency-voltage converter 3, a square root extraction unit 4, a controllable phase shifter 5, an adder 7, and a hyperbolic converter 8.

The comparator 2 is designed to generate a rectangular voltage u ₅ from the input sinusoidal voltage u _I. The frequency-voltage Converter 3 converts the frequency of the input signal ω into a voltage u ₆ DC of positive polarity, proportional to the frequency ω. Hyperbolic transducer 8 generates at its output a voltage u ₇ inversely proportional to its input u ₆ .

The controlled phase shifter 5 (Fig. 2) contains an operational amplifier 9, two resistors 10, 11, a field effect transistor 12, and a capacitor 13.

The controlled phase shifter 5 is designed to phase shift the input signal by an angle of 90 ° in the operating frequency range at a unity gain. To do this, it is necessary to maintain the following relationships between the components of its circuit:

R ₁₀ = R ₁₁ ; R _t = 1 / (ωС ₁₃ ),

where R _t is the resistance of the field effect transistor;

ω is the circular frequency of the input voltage.

The device operates as follows. The measured AC voltage u is applied to the inputs _Rin squarer managed fazosmeschatelya 1 and 5, the output of which is formed by a voltage equal in amplitude and shifted in phase relative to u _Rin by an angle φ = 90 ° to the advance side (FIG. 3).

The inputs of quadrants 1, 6 receive respectively the voltages u _in and u ₁ , the same in amplitude and phase-shifted relative to each other by an angle φ = 90 °:

u _in = U _{m in} sin sint, u ₁ = U _{m in} sin (ωt + 90 °) = U _{m in} cos ωt,

where U _{m I} - the amplitude of the measured input voltage.

At the outputs of the quadrants 1, 6, antiphase voltages u ₂ , u _{3 are formed} , obtained after squaring the voltages u _in and u ₁ :

;

.

;

.

After summing the voltages u ₂ , u ₃ in the adder 7 and the transformations, at its output we have the voltage u ₄ (Fig. 3):

.

.

After the operation of extracting the square root in the block extracting the square root 4 at the output of the device, the voltage u _{output is formed} :

.

.

Thus, the output constant voltage u of the _output device does not contain a variable component, and its value is equal to the amplitude of the measured input voltage U _{m in} , that is, in proportion to the effective value of u _in .

In order for the voltages u ₂ , u ₃ at the outputs of the quadrants 1, 6 to be out of phase in a wide frequency range, it is necessary to constantly maintain the phase angle φ between voltages u _in and u ₁ equal to 90 ° regardless of the frequency of the measured voltage. This purpose is served by a controlled phase shifter 5 having a control input, to which voltage u ₇ is supplied from the output of a hyperbolic transducer 8, which is formed from the output voltage u _{6 of} the frequency-voltage converter 3 proportional to the frequency ω of the input voltage u _in and is determined by the expression:

u ₇ = 1 / (K ₁ ω),

where K ₁ is the transfer coefficient of the frequency-voltage converter 3.

The voltage u ₇ is supplied to the control input of the controlled phase shifter 5 and changes the resistance of the field-effect transistor 12 inversely proportional to the frequency ω. In this case, the phase angle φ of the voltages of the controlled phase shifter 5, defined by the expression

φ = π-2arctg (ωC ₁₃ R _t ) = π-2arctg (ωC ₁₃ R _t0 / K ₁ ω) = π-2arctg (C ₁₃ R _t0 / K ₁ )

independent of the frequency ω of the input voltage. In this expression, R _t0 is the resistance of the field-effect transistor 12 with a control voltage u ₇ at the gate equal to zero.

Frequency-to-voltage converter 3 transmission coefficient K ₁ is selected by the expression:

K ₁ = C ₁₃ R _t0 .

In this case, the phase angle φ between the voltages u _in and u _{1 of the} controlled phase shifter 5 will always be 90 °.

Due to the automatic change in the resistance of the field-effect transistor 12 inversely proportional to the frequency of the input voltage ω, the phase angle φ is kept constant throughout the operating frequency range of the input voltage and equal to 90 °, and the output constant voltage u of the _output device does not contain a variable component.

Thus, due to the lack of an integrator in the proposed utility model, an increase in speed and accuracy of voltage measurement is provided.

In the practical implementation of the proposed device, minor ripple of the output voltage due to distortions in the shape of the sinusoidal voltage and inaccuracies in the tuning of the controlled phase shifter 5 can be eliminated by turning on the low-pass filter with a small time constant after the adder 7, which will not significantly affect the speed of the device.

When constructing quadrants 1, 6 and hyperbolic transducer 8, you can use voltage multipliers on the KR525PS3 microcircuit. The adder 7 is a conventional adder on an operational amplifier. As a unit for extracting the square root 4, you can use the circuit on the operational amplifier, including a quad in the circuit of its negative feedback. Field-effect transistor 12 with an n-type pn junction control can be selected as KP302B type. As a frequency-voltage converter, you can use a converter on the KR1108PP1 chip.

Claims (2)

1. A device for measuring the rms value of an alternating voltage, comprising a first quadrator, a comparator, a frequency-voltage converter and a square root extraction unit, the output of which is the output of the device, the input of which is connected to the input of the first quadrator and the input of the comparator, the output of which is connected to the input of the frequency converter voltage, characterized in that it additionally introduced a controlled phase shifter, a second quadrator, an adder and a hyperbolic converter, and the input of the device with dinene with the input of the controlled phase shifter, the output of which is connected to the input of the second quadrator, the outputs of the first and second quadrators are connected respectively to the first and second inputs of the adder, the output of which is connected to the input of the square root extraction unit, and the output of the frequency-voltage converter is connected to the input of the hyperbolic converter, the output of which is connected to the control input of the controlled phase shifter. 2. A device for measuring the rms value of an alternating voltage according to claim 1, characterized in that the controllable phase shifter comprises an operational amplifier, two resistors, a field effect transistor and a capacitor, the first terminals of the first and second resistors being connected to the inverting input of the operational amplifier, the output of which is connected to the second terminal of the second resistor and the output of the controlled phase shifter, the input of which is connected to the second terminal of the first resistor and the drain of the field-effect transistor, the source of which is connected to non- by the vertical input of the operational amplifier and the first output of the capacitor, the second output of which is connected to the zero potential bus, and the gate of the field-effect transistor is connected to the control input of the controlled phase shifter.

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