RU2183044C1 - Single-phase-to-multiphase signal converter - Google Patents

Abstract

FIELD: electric measurement technology. SUBSTANCE: converter built around phase-shifting RC circuit is provided, in addition, with voltage followers built around operational amplifiers used for isolating RC circuits to reduce equivalent time constant of converter. EFFECT: enhanced speed of device. 2 cl, 3 dwg

Description

 The invention relates to electrical engineering, in particular to converters of a single-phase signal to multiphase.

 The simplest single-phase to multiphase (two-phase) signal converter is the well-known induction voltage transformer with antiphase switching of the windings. The disadvantage of this device is the small number of phases of the output signal.

 The closest in technical essence to the proposed one is a single-phase to multi-phase signal converter based on a phase splitter, which is assembled on several RC circuits (see Volgin L.I. Measuring converters of alternating voltage to constant. M: "Sov. Radio", 1977, p. 86, Fig. 2.52). Such a device is taken as a prototype. Using it, you can increase the number of phases, but it contains inertial elements (capacitors), therefore, with an increase in the number of phases, the equivalent time constant increases, which leads to a decrease in the speed of the converter.

 The technical result is an increase in speed of the Converter.

 The specified technical result is achieved in that in the known converter of a single-phase signal into a multiphase, containing a voltage transformer with primary and secondary windings, the first, second, third and fourth resistors, the first, second, third and fourth capacitors, the first capacitor and the first resistor, the second a capacitor and a second resistor, a third resistor and a third capacitor, a fourth resistor and a fourth capacitor are connected in series, respectively, the first terminal of the secondary winding of the transformer is inen with other terminals of the second capacitor and fourth resistor, the second terminal of the secondary winding of the transformer is connected to other terminals of the first resistor and third capacitor, the middle point of the secondary winding of the transformer is connected to the ground bus, the outputs of the converter are the conclusions of the secondary winding of the transformer, as well as the common connection points respectively of the first a capacitor and a first resistor, a second capacitor and a second resistor, a third resistor and a third capacitor, a fourth resistor and of the second capacitor, the peculiarity lies in the fact that four voltage followers based on operational amplifiers are introduced into the converter, the first output of the secondary winding of the transformer through the first follower connected to another output of the first capacitor and through the second follower to the other output of the third resistor, the second output of the secondary winding transformer through the third repeater is connected to another terminal of the second resistor and through the fourth repeater to another terminal of the fourth capacitor.

 The analysis of the prior art made it possible to establish that the applicant has not found an analogue characterized by features identical to all the features of the claimed invention, and the determination from the list of analogues of the prototype made it possible to identify a set of distinctive features that are perceived by the applicant as the technical result of the claimed device set forth in the claims. Therefore, the claimed invention meets the condition of "novelty."

 To verify compliance of the claimed invention with the condition "inventive step", the applicant conducted an additional search for known solutions in order to identify signs that match the distinctive features of the claimed device from the prototype. The search results showed that the claimed invention does not follow explicitly from the prior art for the specialist, since the influence of the transformations provided for by the essential features of the claimed invention on the achievement of the technical result is not revealed from the prior art determined by the applicant. Therefore, the claimed invention meets the condition of "inventive step".

 The drawings show: FIG. 1 shows two phase shifters connected in parallel; figure 2 shows the curves of the transition process; figure 3 shows a diagram of the proposed device.

 The Converter (figure 3) contains a voltage transformer 1, a first capacitor 2, a first resistor 3, a second capacitor 4, a second resistor 5, a third capacitor 6, a third resistor 7, a fourth capacitor 8, a fourth resistor 9, a first 10, a second 11, a third 12, fourth 13 voltage followers. The outputs of the device are conclusions 14.

 The operation of the Converter is as follows.

 The voltage from the secondary winding of the transformer 1 is supplied to the RC circuits (phase shifters) formed by resistors 3, 5, 7, 9 and capacitors 2, 4, 6, 8. These circuits create positive and negative phase shifts relative to the input voltage. The output voltages of transformer 1 and each RC circuit are the output voltages of the converters, which are removed relative to the ground bus.

 In the prototype, all phase shifters are connected in parallel, so the equivalent time constant of such a device increases, which can be shown by the example of two phase shifters (connected in parallel) when a transient occurs (Fig. 1).

а второго

Тогда эквивалентное сопротивление

и характеристическое уравнение в этом случае имеет два корня:
p₁=-R₁C₁; p₂=-R₂C₂ (4)
а переходный процесс описывается суммой двух экспонент (для тока i, фиг. 1):
i=A₁e^P1t+A₂e^P2t (5)
что показано на фиг.2 (кривая 1). При наличии же только одного фазовращателя переходный процесс описывается одной экспонентой (кривые 2 и 3 на фиг.2):
i₁=A₁e^P1t или i₂=A₂e^P2t (6)
Длительность суммарной экспоненты (5) практически совпадает с длительностью одной из экспонент (6), но, если оценивать влияние переходного процесса, например, по среднему значению экспоненциальной составляющей, то в первом случае (при наличии двух параллельных фазовращателей) это влияние будет более значительным, поскольку амплитуда суммарной экспоненты выше. Этот факт можно расценивать как возрастание эквивалентной постоянной времени при увеличении количества параллельно соединенных фазовращателей.Let the resistance of the first phase shifter in operator form

and second

Then the equivalent resistance

and the characteristic equation in this case has two roots:
p ₁ = —R ₁ C ₁ ; p ₂ = -R ₂ C ₂ (4)
and the transient is described by the sum of two exponentials (for current i, Fig. 1):
i = A ₁ e ^P1t + A ₂ e ^P2t (5)
as shown in figure 2 (curve 1). If there is only one phase shifter, the transition process is described by one exponent (curves 2 and 3 in figure 2):
i ₁ = A ₁ e ^P1t or i ₂ = A ₂ e ^P2t (6)
The duration of the total exponent (5) practically coincides with the duration of one of the exponentials (6), but if we evaluate the influence of the transient process, for example, by the average value of the exponential component, then in the first case (in the presence of two parallel phase shifters) this effect will be more significant, since the amplitude of the total exponent is higher. This fact can be regarded as an increase in the equivalent time constant with an increase in the number of phase shifters connected in parallel.

 To eliminate this drawback, an “isolation” of RC circuits is proposed using voltage repeaters 10-13 (FIG. 3), which can be made on the basis of operational amplifiers (op amps) having a large input and low output impedance. In this case, the transition process (when it occurs) occurs separately in each circuit, including transformer 1, one of the voltage followers (10; 1 1; 12; 13), one of the RC circuits (2-3; 4-5; 7 -6; 8-9). Therefore, in connection with the foregoing, the amplitude of the exponential component of the transition process decreases, i.e. the transition effect decreases, which can be regarded as an increase in the speed of the Converter compared with the prototype. Moreover, the above example is shown with two phase shifters, and with an increase in the number of the latter, the effectiveness of the proposed solution increases.

(7)
где К - коэффициент усиления ОУ на низких частотах; f₁- частота единичного усиления. Например, для ОУ типа К 140 УД 6 τ_ОУ≈ 0,008 с (при К=50000 и f₁=1 мГц).It is necessary to raise the issue of the influence of the time constant of voltage followers 10-13. For an open op-amp, the time constant can be found from the expression (see Gutnikov BC Integrated Electronics in Measuring Devices. -L.: Energoatomizdat, 1988. - P. 26):

(7)
where K is the gain of the op-amp at low frequencies; f ₁ is the frequency of unity gain. For example, for an op-amp of type K 140 UD 6 τ, an _{op-amp is} ≈ 0.008 s (at K = 50,000 and f ₁ = 1 MHz).

When the opamp is covered by negative feedback, its time constant decreases (Kβ + 1) times, where Kβ is the loop gain. For the voltage follower β = 1, therefore, it decreases by a factor of K. For example, for an op amp of type K 140 UD 6 τ, an _{op amp is} ≈ 1.6 • 10 ^-7 s, i.e. is of very little importance. Therefore, if we choose the time constants of RC chains much larger than the time constant of the repeater (which is not difficult), then the latter will not affect the duration of the transient process.

 Thus, for the claimed device in the form as described in the claims below, the possibility of its implementation using the means described in the application is confirmed. Also, a device embodying the claimed invention in its implementation is capable of achieving the achievement of the technical result perceived by the applicant.

 Therefore, the claimed invention meets the condition of "industrial applicability".

Claims (1)

 A single-phase to multi-phase signal converter comprising a voltage transformer with primary and secondary windings, first, second, third and fourth resistors, first, second, third and fourth capacitors, the first capacitor and first resistor, the second capacitor and second resistor, the third resistor and third the capacitor, the fourth resistor and the fourth capacitor are connected in series, respectively, the first terminal of the secondary winding of the transformer is connected to other terminals of the second capacitor and the fourth resistor ora, the second terminal of the secondary winding of the transformer is connected to other terminals of the first resistor and the third capacitor, the middle point of the secondary winding of the transformer is connected to the ground bus, the outputs of the converter are the terminals of the secondary winding of the transformer, as well as the common connection points of the first capacitor and first resistor, second capacitor, and a second resistor, a third resistor and a third capacitor, a fourth resistor and a fourth capacitor, characterized in that in the converter four voltage followers based on operational amplifiers are installed, the first terminal of the secondary winding of the transformer through the first follower connected to the other output of the first capacitor and through the second follower to the other output of the third resistor, the second output of the secondary winding of the transformer through the third follower connected to the other output of the second resistor and through the fourth repeater - with another terminal of the fourth capacitor.

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