SU1522116A1 - Instrument transducer of power - Google Patents

Abstract

The invention relates to information-measuring technology and can be used to measure the power of direct and pulsating currents, as well as the active power of single-phase alternating current. The purpose of the invention — improving accuracy and expanding functionality — is achieved by obtaining an output signal proportional to the power of the DC and pulsating currents in any combination of the polarities of the input signals, as well as the power of a single-phase AC. The converter contains measuring shunt 1, resistive divider 2, modulators 3 and 4, generator 5 of switching voltage, amplifiers 6 and 7 of alternating current, separation capacitors 8 and 9, inverting repeater 10 of alternating voltage, amplitude modulators 11 and 15, adders 12 and 16, the DC output filter amplifier 13, the source 14 of reference voltage, the integrator 17, the comparator 18 and the one-shot 19. The one-shot pulses can not be stabilized in duration, which greatly simplifies transformer. 4 sr. -l, 2 il.

Description

in

31

The invention relates to an information-measuring technique and can be used to measure the power of a constant and pulsating current, as well as the active power of a single-phase alternating current,

The purpose of the invention is to improve the accuracy and enhancement of the functionality by obtaining an output signal proportional to the power of the direct and pulsating current with any combination of polarities of the input signals, as well as the power of the single-phase alternating current.

In Fig. 1, "a functional diagram of the power transducer J in Fig. 2 is shown in time diagrams.

The converter contains measuring shunt 1, resistive divider 2, first and second modulators 3 and 4, switching voltage generator 5, first and second amplifiers 6 and 7 of alternating current, first and second isolating capacitors 8 and-9, inverting repeater 10 alternating voltages, first amplitude modulator 11, first adder 12, output filtering amplifier 13 for direct current, source 14 of standard alternating direct voltage, second amplitude modulator 15, second adder 16, integrator 17 for direct current comp The arator 18 and the single inverter 19, the outputs of measuring shunt 1 and resistive divider 2 are connected to the inputs of modulators 3 and 4, respectively, to the outputs of which, respectively, inputs of amplifiers 6 and 7 of AC are connected, controlling the inputs of modulators 3 and 4 are connected to outputs switching voltage generator 5, an output of an AC amplifier 6 through a coupling capacitor 8 is connected to the input of an inverting alternator 10 of an alternating voltage, the output of which is connected to the signal input of an amplitude modulator 11, the output of the amplitude modulator 11 and the input of the inverting alternator 10 alternating voltage are connected to the inputs of the first resistive adder 12, the output of which is connected to the input of the DC filter amplifier 13, the output of the alternating current amplifier 7 is connected to the first input

d 5

0 5 Q Q

0

A 164 house of resistive adder 16, a second input of a resistive adder 16 is connected to the first output of the source 14 reference alternating constant voltages, and the third to the output of the amplitude modulator 15, the signal input of which is connected to the second output of the source 14 reference differently polarized voltage, the output of the adder 16 is connected to the input of the integrator 17 of the direct current, the output of which is connected to the input of the comparator 18, the output of which is connected to the input of the one-oscillator 19, the output of which is connected to the control inputs of the amplitude mode tori 11 and 15. Each of the modulators comprises four key actuated 20-23 (24-27) connected in a bridge circuit.

The commutation voltage generator contains Schmidt trigger 28 and counting trigger 29.

The comparator and the one-shot comprise a trigger 30, an RS chain (31 and 32), and a control key 33.

The power converter operates as follows.

- The load current I, flowing through the measuring shunt 1, creates a voltage drop across its resistance R

Uu, i sh (1)

The voltage BSC is supplied to the input of the first constant voltage modulator 3 to the alternating voltage, the operation of which is controlled by the generator 5 of the switching voltage. The output AC voltage of the modulator 3, when the input current I is constant, has a rectangular shape with equal half-periods and an amplitude equal to iz, i.e.

UMI ± U t i RW. (2)

moreover, the plus or minus sign depends on the half-period of the switching voltage. The voltage And is amplified by the first variable voltage amplifier 6. The variable component Us, the output voltage U, through the coupling capacitor 8, which does not let the constant voltage go, and is fed to the input of the inverting repeater 10 of the alternating voltage, having the gain factor - 1. The output alternating voltage U and the repeater 10

and.

-U, + K, U, K ,, Ri, i, (3)

where K is the gain of the variable voltage amplifier 6.

 The input voltage U creates at the output of a resistive divider 2, consisting of resistors 34 (R,), 35 (R, the voltage Uj defined by the expression

Uj and R, / (R ,, + Il) KjU, (4)

where K 2 Ri / (Ri + R2) - coefficient

transmission divider 2.

The voltage Uj is modulated second

modulator 4, output voltage

 which is equal to

 ± tKjU (5)

The modulator 4 is controlled by a switching voltage generator. If the input voltage U is constant, i.e. does not contain higher harmonics, the voltage UMU as U, under the same condition, has & t rectangular shape with equal half periods. This voltage is amplified by a second AC amplifier 7, the decoded voltage U, of which contains a constant and a variable and “components”. The last, repeating shape of Uj ,, is passed by the coupling capacitor 9 to the first-INPUT of the resistive adder 16. Dn of this component we have

and 4 K 3 and + K 4K 3 and, (6)

where K- is the gain of the amplifier 7. The voltage is created because the integrator point a is. 17 DC is potentially grounded, in the resistor 36 (Rj) of the resistor adder 16 alternating current 3, equal to

i 3 3 ± К i К 3 and / Кз (7)

Through the resistor 37 (R4) of the adder 16, a constant current 1 flows from the output voltage U d to the source 14 reference alternating constant voltages. Let the voltage Ujini be negative. Current 14 equals

Uoni / R "const

(eight)

Resistor 37 is chosen such that the current IA exceeds Ij at

all possible values of the input voltage U.

Through the third resistor 38 (R) of the adder 16, no current flows if the amplitude modulator 15 connects this resistor to a common point of the circuit. This tact of the device will be called first.

In the second cycle, the amplitude modulator 15 connects the resistor 38 to a positive DC voltage generated by the source 14 reference voltage polarized voltages. A current of 1 flows through the resistor.

If SP

/ R

const

(9)

The resistor 38 is selected in such a way that the current if exceeds the sum of the currents 1d and T. for all possible values of the voltage, i.

llj I I i (10)

The resulting output current of the adder 1b is the input current of the integrator 17 of the direct current. During the first clock cycle, the voltage Un at the output of the integrator 17, the voltage, varies according to the law

i

Uv.t) U, c - s

i, dt

 U,

 Uo j. and

+ 1 (1h-and,) dt, (11)

0

where and, d is the voltage at the output of the integrator 17 at t 0. The increment of the voltage U, during the time t t, equal to the duration of the first cycle, is equal to

one

4 and

and 1

five

0

five

U / t) -U ", J. (ij + I,) dt (12)

 about . .

at t t, the voltage Uy reaches the operation level of the comparator 18. A pulse appearing at its output triggers the one-oscillator 19. The output voltage of the one-oscillator controls the operation of the amplitude modulator 15, which from this moment connects the resistor 38 to the voltage. Since inequality (10) is satisfied, the resultant output current 1 "of the adder 16, which is the input current of the integrator 17, changes its direction, as a result of which the output voltage and the" integrator 17 on, begins to decrease. Duration

the pulse produced by the one-shot rum 19 is determined by its parameters and is equal to .t ,. The change in voltage at the output of the integrator, whether ' over time t, is determined by analogy with (11) and (12) by

4U

AND 2

ipcuncjeiincpl,

I

   il (. ft

- ijj) dt

(13)

At the end of the pulse of the one-oscillator 19, the amplitude modulator 15 switches to the initial position, the input current of the integrator 1 takes the initial value 1 13 13 4 and the voltage at the output of the integrator 17 begins to increase again in accordance with expression (11). In the future, the processes in the scheme are repeated, and the period T of the operation of the scheme is equal

T t, + t "

(14)

The increment of the voltage U, during the first cycle 4 and 1 is equal to the decrease in dUni during the second. Equating (12) and (13), taking into account that

G 14 dt, I 15 dt 15 t,

bs one

And deciding on the frequency f -, we get

f 1 It + i-c.sr T 1 t

(13)

35

where 1sr -j -3 is the average value of 0,

The period of operation of the circuit is the value of the current ijSubstituted in (15) values, 1 ,, ig from (7) - (9) we find

f Uon-iRs + К Кз Rg in Uoni 4 and UoniRg -and

 fo ± f

(sixteen).

IV

where - J and dt average for the period

T work input voltage converter U, Uoni R5

 ° U ,,, RvtH

Ucp.

constant frequency component f

f KiKsRs „f. t; and-t-ucp

Upf, to j t,

variable is variable

g 0

five

0

five

five

0

The sign of f in formula (16) varies with the frequency f of the generator 5 of the switching voltage, and in the half-period when u4 K2 is negative, the directions of the currents ij and G coincide, and the frequency f increases (f in formula (16) has the plus sign), when the polarity changes and (i.e. in the other half period), the frequency t decreases (f in formula (16) has a minus sign). The parameters of the converter are chosen in such a way that the frequency f is much higher than the switching frequency i k, as well as the frequency of the highest frequency component in the input voltage curves U and current I,

Output variable voltage U. an inverting inverter 10 of an alternating voltage, having a frequency, is supplied to the signal input of an amplitude modulator 11, controlled by the output voltage of the one-oscillator 19. During the second cycle, i.e. when a pulse acts at the output of the one-shot 19, the amplitude modulator 11 connects the point ff to the output of the inverting alternator 10 of an alternating voltage, i.e. voltage at the point "Y - equals and. During the first cycle, the amplitude modulator 11 connects the point S to a common point, i.e. Uj P. Therefore, the voltage at point 5 is a sequence of pulses of duration tn with an amplitude equal to the value of U. at the corresponding points in time. For the case when the input voltage U and the current I are constant, and for the polarities of Fig.2, the time diagrams of the voltages U, (t), V (t), U4 (t) and Ur (t) are shown in figa-g.

As can be seen from Figure 2g, the constant component of the voltage U5 (t) during different half cycles of the switching voltage does not remain unchanged. In the first half-period (U (t) 70; Ua (t) -20, 11-4 (t) 0) f in the formula (16) there is a minus sign, so the frequency f

minimal (T j T) and constant constituting

and

ssr

  Wed 1 7 m WU n

55

 and 2 tn / Tmaks

negative and small (Fig. 2d). In the second half-cycle frequency f max

is maximal (T j T ,, „,

 - varnish

And the constant component is positive and equal to

   / T "" H UScf. (Fig.2d). Therefore, it is constant

the component voltage U | (t) for the period T of the switching voltage, as can be seen from FIG. 2d,

equals zero.

Find the value of U. The constant component for the period T of the output pulses of the one-shot 19 is equal to t tn

bsr t s t s t and

  S t, fu, cp (19) - 1

where 1 cf -j-) is the average of

-and time ty value of the voltage U.j (t).

Since the frequency f significantly exceeds the frequency of the highest-frequency harmonics of the input signals U and I, it can be assumed that during the time t U. U -j cf const and and iT Cf -U t, f. . ,, (20) where Ui is the instantaneous value of the voltage and,;, corresponding to the period under consideration T. Substituting in (20) the values of f from (16) and taking into account (3),.-We obtain

and

and

used

R5

and on a R + i KI Kz RS Ru.

U, and

about P a

.R.

(tU) (± i),

(21)

since, due to the smallness of T, we can also assume that Wed U

Choose T 1 (FIG. 2) equal to or integer times the period of the lowest frequency harmonic of the input signals U and I. Then the first term (21), proportional to the alternating voltage U, is also a variable voltage having -frequency commutation and constant component does not contain. If the input voltages and currents are constant, the first term is an alternating rectangular voltage with equal half-periods (voltages li $ in Fig.3, d). The product (iU) (± i) j included in the second term (21) is proportional to the instantaneous value P of the measured power, since the value is 52211610

Ki in front of Pi always changes simultaneously.

If the voltage U is applied to the filter amplifier 13 DC. the latter will suppress the first term, the variable component of the second, and highlight the constant component proportional to the average power P, i.e. measurable value

ten

Claims (1)

1G. i ui idt (22) However, the presence of the low-frequency first term in (21) requires a substantial increase in the time constant and decrease in the speed of the amplifier 13. With the help of adder 12, the first term (21) is fully compensated and does not pass to the input of the amplifier 13. Indeed, at the first input of the adder 12: a voltage is applied and, - And, This voltage creates a variable voltage at the input of the amplifier 13 II - 11 - 14 (23) D five 0 five where K "RJ // R, / RBV C R, R -, - resistance of resistors 39 and 40 adder 12, R ,, is the input resistance of the amplifier with Letter 13. The first term (21) creates a voltage at the input of the amplifier. IT - RS TT Rr and -, u / j r  -and,.  RT Uoni Rj- Rn (24) UodtR 4 R Since the voltages U and U have different signs, the condition of their full compensation is the equality of the modules of both voltages, equating (23) and (24) modulo, we obtain the condition of full compensation R-; Wom r g R Uj, naR4 (25) Therefore, the output voltage tiW (the current I gj,; () of the filter amplifier 13 of the direct current is proportional to the constant component (21) and is defined by the expression 1.  about tk  KS S uidt KS P, (26) where K is the constant conversion factor of the voltage component and. adder 12 and filter amplifier 13 Kj -K.) As can be seen from (26), the output voltage of the device is proportional to the power of the circuit being measured and does not depend on the duration t of pulses produced by the single-shot 19. Due to this, the single-vibration pulses can be not stabilized in duration, which greatly simplifies the converter. The duration of 1: „, as can be seen from (25), does not depend also on the condition of full compensation (25) to the variable component of the voltage Uj. Formula and goiter : 1. A POWER measuring transducer containing a measuring shunt connected in series with the load, a one-shot, first amplitude modulator, and a VDC DC filter amplifier, so that, in order to increase the accuracy and Expanding the FUNCTIONAL OPPORTUNITIES A resistive divider connected in parallel to the measured circuit is introduced into It, one of the output terminals of which is connected to the output of the measuring shunt. Two modulators, a switching voltage generator, two. AC amplifier, two coupling capacitors, inverting AC voltage follower, two adders, source of reference DC voltage, second amplitude .. modulator, integrator and comparator, with the input of the first amplitude modulator connected to the measuring the shunt, and the second input - to the output of the resistive divider, the outputs of the switching voltage generator are connected to the control inputs of the modulators, the input of the first and second AC amplifiers are connected to the outputs with corresponding modulators, the input of the inverting repeater of alternating voltage to the yarn through the first coupling capacitor is connected to the output of the first AC amplifier, and the output is connected to the signal input of the 50 5 0 0 d about 5 five the first input of the first resistive adder is connected to the input of an inverting repeater of an alternating voltage, the second input is connected to the output of a first amplitude modulator, and the output is connected to the input of an output DC filter amplifier, the first output of a source of reference polarized constant voltages zhenyi connected to the signal input of the second amplitude modulator, the first input of the second resistive adder through the second coupling capacitor is connected to the output of the second amplifier current, the second input is to the second output of the source of reference polarized DC voltages, and the third is to the output of the second amplitude voltage: -: a module, the output of the DC integrator is connected to the comparator input, the output of which is connected to the single input the vibrator, the input of the DC integrator is connected to the output of the second resistive adder, and the outputs of both amplitude modulators are connected to the output of the one-vibrator. ; 2, the converter according to claim 1, about a t; l and TSMJ that each of the modulators contains a controllable key connected to the bridge circuit, and the amplifiers of the alternating current are filled with a differential input. 3. The converter according to claim 1, wherein the switching voltage generator contains a Schmidt trigger and a trigger with a counting input connected to its output, whose codes are the outputs of the switching voltage generator. A, the converter according to claim 1, that is, that the comparator and the one-shot comprise an RS trigger, the installation input of which is connected to the output of the DC integrator, and an RS-circuit of the integrating type whose input is connected to the forward output of the trigger, which is the output of the one-shot, and the output is connected to the input of the installation in the O trigger, and parallel to the RS circuit capacitor is connected a forward key and the control input of which is connected to the trigger output in such a way that with a single trigger state, the key is open. 131522116. 1 5. The converter according to p. 1, about the t-current of the current is made with galvanic, characterized by the fact that the output is the separation of the input and output circuits, the filter amplifier is constant and one } g / g Uffcpl FIG. 2