CA1238686A - Method and device for measuring an electric quantity average value related to a series of periodic wave trains - Google Patents
Method and device for measuring an electric quantity average value related to a series of periodic wave trainsInfo
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- CA1238686A CA1238686A CA000479851A CA479851A CA1238686A CA 1238686 A CA1238686 A CA 1238686A CA 000479851 A CA000479851 A CA 000479851A CA 479851 A CA479851 A CA 479851A CA 1238686 A CA1238686 A CA 1238686A
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Abstract
ABSTRACT OF THE DISCLOSURE:
A method and a device for measuring an electric quan-tity average value related to a series of trains of a periodic wave, which wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive time intervals. The mea-suring device comprises a circuit for measuring the elec-tric quantity related to the wave train produced during each time interval considering that the wave train is ininterrupted.
A storage circuit memorizes the so measured electric quantity.
An impulse is produced in response to each complete period of the periodic wave in each wave train. A first memory counts the number of impulses of the wave train of each odd time interval, multiplies the so counted impulses with the measured electric quantity related to the wave train of the odd interval to produce a multiplied value delivered on an output as the electric quantity average value during the one of the time intervals immediately following the odd interval.
A second memory counts the number of complete periods in the wave train produced during each even time interval, multi-plies the so counted periods with the measured electric quantity related to the train of the same, even interval to produce a multiplied value delivered on the output as the electric quantity average value during the time interval immediately following the even one.
A method and a device for measuring an electric quan-tity average value related to a series of trains of a periodic wave, which wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive time intervals. The mea-suring device comprises a circuit for measuring the elec-tric quantity related to the wave train produced during each time interval considering that the wave train is ininterrupted.
A storage circuit memorizes the so measured electric quantity.
An impulse is produced in response to each complete period of the periodic wave in each wave train. A first memory counts the number of impulses of the wave train of each odd time interval, multiplies the so counted impulses with the measured electric quantity related to the wave train of the odd interval to produce a multiplied value delivered on an output as the electric quantity average value during the one of the time intervals immediately following the odd interval.
A second memory counts the number of complete periods in the wave train produced during each even time interval, multi-plies the so counted periods with the measured electric quantity related to the train of the same, even interval to produce a multiplied value delivered on the output as the electric quantity average value during the time interval immediately following the even one.
Description
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The invention relates to a method and device sui-table for measuring an average value of the effective voltage and of the electric power supplied to a three phase electric load of polyphase variators with commutation to zero voltage.
Devices or converters of the above type are employed to measure an average value of the electric power or of the effective voltage supplied to a load for wave shapes consist-ing of trains of wave having a variable number of complete periods of the supply voltage.
]0 In order to measure these values, converters with thermal effect can be used. Their disadvantages are that compensation measures of ambient temperature variation are needed and they do not provide any indication for very low frequencies.
There are also known a method and device for measu-ring the average power in AC. The method consists in mea-suring the products between the voltage, current and power factor of each phase, the signal converted into voltage then being converted into frequency and conditionally transmitted to the output by tact impulses. The device includes three current multipliers responsive to the voltage of each phase, foll~
by a counter, then a recording system with a frequency-voltage converter, and a circuit consisting of AND-gates controlled by a multi-stage generator with nondecaying sto-rage.
These device and method have the disadvantage of being nonutilizable in the case of alternating voltage shaped as trains of waves with a variable number of periods.
According to the present invention, there is provided a method of measuring an electric quantity average value related to a series of trains of a periodic wave, said wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive time intervals, which method comprises the steps of:
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(a) measuring the electric quantity related to the wave train produced during a first one of the time intervals considering that the wave train is ininterrupted;
(b) measuring the number of complete periods of the periodic wave in the wave train produced during the first time interval;
(c) multiplying the electric quantity measured in step (a) with the wave period number measured in step (b) in order to produce a first multiplied value;
(d) storing the flrst multiplied value in a fi.rst memory means;
(e) delivering on an output the first multiplied value stored in the first memory means as the electric quan-tity average value during a second one of the successive time intervalsfollowing the first timeinterval;
(f) measuring the electric quantity related to the wave train produced during the second time intervalconsidering that the wave train is ininterrupted;
(g) measuring the number of complete periods of the periodic wave in the wave train produced during the second time interval;
(h) multiplying the electric quantity measured in step (f~ with the wave period number measured in step (g) in order to produce a second multiplied value;
(i) storing the second multiplied value in a second memory means;
(j) delivering on the output the second multiplied value stored in the second memory means as the electric quan-tity average value during a third one of the successive time intervals following the second time interval; and (k) repeating the above steps (a) to (j) during the subsequent ones of the successive time intervals starting from the third time interval.
In accordance with the invention, there is also provided
The invention relates to a method and device sui-table for measuring an average value of the effective voltage and of the electric power supplied to a three phase electric load of polyphase variators with commutation to zero voltage.
Devices or converters of the above type are employed to measure an average value of the electric power or of the effective voltage supplied to a load for wave shapes consist-ing of trains of wave having a variable number of complete periods of the supply voltage.
]0 In order to measure these values, converters with thermal effect can be used. Their disadvantages are that compensation measures of ambient temperature variation are needed and they do not provide any indication for very low frequencies.
There are also known a method and device for measu-ring the average power in AC. The method consists in mea-suring the products between the voltage, current and power factor of each phase, the signal converted into voltage then being converted into frequency and conditionally transmitted to the output by tact impulses. The device includes three current multipliers responsive to the voltage of each phase, foll~
by a counter, then a recording system with a frequency-voltage converter, and a circuit consisting of AND-gates controlled by a multi-stage generator with nondecaying sto-rage.
These device and method have the disadvantage of being nonutilizable in the case of alternating voltage shaped as trains of waves with a variable number of periods.
According to the present invention, there is provided a method of measuring an electric quantity average value related to a series of trains of a periodic wave, said wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive time intervals, which method comprises the steps of:
~3~
(a) measuring the electric quantity related to the wave train produced during a first one of the time intervals considering that the wave train is ininterrupted;
(b) measuring the number of complete periods of the periodic wave in the wave train produced during the first time interval;
(c) multiplying the electric quantity measured in step (a) with the wave period number measured in step (b) in order to produce a first multiplied value;
(d) storing the flrst multiplied value in a fi.rst memory means;
(e) delivering on an output the first multiplied value stored in the first memory means as the electric quan-tity average value during a second one of the successive time intervalsfollowing the first timeinterval;
(f) measuring the electric quantity related to the wave train produced during the second time intervalconsidering that the wave train is ininterrupted;
(g) measuring the number of complete periods of the periodic wave in the wave train produced during the second time interval;
(h) multiplying the electric quantity measured in step (f~ with the wave period number measured in step (g) in order to produce a second multiplied value;
(i) storing the second multiplied value in a second memory means;
(j) delivering on the output the second multiplied value stored in the second memory means as the electric quan-tity average value during a third one of the successive time intervals following the second time interval; and (k) repeating the above steps (a) to (j) during the subsequent ones of the successive time intervals starting from the third time interval.
In accordance with the invention, there is also provided
2 -, . . .
~23~ 1!36 a device for measuring an electric quantity average value related to a series of trains of a periodic wave, these wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive timeintervals, which measuring device com-prising:
means for measuring said electric quantity of the wave train produced during each of the intervalsconsidering that said wave train is ininterrupted, which measuring means comprises means for producing an electric quantity measure signal during each of the time intervals;
means for storing the electric quantity measure signal produced during each time interval;
means for producing a first impulse at the beginning of each wave train, and for producing second impulses repre-sentative of the number of complete periods of the periodic wave in each wave train;
first memory means comprising:(a) first means for counting the second impulses representative of the num~er of complete periods in the wave train produced during each of the odd ones of the successive time intervals and for producing a count value representative of the number of second impulses counted during the odd interval; (b) first means for multiplying the count value produced during the odd time intervalwith the stored electric quantity measure signal produced during the one of said intervals immediately following said odd interval in order to generate a first multiplied signal; (c) first means for storing the first multiplied signal; and ~d) first means responsive to the first impulses for supplying on an output of the measuring device the stored, first mul-tiplied signal as the electric quantity average value duringthe one of the time intervals immediately following the odd interval; and second memory means including:(a) second means for counting the second impulses representative of the number of ,. ':: ' : .~ : :
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complete periods in the wave train produced during each of the even ones of the successive time intervals and for producin~
a count value representative of the number of second impulses counted during the even interval; (b) second means for multi-plying the count value produced during the even time intervalwith said stored electric quantity measure signal produced during the one of said time intervals immediately following said even interval in order to generate a second multiplied signal; (c) second means for storing the second multiplied signal; and (d) second means responsive to the Eirst impulses for supplying on the output of the measuring device the stored, second multi-plied signal as the electric quantity average value during the one of the successive time intervals immediately following the even interval.
The periodic wave may be an alternating voltage and the electric quantity the effective value of this alternating voltage. The periodic wave may also be formed by alternating current and voltage and the electric quantity by the electric power supplied to a load. The periodic wave may further be a three phase alternating voltage and the electric quantity the effective value of this three phase voltage. The periodic wave may still further be formed by three phase alternating current and voltage, and the electric quantity by the three phase electric power supplied to a load.
In accordance with a preferred embodiment of the inven-tion, in which the periodic wave is an alternating voltage ap-plied to a load and the electric quantity the effective voltage supplied to this load, the square of the effective voltage re-lated to the train in each time interval is measured considering a continuous supply of the load with alternating voltage, the so measured square of the effective voltage is multiplied with the number of complete periods of the periodic wave in the same wave train to produce the corresponding multiplied signal or value, and the first and second multiplied si-gnals or values are square-rooted before being delivered ~38g~l36 on the ou-tput as the electric quantity average value~
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non restrictive description of two examples of carrying out the same, given with reference to the accom-panying drawings, in which:
Figure l illustrates measurement, in accordance with the invention, of an average value of the electric power sup-plied to a load; and Figure 2 shows measurement, inaccordance with the present invention,of an average value of the efective vol-tage supplied to the load.
The average values of the electric power or of the effective voltage supplied to the load for waveforms, consis-ting of trains of wave having a variable number of complete periods of the supply voltage, are given by the following expresslons:
P k 1 ~ uidt n (1) Usef Uef ~ ~ Uef n (2) where: PS is the average value of the electric power supplied to the load;
k is the number of the complete wave periods in the train;
n is the maximal number of complete voltage wave pe-riods in a cyclic basic time interval Tk;
P is the power, for example the average or apparent power consi-dering a continuous supply oE the load by the supply networkoperating at a frequency f = 50 Hz (60 Hz);
u and i are respectively the instantaneous values of the voltage and current supplied to the load;
dt indicates derivative with respect to time;
T is the cyclic basis time interval;
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Usef is the average value of the effective voltage supplied to the load; and ~ ef is the effective voltage supplied to the load considering a continuous supply of the load with voltage from the supply network (k = n).
The electric power P is measured during the first vol-taye and current wave period applied to the load within the first Tk of successive time intervals and it is multiplied by an analog value given by a digital-to-analog converter of the real number k of voltage and load current wave periods.
A memory Ml stores the result of the multiplication represen-ting PS during the complete interval Tk,and a switching circuit transfers the value PS at the output of the measuring device at the beginning of the intervalTk+l; in the time interval Tk+l the value of Ps~ corresponding to number k + 1 of voltage and current wave periods controlled on the load, is measured again and it is stored in another memory M2, and it is trans-mitted by a switching circuit on the output of the device at the beginning of the intervalTkf2, concomitantly with the erasing of the memory Ml prepared to measure the power PS
for the interval Tk+2.
In order to measure the average value of the effective voltage supplied to a load the same circuit structure as that pre-viously described is used, but during the first alternations of each interval Tk, Tk+l the value Uef is measured, and the out-put of the device is applied to an analog square-rooting circuit according to relation 2.
As shown in Figure 1, in order to measure the apparent power P, several multiplying circuits 1,2,3 multiply the star /phase voltages UR, Us, UT with the phase currents IR, Is, IT, respectively. The signals produced at the output of the multiplying circuits l, 2 and 3 are respectively supplied to the inputs of the integrating circuits 4,5,6 having their outputs connected to three inputs of a summator 7 which produces .'.'`
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an analog signal, proportional to P at its output. This si-gnal is applied to a first input of a comparator 8.
An oscjllator 9 generates impulses applied to a gate circuit 10 controlling a binary counter 11. The outputs of the counter 11 are connected to the inputs of a digital-to-analog converter 12, which converter 12 has an output con-nected to a second input of the comparator 8.
The output of the comparator 8 is applied to a second input of the gate circuit 10 and s*ops -the transmission of impulses to the counter 11, when the value of the voltage at the output of the converter 12 is equal to the amplitude of the signal delivered from the summator circuit 7, thus achieving storage of the measured information P.
The measuring cycle begins all over again at the end of eachinterval Tk by erasing the counter 11 through first impulses generated at the beginning of each wave train.
The analog signal P produced by the converter 12 re-presents the reference voltage for a pair of digital-to-analog converters 13, 14 which have a multiplying function. A flip-flop sweep switching circuit 15r controlled by second impulses generated in response to each period of the voltage applied to the load, controls the circuits of the memory M1 made up of a gate circuit 16, a binary counter 17, a commutating transistor 18 and the digital-to-analog converter 13.
The digital-to-analog converter 13 produces an output voltage representative of the value resulting from the multi-plication of P given by the converter 12, and the analog con-verted value of the wave number k supplied to the load given by the counter 17, which value expresses the value Ps~
The memory M2 similarly to the memory M1 consists of a gate circuit 19, a binary counter 20, a commutating transis-tor 21 and the digital-to-analog converter 14.
In response to the first impulse generated at the beginning of each odd interval such as Tk, the circuit 15 generates on its first input ~:3~ 36 a high logic level signal which turns the transistor 18 on and causes the output voltage of the converter 13 to drop to zero, while resetting the binary counter 17 and closing the gate circuit 16 to allow transmission of the second impulses representative of the number of complete periods of the wave train in the interval Tk toward the binary counter which counts the same. During this time, the circuit 15 generates on its second input a low logic level signal which turns the transis-tor 21 off to allow transmission of the output voltage from the converter 14 to the output of the measuring device, and which opens the gate circuit 19 to block the second impulses.
In response to the first impulse generated at the beginning of each even interval such as Tk+l, the circuit 15 generates on its first output a low logic level signal which turns the transistor 18 off whereby the output signal from the converter 13 is supplied to the output of the measuring device and the gate circuit 16 opened to stop the second impulses.
During this time, the circuit 15 also supplies on its second output a high logic level signal which resets the binary coun-ter 20 and closes the gate circuit 19 to allow transmission of the second impulses representative of the number of complete periods of the wave train in the interval Tk+l to the binary counter for counting the same, and turns the transistor 21 on whereby the output voltage from the converter 14 drops to zero.
According to the above described principle, the power PS of any interval Tk is given at the output of the measuring device by the converter 13 at the beginning of the following interval, that is after the time, given by the period T=l/f of the supply voltage, required for the measurement of the power P.
As shown in Figure 2, in order to measure the average value USef of the effective voltage supplied to the load, the star/phase voltages UR, Us, UT are applied to the inputs of se-veral circuits of real effective value 22, 23, and 24, respecti-vely The outputs of these circuits 22, 23 and 24 are respectively connec-: , :
:
~3~ 36 ted to three inputs of a summator circuit 25, the output voltage of which is squared through a mul-tiplier circuit 26. The output voltage of the multiplier 26, representing the value Uef~ is connected to the first input of the comparator 8, that is to the same input as shown in Figure 1, to which the signal P
is applied.
The circuit of Figure 2 works similaxly to that des-cribed for power measuring with reference to Figure 1.
On its output, the device of Figure 2 produces the value Uef k representing the value of ths input voltage for the square-rooting circuit 27. The voltage at the output of the circuit 27 represents the average value of the effective voltage:
U f = U f ~
The method and converter according to the invention offer the advantage of measuring the electricpower and the effective voltage for trains of wave with variable number of voltage and low frequency wave periods.
Although the present invention has been described hereinabove by means of preferred embodiments thereof, it should be pointed out that any modification to these preferred embodiments within the scope of the appended claims is not deemed to change or alter the nature and scope of the invention.
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~23~ 1!36 a device for measuring an electric quantity average value related to a series of trains of a periodic wave, these wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive timeintervals, which measuring device com-prising:
means for measuring said electric quantity of the wave train produced during each of the intervalsconsidering that said wave train is ininterrupted, which measuring means comprises means for producing an electric quantity measure signal during each of the time intervals;
means for storing the electric quantity measure signal produced during each time interval;
means for producing a first impulse at the beginning of each wave train, and for producing second impulses repre-sentative of the number of complete periods of the periodic wave in each wave train;
first memory means comprising:(a) first means for counting the second impulses representative of the num~er of complete periods in the wave train produced during each of the odd ones of the successive time intervals and for producing a count value representative of the number of second impulses counted during the odd interval; (b) first means for multiplying the count value produced during the odd time intervalwith the stored electric quantity measure signal produced during the one of said intervals immediately following said odd interval in order to generate a first multiplied signal; (c) first means for storing the first multiplied signal; and ~d) first means responsive to the first impulses for supplying on an output of the measuring device the stored, first mul-tiplied signal as the electric quantity average value duringthe one of the time intervals immediately following the odd interval; and second memory means including:(a) second means for counting the second impulses representative of the number of ,. ':: ' : .~ : :
' . ,~
~23~
complete periods in the wave train produced during each of the even ones of the successive time intervals and for producin~
a count value representative of the number of second impulses counted during the even interval; (b) second means for multi-plying the count value produced during the even time intervalwith said stored electric quantity measure signal produced during the one of said time intervals immediately following said even interval in order to generate a second multiplied signal; (c) second means for storing the second multiplied signal; and (d) second means responsive to the Eirst impulses for supplying on the output of the measuring device the stored, second multi-plied signal as the electric quantity average value during the one of the successive time intervals immediately following the even interval.
The periodic wave may be an alternating voltage and the electric quantity the effective value of this alternating voltage. The periodic wave may also be formed by alternating current and voltage and the electric quantity by the electric power supplied to a load. The periodic wave may further be a three phase alternating voltage and the electric quantity the effective value of this three phase voltage. The periodic wave may still further be formed by three phase alternating current and voltage, and the electric quantity by the three phase electric power supplied to a load.
In accordance with a preferred embodiment of the inven-tion, in which the periodic wave is an alternating voltage ap-plied to a load and the electric quantity the effective voltage supplied to this load, the square of the effective voltage re-lated to the train in each time interval is measured considering a continuous supply of the load with alternating voltage, the so measured square of the effective voltage is multiplied with the number of complete periods of the periodic wave in the same wave train to produce the corresponding multiplied signal or value, and the first and second multiplied si-gnals or values are square-rooted before being delivered ~38g~l36 on the ou-tput as the electric quantity average value~
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non restrictive description of two examples of carrying out the same, given with reference to the accom-panying drawings, in which:
Figure l illustrates measurement, in accordance with the invention, of an average value of the electric power sup-plied to a load; and Figure 2 shows measurement, inaccordance with the present invention,of an average value of the efective vol-tage supplied to the load.
The average values of the electric power or of the effective voltage supplied to the load for waveforms, consis-ting of trains of wave having a variable number of complete periods of the supply voltage, are given by the following expresslons:
P k 1 ~ uidt n (1) Usef Uef ~ ~ Uef n (2) where: PS is the average value of the electric power supplied to the load;
k is the number of the complete wave periods in the train;
n is the maximal number of complete voltage wave pe-riods in a cyclic basic time interval Tk;
P is the power, for example the average or apparent power consi-dering a continuous supply oE the load by the supply networkoperating at a frequency f = 50 Hz (60 Hz);
u and i are respectively the instantaneous values of the voltage and current supplied to the load;
dt indicates derivative with respect to time;
T is the cyclic basis time interval;
'~ : 5 -..
' , :.
~3~6~
Usef is the average value of the effective voltage supplied to the load; and ~ ef is the effective voltage supplied to the load considering a continuous supply of the load with voltage from the supply network (k = n).
The electric power P is measured during the first vol-taye and current wave period applied to the load within the first Tk of successive time intervals and it is multiplied by an analog value given by a digital-to-analog converter of the real number k of voltage and load current wave periods.
A memory Ml stores the result of the multiplication represen-ting PS during the complete interval Tk,and a switching circuit transfers the value PS at the output of the measuring device at the beginning of the intervalTk+l; in the time interval Tk+l the value of Ps~ corresponding to number k + 1 of voltage and current wave periods controlled on the load, is measured again and it is stored in another memory M2, and it is trans-mitted by a switching circuit on the output of the device at the beginning of the intervalTkf2, concomitantly with the erasing of the memory Ml prepared to measure the power PS
for the interval Tk+2.
In order to measure the average value of the effective voltage supplied to a load the same circuit structure as that pre-viously described is used, but during the first alternations of each interval Tk, Tk+l the value Uef is measured, and the out-put of the device is applied to an analog square-rooting circuit according to relation 2.
As shown in Figure 1, in order to measure the apparent power P, several multiplying circuits 1,2,3 multiply the star /phase voltages UR, Us, UT with the phase currents IR, Is, IT, respectively. The signals produced at the output of the multiplying circuits l, 2 and 3 are respectively supplied to the inputs of the integrating circuits 4,5,6 having their outputs connected to three inputs of a summator 7 which produces .'.'`
`' 1~3~
an analog signal, proportional to P at its output. This si-gnal is applied to a first input of a comparator 8.
An oscjllator 9 generates impulses applied to a gate circuit 10 controlling a binary counter 11. The outputs of the counter 11 are connected to the inputs of a digital-to-analog converter 12, which converter 12 has an output con-nected to a second input of the comparator 8.
The output of the comparator 8 is applied to a second input of the gate circuit 10 and s*ops -the transmission of impulses to the counter 11, when the value of the voltage at the output of the converter 12 is equal to the amplitude of the signal delivered from the summator circuit 7, thus achieving storage of the measured information P.
The measuring cycle begins all over again at the end of eachinterval Tk by erasing the counter 11 through first impulses generated at the beginning of each wave train.
The analog signal P produced by the converter 12 re-presents the reference voltage for a pair of digital-to-analog converters 13, 14 which have a multiplying function. A flip-flop sweep switching circuit 15r controlled by second impulses generated in response to each period of the voltage applied to the load, controls the circuits of the memory M1 made up of a gate circuit 16, a binary counter 17, a commutating transistor 18 and the digital-to-analog converter 13.
The digital-to-analog converter 13 produces an output voltage representative of the value resulting from the multi-plication of P given by the converter 12, and the analog con-verted value of the wave number k supplied to the load given by the counter 17, which value expresses the value Ps~
The memory M2 similarly to the memory M1 consists of a gate circuit 19, a binary counter 20, a commutating transis-tor 21 and the digital-to-analog converter 14.
In response to the first impulse generated at the beginning of each odd interval such as Tk, the circuit 15 generates on its first input ~:3~ 36 a high logic level signal which turns the transistor 18 on and causes the output voltage of the converter 13 to drop to zero, while resetting the binary counter 17 and closing the gate circuit 16 to allow transmission of the second impulses representative of the number of complete periods of the wave train in the interval Tk toward the binary counter which counts the same. During this time, the circuit 15 generates on its second input a low logic level signal which turns the transis-tor 21 off to allow transmission of the output voltage from the converter 14 to the output of the measuring device, and which opens the gate circuit 19 to block the second impulses.
In response to the first impulse generated at the beginning of each even interval such as Tk+l, the circuit 15 generates on its first output a low logic level signal which turns the transistor 18 off whereby the output signal from the converter 13 is supplied to the output of the measuring device and the gate circuit 16 opened to stop the second impulses.
During this time, the circuit 15 also supplies on its second output a high logic level signal which resets the binary coun-ter 20 and closes the gate circuit 19 to allow transmission of the second impulses representative of the number of complete periods of the wave train in the interval Tk+l to the binary counter for counting the same, and turns the transistor 21 on whereby the output voltage from the converter 14 drops to zero.
According to the above described principle, the power PS of any interval Tk is given at the output of the measuring device by the converter 13 at the beginning of the following interval, that is after the time, given by the period T=l/f of the supply voltage, required for the measurement of the power P.
As shown in Figure 2, in order to measure the average value USef of the effective voltage supplied to the load, the star/phase voltages UR, Us, UT are applied to the inputs of se-veral circuits of real effective value 22, 23, and 24, respecti-vely The outputs of these circuits 22, 23 and 24 are respectively connec-: , :
:
~3~ 36 ted to three inputs of a summator circuit 25, the output voltage of which is squared through a mul-tiplier circuit 26. The output voltage of the multiplier 26, representing the value Uef~ is connected to the first input of the comparator 8, that is to the same input as shown in Figure 1, to which the signal P
is applied.
The circuit of Figure 2 works similaxly to that des-cribed for power measuring with reference to Figure 1.
On its output, the device of Figure 2 produces the value Uef k representing the value of ths input voltage for the square-rooting circuit 27. The voltage at the output of the circuit 27 represents the average value of the effective voltage:
U f = U f ~
The method and converter according to the invention offer the advantage of measuring the electricpower and the effective voltage for trains of wave with variable number of voltage and low frequency wave periods.
Although the present invention has been described hereinabove by means of preferred embodiments thereof, it should be pointed out that any modification to these preferred embodiments within the scope of the appended claims is not deemed to change or alter the nature and scope of the invention.
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Claims (22)
1. A method of measuring an electric quantity ave-rage value related to a series of trains of a periodic wave, said wave trains having a variable number of complete periods of the periodic wave and being each produced during a corres-ponding one of successive time intervals, said method comprising the steps of:
(a) measuring said electric quantity related to the wave train produced during a first one of said time intervals considering that said wave train is ininterrupted;
(b) measuring the number of complete periods of the periodic wave in the wave train produced during said first time interval;
(c) multiplying said electric quantity measured in step (a) with the wave period number measured in step (b) in order to produce a first multiplied value;
(d) storing said first multiplied value in a first memory means;
(e) delivering on an output the first multiplied value stored in the first memory means as said electric quantity average value during a second one of the succes-sive time intervals following the first time interval;
(f) measuring said electric quantity related to the wave train produced during the second time interval considering that said wave train is ininterrupted;
(g) measuring the number of complete periods of the periodic wave in the wave train produced during said second time interval;
(h) multiplying said electric quantity measured in step (f) with the wave period number measured in step (g) in order to produce a second multiplied value;
(i) storing said second multiplied value in a second memory means;
(j) delivering on said output the second multiplied value stored in the second memory means as said electric quan-tity average value during a third one of said successive time intervals following the second time interval; and (k) repeating steps (a) to (j) during the subsequent ones of said successive time intervals starting from said third time interval
(a) measuring said electric quantity related to the wave train produced during a first one of said time intervals considering that said wave train is ininterrupted;
(b) measuring the number of complete periods of the periodic wave in the wave train produced during said first time interval;
(c) multiplying said electric quantity measured in step (a) with the wave period number measured in step (b) in order to produce a first multiplied value;
(d) storing said first multiplied value in a first memory means;
(e) delivering on an output the first multiplied value stored in the first memory means as said electric quantity average value during a second one of the succes-sive time intervals following the first time interval;
(f) measuring said electric quantity related to the wave train produced during the second time interval considering that said wave train is ininterrupted;
(g) measuring the number of complete periods of the periodic wave in the wave train produced during said second time interval;
(h) multiplying said electric quantity measured in step (f) with the wave period number measured in step (g) in order to produce a second multiplied value;
(i) storing said second multiplied value in a second memory means;
(j) delivering on said output the second multiplied value stored in the second memory means as said electric quan-tity average value during a third one of said successive time intervals following the second time interval; and (k) repeating steps (a) to (j) during the subsequent ones of said successive time intervals starting from said third time interval
2. The method of claim 1, comprising the steps of erasing the second memory means at the beginning of the second time interval, and erasing the first memory means at the begin-ning of the third time interval.
3. A method according to claim 1 or 2, wherein said periodic wave is an alternating voltage applied to a load, wherein said electric quantity is the effective alternating voltage applied to the load, whe-rein said measuring steps (a) and (f) each comprise measuring the square of the effective voltage applied to the load considering a continuous supply of the load with alter-nating voltage, wherein said multiplying step (c) comprises multiplying the square of the effective voltage measured in step (a) with the wave period number measured in step (b) in order to produce the first multiplied value, and wherein said multiplying step (h) comprises multiplying the square of the effective voltage measured in step (f) with the wave period number measured in step (g) in order to produce the second multiplied value, and wherein said delivering steps (e) and (j) comprise the step of square rooting the first and second multiplied values, respectively, in order to deliver said electric quantity average value.
4. A method of measuring a voltage average value related to a series of trains of a periodic, three-phase al-ternating voltage, said trains having a variable number of complete periods of the three-phase alternating voltage and being each produced during a corresponding one of successive time intervals, said method comprising the steps of:
(a) measuring a squared voltage value related to the alter-nating voltage train produced during a first one of said time intervals considering that said alternating voltage train is ininterrupted;
(b) measuring the number of complete periods of the three-phase alternating voltage in the train produced during said first time interval;
(c) multiplying said squared voltage value measured in step (a) with the period number measured in step (b) in order to produce a first multiplied value;
(d) storing said first multiplied value in a first memory means;
(e) during a second one of the successive time intervals following the first time interval, square rooting the first multiplied value stored in the first memory means and deli-vering on an output said square-rooted value as said voltage average value;
(f) measuring a squared voltage value related to the alterna-ting voltage train produced during the second time interval considering that said alternating voltage train in ininter-rupted;
(g) measuring the number of complete periods of the three-phase alternating voltage in the train produced during said second time interval;
(h) multiplying said squared voltage value measured in step (f) with the period number measured in step (g) in order to produce a second multiplied value;
(i) storing said second multiplied value in a second memory means;
(j) during a third one of said successive time intervals follo-wing the second time interval, square-rooting the second multiplied value stored in the second memory means and delivering on said output said square-rooted second multiplied value as said voltage average value; and (k) repeating steps (a) to (j) during the subsequent ones of said successive time intervals starting from said third time interval.
(a) measuring a squared voltage value related to the alter-nating voltage train produced during a first one of said time intervals considering that said alternating voltage train is ininterrupted;
(b) measuring the number of complete periods of the three-phase alternating voltage in the train produced during said first time interval;
(c) multiplying said squared voltage value measured in step (a) with the period number measured in step (b) in order to produce a first multiplied value;
(d) storing said first multiplied value in a first memory means;
(e) during a second one of the successive time intervals following the first time interval, square rooting the first multiplied value stored in the first memory means and deli-vering on an output said square-rooted value as said voltage average value;
(f) measuring a squared voltage value related to the alterna-ting voltage train produced during the second time interval considering that said alternating voltage train in ininter-rupted;
(g) measuring the number of complete periods of the three-phase alternating voltage in the train produced during said second time interval;
(h) multiplying said squared voltage value measured in step (f) with the period number measured in step (g) in order to produce a second multiplied value;
(i) storing said second multiplied value in a second memory means;
(j) during a third one of said successive time intervals follo-wing the second time interval, square-rooting the second multiplied value stored in the second memory means and delivering on said output said square-rooted second multiplied value as said voltage average value; and (k) repeating steps (a) to (j) during the subsequent ones of said successive time intervals starting from said third time interval.
5. A measuring method according to claim 4, com-prising the steps of erasing the second memory means at the beginning of the second time interval, and erasing the first memory means at the beginning of the third time interval.
6. A measuring method according to claim 4, wherein said three-phase voltage comprises three single phase alter-nating voltages, and wherein each of the squared voltage value measuring steps (a) and (f) comprises separately measuring said single phase voltages, summing the so measured single phase voltages to produce a sum signal, and squaring said sum signal to produce the squared voltage value.
7 A method of measuring an average value of the electric power supplied to an electric load fed with a series of trains of periodic, alternating voltage and current, said trains com-prising a variable number of complete periods of the alter-nating voltage and being each produced during a corresponding one of successive time intervals, said method comprising the steps of:
(a) measuring for a first one of said time intervals the electric power supplied to the load considering that the train of alternating voltage and current of said first interval is ininterrupted;
(b) measuring the number of complete periods of the alternating voltage in the voltage and current train produced during said first time interval;
(c) multiplying the power measure of step (a) with the period number measured in step (b) in order to produce a first multiplied value;
(d) storing said first multiplied value in a first memory means;
(e) delivering on an output the first multiplied value stored in the first memory means as said elec-tric power average value during a second one of the successive time intervals following said first interval;
(f) measuring for the second time interval the electric power supplied to the load considering that the train of alternating voltage and current of the second interval is inin-terrupted;
(g) measuring the number of complete periods of the alternating voltage in the voltage and current train produced during said second time interval;
(h) multiplying the power measure of step (f) with the period number measured in step (g) in order to produce a second multiplied value;
(i) storing said second multiplied value in a second memory means;
(j) delivering on said output the second multiplied value stored in the second memory means as said elec-tric power average value during a third one of said successive time intervals following the second time interval ;
and (k) repeating steps (a) to (j) during the subsequent ones of said successive time intervals starting from said third time interval.
(a) measuring for a first one of said time intervals the electric power supplied to the load considering that the train of alternating voltage and current of said first interval is ininterrupted;
(b) measuring the number of complete periods of the alternating voltage in the voltage and current train produced during said first time interval;
(c) multiplying the power measure of step (a) with the period number measured in step (b) in order to produce a first multiplied value;
(d) storing said first multiplied value in a first memory means;
(e) delivering on an output the first multiplied value stored in the first memory means as said elec-tric power average value during a second one of the successive time intervals following said first interval;
(f) measuring for the second time interval the electric power supplied to the load considering that the train of alternating voltage and current of the second interval is inin-terrupted;
(g) measuring the number of complete periods of the alternating voltage in the voltage and current train produced during said second time interval;
(h) multiplying the power measure of step (f) with the period number measured in step (g) in order to produce a second multiplied value;
(i) storing said second multiplied value in a second memory means;
(j) delivering on said output the second multiplied value stored in the second memory means as said elec-tric power average value during a third one of said successive time intervals following the second time interval ;
and (k) repeating steps (a) to (j) during the subsequent ones of said successive time intervals starting from said third time interval.
8. A measuring method according to claim 7, in which each power measuring steps (a) and (f) comprises multiplying the voltage and current of the train to produce an output signal, and integrating said output signal produced during the voltage and current multiplying step.
9. A measuring method according to claim 7, in which said alternating voltage and current are three phase alternating voltage and current comprising three sets of sin-gle phase alternating voltage and current, and wherein each of said power measuring steps (a) and (f) comprises separa-tely multiplying the single phase voltage and current of each set and integrating the so multiplied single phase voltage and current to produce an integration signal, and summing the three integration signals in order to obtain the power measure.
10. A device for measuring an electric quantity average value related to a series of trains of a periodic wave, said wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive time intervals, said measuring device comprising:
means for measuring said electric quantity of the wave train produced during each of said intervals considering that said wave train is ininterrupted, said measuring means comprising means for producing an electric quantity measure signal during each of said time intervals;
means for storing said electric quantity measure si-gnal produced during each time interval;
means for producing a first impulse at the beginning of each wave train, and for producing second impulses representative of the number of complete periods of the periodic wave in each wave train;
first memory means comprising:(a) first means for counting the second impulses representative of the number of complete periods in the wave train produced during each of the odd ones of the successive time intervals and for producing a count value representative of the number of second impulses counted during the odd interval; (b) first means for multiplying the count value produced during the odd time interval with said stored electric quantity measure signal produced during the one of said intervals immediately following said odd interval in order to generate a first multiplied signal; (c) first means for storing said first multiplied signal; and (d) first means responsive to the first impulses for supplying on an output of the measuring device the stored, first multiplied signal as said electric quantity average value during the one of said time intervals immediately following said odd interval; and second memory means including:(a) second means for counting the second impulses representative of the number of complete periods in the wave train produced during each of the even ones of the successive time intervals and for producing a count value representative of the number of second impulses counted during the even interval; (b) second means for multi-plying the count value produced during the even time interval with said stored electric quantity measure signal produced during the one of said time intervals immediately following said even interval in order to generate a second multiplied signal; (c) second means for storing said second multiplied signal; and (d) second means responsive to the first impulses for supplying on said output of the measuring device the stored, second multiplied signal as said electric quantity average va-lue during the one of said successive time intervals immediate-ly following said even interval.
means for measuring said electric quantity of the wave train produced during each of said intervals considering that said wave train is ininterrupted, said measuring means comprising means for producing an electric quantity measure signal during each of said time intervals;
means for storing said electric quantity measure si-gnal produced during each time interval;
means for producing a first impulse at the beginning of each wave train, and for producing second impulses representative of the number of complete periods of the periodic wave in each wave train;
first memory means comprising:(a) first means for counting the second impulses representative of the number of complete periods in the wave train produced during each of the odd ones of the successive time intervals and for producing a count value representative of the number of second impulses counted during the odd interval; (b) first means for multiplying the count value produced during the odd time interval with said stored electric quantity measure signal produced during the one of said intervals immediately following said odd interval in order to generate a first multiplied signal; (c) first means for storing said first multiplied signal; and (d) first means responsive to the first impulses for supplying on an output of the measuring device the stored, first multiplied signal as said electric quantity average value during the one of said time intervals immediately following said odd interval; and second memory means including:(a) second means for counting the second impulses representative of the number of complete periods in the wave train produced during each of the even ones of the successive time intervals and for producing a count value representative of the number of second impulses counted during the even interval; (b) second means for multi-plying the count value produced during the even time interval with said stored electric quantity measure signal produced during the one of said time intervals immediately following said even interval in order to generate a second multiplied signal; (c) second means for storing said second multiplied signal; and (d) second means responsive to the first impulses for supplying on said output of the measuring device the stored, second multiplied signal as said electric quantity average va-lue during the one of said successive time intervals immediate-ly following said even interval.
11. A device for measuring an electric quantity average value related to a series of trains of a periodic wave, said wave trains having a variable number of complete periods of the periodic wave and being each produced during a corresponding one of successive time intervals, said measuring device comprising:
means for measuring said electric quantity of the wave train produced during each of said time intervals consi-dering that said wave train is ininterrupted, said measuring means comprising means for producing an electric quantity analog measure signal during each of said time intervals;
means for storing said analog measure signal produced during each time interval,comprising: a comparator having a first input receiving said analog measure signal; an oscillator for supplying first impulses; a first binary counter for count-ing said first impulses and for producing a corresponding out-put binary count; a gate circuit through which the first im-pulses are transmitted to the first binary counter; a first digital-to-analog converter for converting the output binary count from the first binary counter into an analog count value supplied on an output of the first converter; said comparator having a second input receiving the analog count value from the first digital-to-analog converter and an output for delivering a control signal when said analog count value from the first converter reaches an amplitude equal to the amplitude of said analog measure signal from the electric quantity measuring means, said gate circuit comprising a control input receiving said control signal from the comparator to stop transmission of the first impulses from the oscillator to the first binary counter whereby said analog measure signal is stored into analog form at the output of the first digital-to-analog converter;
means for producing a second impulse at the beginning of each wave train, and for producing third impulses representative of the number of complete periods of the periodic wave in each wave train;
first memory means comprising: a second gate circuit;
a second binary counter for counting the third impulses repre-sentative of the number of complete periods in the wave train produced during each of the odd ones of the time intervals, said second binary counter having an input receiving said third impulses through the second gate circuit and an output for delivering a binary count value representative of the number of third impulses counted during the odd interval; a second digital-to-analog converter comprising a first input connected to the output of the second binary counter, a second input connected to the output of the first digital-to-analog conver-ter, first means for multiplying the binary count value of the odd interval on the output of the second binary counter with the analog count value of the one of said successive intervals following said odd interval on the output the first digital-to-analog converter to produce an analog signal representative of the measure of said electric quantity average value, and first means for storing said average value measure represen-tative signal; and first means responsive to the second im-pulses for supplying on an output of the measuring device, during the one of said time intervals immediately following said odd period, said average value measure representative signal stored in said first storing means; and second memory means comprising: a third gate cir-cuit; a third binary counter for counting the third impulses representative of the number of complete periods in the wave train produced during each of the even ones of the time inter-vals, said third binary counter having an input receiving the third impulses through the third gate circuit and an output for delivering a binary count value representative of the number of third impulses counted during the even interval; a third digital-to-analog converter comprising a first input connected to the output of the third binary counter, a second input con-nected to the output of the first digital-to-analog converter, second means for multiplying the binary count value of the even interval on the output of the third binary counter with the analog count value of the one of said successive intervals immediately following said even period on the output of the first digital-to-analog converter to produce an analog signal repre-sentative of the measure of the electric quantity average value, and second means for storing said average value measure representative signal; and second means res-ponsive to the second impulses for supplying on said output of the measuring device, during the one of said time periods immediately following said even period, said average value measure representative signal stored in said second storing means.
means for measuring said electric quantity of the wave train produced during each of said time intervals consi-dering that said wave train is ininterrupted, said measuring means comprising means for producing an electric quantity analog measure signal during each of said time intervals;
means for storing said analog measure signal produced during each time interval,comprising: a comparator having a first input receiving said analog measure signal; an oscillator for supplying first impulses; a first binary counter for count-ing said first impulses and for producing a corresponding out-put binary count; a gate circuit through which the first im-pulses are transmitted to the first binary counter; a first digital-to-analog converter for converting the output binary count from the first binary counter into an analog count value supplied on an output of the first converter; said comparator having a second input receiving the analog count value from the first digital-to-analog converter and an output for delivering a control signal when said analog count value from the first converter reaches an amplitude equal to the amplitude of said analog measure signal from the electric quantity measuring means, said gate circuit comprising a control input receiving said control signal from the comparator to stop transmission of the first impulses from the oscillator to the first binary counter whereby said analog measure signal is stored into analog form at the output of the first digital-to-analog converter;
means for producing a second impulse at the beginning of each wave train, and for producing third impulses representative of the number of complete periods of the periodic wave in each wave train;
first memory means comprising: a second gate circuit;
a second binary counter for counting the third impulses repre-sentative of the number of complete periods in the wave train produced during each of the odd ones of the time intervals, said second binary counter having an input receiving said third impulses through the second gate circuit and an output for delivering a binary count value representative of the number of third impulses counted during the odd interval; a second digital-to-analog converter comprising a first input connected to the output of the second binary counter, a second input connected to the output of the first digital-to-analog conver-ter, first means for multiplying the binary count value of the odd interval on the output of the second binary counter with the analog count value of the one of said successive intervals following said odd interval on the output the first digital-to-analog converter to produce an analog signal representative of the measure of said electric quantity average value, and first means for storing said average value measure represen-tative signal; and first means responsive to the second im-pulses for supplying on an output of the measuring device, during the one of said time intervals immediately following said odd period, said average value measure representative signal stored in said first storing means; and second memory means comprising: a third gate cir-cuit; a third binary counter for counting the third impulses representative of the number of complete periods in the wave train produced during each of the even ones of the time inter-vals, said third binary counter having an input receiving the third impulses through the third gate circuit and an output for delivering a binary count value representative of the number of third impulses counted during the even interval; a third digital-to-analog converter comprising a first input connected to the output of the third binary counter, a second input con-nected to the output of the first digital-to-analog converter, second means for multiplying the binary count value of the even interval on the output of the third binary counter with the analog count value of the one of said successive intervals immediately following said even period on the output of the first digital-to-analog converter to produce an analog signal repre-sentative of the measure of the electric quantity average value, and second means for storing said average value measure representative signal; and second means res-ponsive to the second impulses for supplying on said output of the measuring device, during the one of said time periods immediately following said even period, said average value measure representative signal stored in said second storing means.
12. A device according to claim 10 or 11, wherein said periodic wave is an alternating voltage, and wherein said electric quantity is the effective value of said alter-nating voltage.
13. A device according to claim 10 or 11, wherein said periodic wave is formed by alternating current and voltage, and wherein said electric quantity is the electric power supplied to a load.
14. A device according to claim 10 or 11, wherein said periodic wave is a three phase alternating voltage and wherein said electric quantity is the effective value of said three phase alternating voltage.
15. A device according to claim 10 or 11, wherein said periodic wave is formed by three phase alternating cur-rent and voltage, and wherein said electric quantity is the three phase electric power supplied to a load.
16. A device according to claim 11, further comprising means for resetting said first binary counter in response to each of said second pulse.
17. A device according to claim 10 or 11, wherein said periodic wave is an alternating voltage, and wherein said electric quantity measured by said electric quantity measuring means is the square of the effective value of said alternating voltage, said measuring device further comprising a circuit for square-rooting the signals stored in said first storing means of the first memory means and in said second storing means of the second memory means before supplying the same on said output of the measuring device.
18. A device according to claim 10, comprising means responsive to the first impulses for resetting the first memory means at the beginning of each odd one of said time intervals and means for resetting the second memory means at the begin-ning of each even one of said successive time intervals.
19. A device according to claim 18, wherein said first multiplied signal supplying means of the first memory means, said second multiplied signal supplying means of the second memory means, said means for resetting the first memory means and said means for resetting the second memory means comprise flip-flop means having an input on which the first impulses are supplied, a first output connected to the first memory means, and a second output connected to the second memory means.
20. The measuring method of claim 1, in which the electric quantity measured in step (a) is the electric quan-tity of the wave train produced during the second interval, and the electric quantity measured in step (f) is the elec-tric quantity of the wave train produced during the third interval.
21. The measuring method of claim 4, wherein the squared voltage value measured in step (a) is a squared voltage value of the voltage train produced during the second interval, and the squared voltage value measured in step (f) is a squared voltage value of the voltage train produced during the third interval.
22. The measuring method of claim 7, wherein the electric power measured in step (a) for the first time inter-val is the power supplied to the load during the second in-terval, and the electric power measured in step (f) for the second time interval is the power supplied to the load during the third interval.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| RO114364A RO86362B1 (en) | 1984-04-24 | 1984-04-24 | Method for determining the efficent value and efficient value electronic converter for carrying out the same |
| RO114364 | 1984-04-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1238686A true CA1238686A (en) | 1988-06-28 |
Family
ID=20114805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000479851A Expired CA1238686A (en) | 1984-04-24 | 1985-04-23 | Method and device for measuring an electric quantity average value related to a series of periodic wave trains |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1238686A (en) |
| RO (1) | RO86362B1 (en) |
| SU (1) | SU1501930A3 (en) |
-
1984
- 1984-04-24 RO RO114364A patent/RO86362B1/en unknown
-
1985
- 1985-04-23 CA CA000479851A patent/CA1238686A/en not_active Expired
- 1985-04-24 SU SU853890705A patent/SU1501930A3/en active
Also Published As
| Publication number | Publication date |
|---|---|
| RO86362B1 (en) | 2002-06-28 |
| SU1501930A3 (en) | 1989-08-15 |
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