JPH07113649B2 - Reactive energy meter - Google Patents

Description

Description: [Object of the Invention] (Industrial field of application) [0001] The present invention relates to a reactive power meter, and more particularly to a reactive power capable of accurately measuring reactive power without being affected by frequency fluctuations. Regarding the meter.

(Prior Art) For example, a voltage V is supplied to a load via a power supply line, and a current I
It is well known that the reactive power Q when is consumed is expressed by the following equation.

Q = VI sin θ (1) where θ is the phase difference between the load voltage V and the consumption current I. In this case, the active power P consumed by the load is expressed by the following equation.

P = VI cos θ Here, sin θ and cos θ have the following relationship.

sin θ = cos (θ = π / 2) Therefore, the reactive power Q can be obtained by delaying the phase of either the load voltage V or the consumption current I by π / 2 and multiplying both.

FIG. 7 is a block diagram of a conventional electronic reactive watt-hour meter that obtains the amount of reactive power by the method described above. This reactive energy meter
The load voltage V applied to the power supply line is detected by the voltage detection unit 101, and as shown in FIG.
Is converted into a voltage signal v proportional to
The consumption current I flowing through the power supply line is detected by 102, and the eighth
As shown in (c) of the figure, it is converted into a current i proportional to the consumption current I. The voltage signal v from the current detection unit 101 is delayed in phase by π / 2 by the delay unit 103, supplied to the power multiplication unit 104 as the voltage signal va shown in FIG. The current signal i from the power signal is also supplied to the power multiplication unit 104, where the voltage signal va and the current signal i
Are multiplied by and the voltage signal vq proportional to the reactive power Q is obtained from the power multiplication unit 104. This voltage signal vq is converted into a frequency signal fout by the voltage-frequency conversion unit 105, and the reactive power amount is obtained by accumulating the frequency signal fout.

(Problems to be Solved by the Invention) In the above-mentioned conventional reactive energy meter, in order to accurately measure the reactive energy, it is necessary to accurately delay the phase of the voltage signal v by π / 2 in the delay unit 103. Required, but delay
Since 103 is composed of a coil, a capacitor, a resistor, etc., when the frequency of the power supply connected to the power supply line fluctuates, the impedance of the coil and the capacitor changes, which causes the voltage signal va output from the delay unit 103. Has a problem that it is difficult to accurately measure the unscented electric energy.

More specifically, for example, when the delay unit 103 is composed of an RC filter that operates as an integrating circuit, the voltage signal va is given by the following equation.

Therefore, the maximum amplitude of the voltage signal va Varies with (1 / ω), which makes it difficult to measure the reactive power accurately.

Furthermore, the frequency of commercial power is 50Hz and 60Hz depending on the region.
There are two types of reactive watt-hour meters and it is necessary to prepare two types of reactive watt-hour meters according to the type of this frequency, so not only the design of the reactive watt-hour meter becomes complicated, but also the number of manufacturing processes increases. There is also the problem that inventory management of two types of reactive energy meters is also required.

The present invention has been made in view of the above, and an object of the present invention is to provide a reactive energy meter that can accurately measure reactive energy even if the frequency changes.

[Structure of the Invention] (Means for Solving Problems) In order to solve the above problems, a reactive power meter of the present invention is
The first voltage proportional to the voltage detected by the voltage supplied to the load is detected.
Voltage detecting means for generating a voltage signal, a current detecting means for detecting a current supplied to a load, and generating a second voltage signal proportional to the current, and one of the first and second voltage signals. And a power multiplying means for outputting a voltage signal proportional to the reactive power based on the delayed output signal from the delay means and the other voltage signal of the first and second voltage signals. A reference voltage generating means for generating a reference voltage inversely proportional to the frequency of the first or second voltage signal, and a frequency proportional to the reactive power based on the voltage signal from the power multiplying means and the reference voltage. The gist is to have a voltage-frequency conversion means for generating a signal.

(Operation) In the reactive energy meter of the present invention, one of the first and second voltage signals proportional to the voltage and current supplied to the load is delayed, and the delayed voltage signal and the other are not delayed. A voltage signal proportional to the reactive power based on the voltage signal and a reference voltage inversely proportional to the frequency of the first or second voltage signal, and the reference voltage and the voltage signal proportional to the reactive power. A signal having a frequency proportional to the reactive power is generated based on.

(Examples) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a reactive energy meter according to an embodiment of the present invention. The reactive energy meter in the figure detects the voltage V supplied to the load via, for example, a power supply line, and detects the load voltage V
The consumption current I flowing to the load via the voltage detection unit 1 that outputs the first voltage signal ev proportional to
It has a current detector 2 that outputs a second voltage signal ei proportional to the consumption current I. The voltage detection unit 1 and the current detection unit 2 are each configured by, for example, a transformer and a current transformer.

The first voltage signal ev from the voltage detection unit 1 is supplied to the delay unit 3, its phase is delayed by π / 2, and is supplied to one input of the power multiplication unit 4 as the first delay voltage signal eva. And is supplied to the reference voltage generator 5. Further, the second voltage signal ei from the current detection unit 2 is directly supplied to the other input of the power multiplication unit 4. The voltage detection unit 1, the current detection unit 2 and the delay unit 3 constitute a load detection unit.

The power multiplication unit 4 multiplies the first delay voltage signal eva and the second voltage signal ei and outputs the power multiplication voltage signal eq. The power-multiplied voltage signal eq is supplied to the voltage-frequency conversion unit 6, and the voltage-frequency conversion unit 6 is also supplied with the reference voltage signal er from the reference voltage generation unit 5. The reference voltage generator 5 is supplied with the first voltage signal ev from the voltage detector 1 as described above. The reference voltage generator 5 is supplied with the first voltage signal ev from the voltage detector 1 as described above, detects the frequency of the first voltage signal ev, and outputs the reference voltage signal er corresponding to this frequency. Occur. The voltage-frequency conversion unit 6 converts the power-multiplied voltage signal eq from the power multiplication unit 4 into a frequency signal fq proportional to the reactive power while correcting the power-multiplied voltage signal eq based on the reference voltage signal er from the reference voltage generation unit 5 to change the frequency. It is output as one that has no effect.

Next, the reference voltage generator 5 will be described in detail with reference to FIG. The reference voltage generating section 5 shown in FIG. 2 has a waveform shaping section 52 that shapes the waveform of the first voltage signal ev from the voltage detecting section 1. The first voltage signal ev is waveform-shaped by the waveform shaping unit 52 into a square waveform, and is D as the frequency signal fv.
Type flip-flops 53 and 54 are supplied to the clock terminal ck. Further, the reference voltage generator 5 has a reference time generator 51 for generating a reference frequency signal fr having a reference frequency equal to or lower than the frequency of the feeder line. The reference frequency signal fr from the reference time generator 51 is a D-type flip-flop. It is supplied to the set terminal S of the loop 53. When the reference frequency signal fr is supplied from the reference time generator 51 to the set terminal S, the D-type flip-flop 53 outputs a 1-level output signal Qa. Also D
The 0 level signal is supplied to the data input D of the D-type flip-flop 53.
When the frequency signal fv is supplied to the clock terminal ck of the D-type flip-flop 53,
The level signal is latched and the 0 level signal output signal Qa is output.

The output terminal Q of the D-type flip-flop 53 is further connected to the data input D of another D-type flip-flop 54, whereby the D-type flip-flop at the time when the frequency signal fv is supplied to the clock terminal ck of the D-type flip-flop 54. The output signal Qa from the amplifier 53 is latched by the D-type flip-flop 54 and output as the time pulse signal Qb. The output terminal Q of the D flip-flop 54 is connected to the changeover switch 56, and the operation of the changeover switch 56 is controlled by the time pulse Qb.

FIG. 3 shows the reference frequency signal fr in the reference voltage generator 5,
It is a wave form diagram which shows the time relationship of the frequency signal fv, the output signal Qa, and the output signal Qb. 3 (a) to 3 (c) show waveforms when the frequency of the frequency signal fv is varied with respect to the reference frequency signal fr having the same frequency, and FIG. 3 (a) shows the frequency. The frequency of the signal fv is
FIG. 3 is a waveform diagram when the frequency of fr is twice, (b) is three times, and (c) is 1.5 times.

As shown in each of FIGS. 3 (a), (b), and (c), the D-type flip-flop 53 is set every time the reference frequency signal fr is supplied from the reference time generator 51, and its output signal is output. Qa becomes 1 level, but the frequency signal fv from the waveform shaping unit 52 is the clock terminal c of the D-type flip-flops 53 and 54.
When supplied to k, the 1-level output signal Qa is latched by the D-type flip-flop 54, and the D-type flip-flop 54 outputs the 1-level output signal Qb, that is, the time pulse signal Qb, and the D-type flip-flop 54. The output signal Qa becomes 0 level because the output signal Qa is reset. The output signal Qa of the D flip-flop 53 is the next reference frequency signal fr
D level flip-flop 54
When the frequency signal fv rises again until the next reference frequency signal fr of the time pulse signal Qb, the output signal Qa of 0 level is latched by the D-type flip-flop 54 at this rise, and the time pulse signal Qb becomes 0. Become a level. As a result, D
-Type flip-flop 54 outputs the time pulse signal Qb
Indicates the time Tv of one cycle of the frequency signal fv with respect to the time Tr of one cycle of the reference frequency signal fr as shown in the figure.
As shown in FIG. 3 (c), the second signal of the frequency signal fv
When the next reference frequency signal fr is generated before the rising edge of, the output signal Qa of the D-type flip-flop 53 becomes 1 level, and the rising edge of the next frequency signal fv becomes a new first rising edge. Type flip-flop 53 output signal Qa
Becomes 0 level, but the time pulse signal Qb of the D-type flip-flop 54 is maintained at 1 level until the second rise of the frequency signal fv.

As described above, the time pulse signal Qb output from the D-type flip-flop 54 controls the changeover switch 56, and when the time pulse signal Qb is 1 level, the changeover switch 56 is connected to the contact 56a side and the time pulse signal Qb. Is 0 level, the changeover switch 56 is connected to the contact 56b. Contact 5 of changeover switch 56
A reference power source 55 having a reference voltage Vr is connected between 6a and the contact 56b so as to connect its positive electrode side to the contact 56a.
6b is connected to 0 level ground. Further, the changeover contact of the changeover switch 56 is connected to the integrating section 57 including a resistor 57a and a capacitor 57b.

Then, in the thus constructed structure, the changeover switch 56 is provided with the time pulse signal from the D-type flip-flop 54.
By the switching control by Qb, the reference voltage Vr of the reference power supply 55 is switched between the reference voltage Vr and the 0 level according to the switching operation, and the reference voltage Vr and the 0 level signal are alternately switched. The integrated signal is supplied to the integration unit 57.
Output as a reference voltage signal er.

Next, details of the voltage-frequency conversion unit 6 will be described with reference to FIG. The voltage-frequency conversion unit 6 is the power multiplication unit 4
The power multiplied voltage signal eq from the direct switch 62 is directly supplied to one contact 62a of the changeover switch 62, and the power multiplied voltage signal eq is inverted via the inverting amplifier 61 and supplied to the other contact 62b of the changeover switch 62. The power multiplication voltage signal eq and its inverted power multiplication voltage signal -eq are alternately taken out by the on / off switching operation of the changeover switch 62, and this signal is output as shown in (a) of FIG. 5 (a) or (b). The voltage signal em is supplied to the inverting input terminal of the operational amplifier 64 via the resistor 63. A capacitor 65 is connected between the output terminal and the inverting input terminal of the operational amplifier 64 to form an integrating circuit, which integrates the voltage signal em from the changeover switch 62 to generate a fifth signal.
The integrated voltage signal ec as shown in (b) of FIG. 10A or 10B is supplied to the non-inverting input which is one input of the comparator 66. The non-inverting input terminal of the operational amplifier 64 is connected to ground.

Further, the voltage-frequency conversion unit 6 directly receives the reference voltage signal er from the reference voltage generation unit 5 from one contact 68a of the changeover switch 68.
And the reference voltage signal er is supplied to the inverting amplifier 67.
Is inverted and supplied to the other contact 68b of the changeover switch 68, the reference voltage signal er and its inverted reference voltage signal -er are alternately taken out by the on / off operation of the changeover switch 68, and this signal is output to the fifth point. (C) of figure (a) or (b)
As shown in, the reference voltage signal erx for comparison is supplied to the inverting input which is the other input of the comparator 66.

The comparator 66 outputs the integrated voltage signal ec and the reference voltage signal for comparison.
erx is compared, and a positive frequency signal fq which is a positive pulse is output when the integrated voltage signal ec is larger than the reference voltage signal erx for comparison as shown in (d) of FIG. 5 (a) or (b). When the integrated voltage signal ec is smaller than the comparison reference voltage signal erx, the negative frequency signal fq, which is a negative pulse, is output.

The frequency signal fq output from the comparator 66 is calculated as a reactive power amount by being cumulatively calculated by a circuit (not shown), and this frequency signal fq is simultaneously supplied to the changeover switches 62 and 68, whereby the changeover switch 62.
And 68 to control the on / off switching operation. In FIGS. 5 (a) and 5 (b), times ta and tb are switching times of the change-over switches 62 and 68 which are thus change-controlled by the frequency signal fq, and time ta is one of the change-over switches 62 and 68. The time when the switches 62 and 68 are connected to the contacts 62a and 68a.
Time connected to b and 68b.

The operation of the reactive energy meter configured as above will be described below.

The voltage detection unit 1 detects the load voltage V supplied to the power supply line, converts the load voltage V into a first voltage signal ev proportional to the load voltage value, and supplies the first voltage signal ev to the delay unit 3. The delay unit 3 delays the phase of the first voltage signal ev by π / 2 and supplies it to the power multiplication unit 4 as the first delayed voltage signal eva. On the other hand, the current detection unit 2 detects the consumption current I flowing through the power supply line, converts the consumption current I into a second voltage signal ei proportional to the consumption current value, and supplies the second voltage signal ei to the power multiplication unit 4. Here, when the phase difference between the load voltage V and the consumption current I is θ, the first voltage signal ev and the second voltage signal ei are respectively expressed by the following equations.

In addition, the first delay voltage signal ev delayed by the delay unit 3
a is expressed by the following equation, where K1 is the constant of the delay unit 3.

The power multiplication unit 4 uses the first delay voltage signal ev from the delay unit 3.
a and the second voltage signal ei from the current detection unit 2 are multiplied,
The power multiplication voltage signal eq shown in the following equation is output.

eq = K2 · eva · ei (6) where K2 is a constant of the power multiplication unit 4.

When the above equations (4) and (5) are substituted into this equation (6), the following equation is obtained.

In this equation, (K1 · K2 / ω) VI · cos (2ωt−π / 2) on the right side
Since −θ) becomes zero when the average value is obtained, the power multiplication voltage signal eq is expressed by the following equation by passing it through the low-pass filter circuit at the output stage of the power multiplication unit 4.

The power multiplied voltage signal eq includes a frequency component of ω = 2πf, and the power multiplied voltage signal eq is supplied to the voltage-frequency conversion unit 6.

On the other hand, in the reference voltage generation unit 5, the first voltage signal ev from the voltage detection unit 1 is shaped into a square wave by the waveform shaping unit 52,
The frequency signal fv is supplied to the clock terminals ck of the D-type flip-flops 53 and 54. Further, the reference frequency signal fr from the reference time generation unit 51, which is equal to or lower than the frequency of the power supply line, is supplied to the set terminal S of the D-type flip-flop 53, and the D-type flip-flop 53 outputs the output signal Qa as shown in FIG. Is output. This output signal Qa is supplied to the data input D of the D-type flip-flop 54, and the D-type flip-flop 54 outputs the time pulse signal Qb as shown in FIG. This time pulse signal Qb is the time Tr of one cycle of the reference frequency signal fr.
1 shows the time Tv of one cycle of the frequency signal fv.

The time pulse signal Qb drives the changeover switch 56, and when the time pulse Qb is 1 level, the changeover contact of the changeover switch 56 is connected to the contact 56a to output the reference voltage Vr of the reference power source 55,
When the time pulse signal Qb is 0 level, it is connected to the contact 56b and 0
Output v. The output voltage from the selector switch 56 is
It is integrated in 7 and supplied to the voltage-frequency conversion unit 6 as the reference voltage signal er. This reference voltage signal er is expressed by the following equation.

er = (Tv / Tr) * Vr = (fr / fv) * Vr (9) Note that fr and fv are the frequencies of the reference frequency signal fr and the frequency signal fv, respectively.

The voltage-frequency conversion unit 6 corrects the power multiplication voltage signal eq from the power multiplication unit 4 based on the reference voltage signal er from the reference voltage generation unit 5, and is proportional to the reactive power that is not affected by the fluctuation of the frequency of the power supply line. Output the frequency signal fq.

That is, in the voltage-frequency conversion unit 6, the power multiplication voltage signal eq from the power multiplication unit 4 is alternately changed by the switching operation of the changeover switch 62 as shown in (a) of FIGS. Is converted into a voltage signal em which is a positive and negative voltage pulse, is integrated by an integrating circuit including an operational amplifier 64, and is output as a comparator 66 as an integrated voltage signal ec as shown in (b) of FIGS. 5 (a) and 5 (b). Is supplied to the non-inverting input of.

On the other hand, the reference voltage signal er from the reference voltage generator 5 is alternately positive and negative reference voltage signal er for comparison as shown in (c) of FIGS.
It is supplied to the inverting input of the comparator 66 as x.

The comparator 66 compares the integrated voltage signal ec with the comparison reference voltage signal erx, outputs a positive frequency signal fq when the integrated voltage signal ec is larger than the comparison reference voltage signal erx, and the integrated voltage signal ec compares When it is smaller than the reference voltage signal erx for use, a negative frequency signal fq is output. The frequency signal fq output from the comparator 66 controls the switching operation of the changeover switches 62 and 68. comparator
If the time ta when the frequency signal fq output from 66 is at a positive level and the time when it is at a negative level are tb,
The inversion period To of the frequency signal fq is given by the following equation.

To = ta + tb (10) Therefore, the frequency fq of the frequency signal fq is as follows.

fq = 1 / To = 1 / (ta + tb) It should be noted that the times ta and tb are the times when the changeover contacts of the changeover switch 62 are connected to the contacts 62a and 62b, respectively.

The time ta and tb will be described.

That is, now, the integrated voltage signal ec of the operational amplifier 64 at time ta is ec (ta), the integrated voltage signal ec of the operational amplifier 64 at time tb is ec (tb), the resistance value of the resistor 63 is R1, the capacitance of the capacitor 65 is When the value is C1, the integrated voltage signal ec (ta) is expressed by the following equation.

Therefore, the time ta is given by the following equation.

ta = (− ec (ta) · R1 · C1) / eq As is apparent from (b) of FIGS. 5 (a) and 5 (b), the integrated voltage signal ec (ta) is the inverted reference voltage from the reference voltage signal er. Since the voltage falls to the signal −er, the voltage change is 2er. Therefore, if −ec (ta) = 2e is set, the time ta is determined by the following equation.

ta = (2er · R1 · C1) / eq (12) Similarly for time tb, Therefore, the time tb is given by the following equation.

tb = (ec (tb) · R1 · C1) / − (− eq) Here, when ec (tb) = 2er is set, the time tb is determined by the following equation.

tb = (2er · R1 · C1) / eq. (14) By the way, since the frequency fq of the frequency signal fq from the voltage-frequency conversion unit 6 is 1 / (ta + tb), the above equation (12), ( 1
Substituting 4), the frequency fq of the frequency signal fq becomes

fq ＝ eq / (4er ・ R1 ・ C1) (15) Substituting equation (8) into equation (15) gives This expression (16) is an expression when the reference voltage signal er is fixed as in the conventional voltage-frequency conversion unit 105, and the frequency component ω is not removed.

Next, by substituting the equation (9) into the equation (15), the following equation is obtained.

Here, since ω = 2πf and f = fv, the frequency
fq is as follows.

As is clear from this equation (18), K1, K2, π, fr, Vr, R1,
Since all of C1 are constants, the frequency fq of the frequency signal fq output from the voltage-frequency conversion unit 6 is not affected by the frequency fluctuation and represents a frequency exactly proportional to the reactive power VI sin θ.

In summary, in the present reactive energy meter, the first delayed voltage signal eva obtained by delaying the phase of the first voltage signal ev from the voltage detection unit 1 by π / 2 and the second voltage signal from the current detection unit 2 are used. It is multiplied by ei and supplied to the voltage-frequency conversion unit 6 to form the power-multiplied voltage signal eq, and at the same time the ev frequency of the first voltage signal from the reference voltage generation unit 5, that is, the load voltage V frequency. The reference voltage signal er in inverse proportion to the voltage-frequency conversion unit 6
And the power-multiplied voltage signal eq is divided by the reference voltage signal er in the voltage-frequency conversion unit 6 to be converted into the frequency signal fq proportional to the reactive power, and the frequency component f = fv is not included,
It outputs a frequency signal fq that is not affected by frequency fluctuations.

That is, the frequency f = output from the reference voltage generator 5
The fluctuation of the maximum amplitude generated in the delay unit 3 is removed by the reference voltage signal er inversely proportional to fv. Therefore, the reactive power can be accurately measured without being affected by the frequency variation of the load voltage V. As a result, the same reactive watt-hour meter can be used in both areas without being affected by the frequency even in areas where the frequency of the power source is 50 Hz or 60 Hz, and there are two types depending on the area where the conventional frequency is different. It is possible to eliminate the complexity of designing and manufacturing the reactive energy meter, the increase in manufacturing process, and the like.

Although the above embodiment is applied to the single-phase two-wire type reactive energy meter, the present invention is not limited to the single-phase two-wire type, and the voltage detecting unit 1, the current detecting unit 2, By providing a plurality of delay units 3, power multiplication units 4 and the like, it is also applicable to a multi-phase reactive energy meter. Since the reactive power of the multi-phase reactive energy meter is the sum of the reactive power of each phase, the voltage signal proportional to the load voltage of each power supply line is ev1, ev2, ~ evn, and the load current of each power supply line is The proportional voltage signals are ei1, ei2, ~ ein,
When the constants of proportionality are K1, K2, and Kn, the reactive energy amount Qo is expressed by the following equation.

Qo ＝ K1 ・ ev1 ・ ei1 ＋ K2 ・ ev2 ・ ei2 ＋… ＋ Kn ・ evn ・ ein…
(19) Therefore, if the outputs of the respective multiplication circuits that have undergone the signal processing as in the above embodiment are combined and added, the reactive power Qo that satisfies the expression (19) can be obtained.

FIG. 6 is a block diagram showing another embodiment of the present invention applied to a polyphase reactive energy meter. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals.

In this embodiment, as described above, the voltage detection unit 1, the current detection unit 2, the delay unit 3, and the power multiplication unit 4 are provided in plurality, and the respective power multiplication voltage signals eq are added by the addition unit 7 to obtain the voltage − It is supplied to the frequency conversion unit 6. Even in the multi-phase type, the frequency of each phase is the same, so the reference voltage generator 5
Generates a reference voltage signal er according to the frequency of the first voltage signal ev of the arbitrary voltage detection unit 1 and supplies it to the voltage-frequency conversion unit 6. The multi-phase reactive energy meter configured in this way can also achieve the same effects as in the first embodiment.

Furthermore, the present invention is not limited to the above embodiments.
For example, in each of the above embodiments, the first voltage signal ev is input to the reference voltage generator 5 to form the reference voltage signal er at the frequency of the first voltage signal ev. The delay voltage signal eva of 1 is input to the reference voltage generator 5, and the reference voltage signal er is input according to the frequency of the first delay voltage signal eva.
May be formed.

As described above, according to the present invention, one of the first and second voltage signals, which is proportional to the voltage and the current supplied to the load, is delayed, and the delayed voltage signal and the other are delayed. Form a voltage signal proportional to the reactive power based on the non-delayed voltage signal, and form a reference voltage inversely proportional to the frequency of the first or second voltage signal. Since the signal of the frequency proportional to the reactive power is generated based on the proportional voltage signal, the reactive power can be accurately measured without being affected by the frequency fluctuation of the power supply, and it is possible to measure the reactive power for each area with different frequencies. Since there is no need to design and manufacture multiple reactive energy meters in
Economical design can be achieved without increasing the number of designing and manufacturing processes and complicating it.

[Brief description of drawings]

FIG. 1 is a block diagram of a reactive energy meter according to an embodiment of the present invention, FIG. 2 is a detailed block diagram of a reference voltage generator used in the reactive energy meter of FIG. 1, and FIG. FIG. 2 is a waveform diagram showing the operation of the reference voltage generator, FIG. 4 is a detailed configuration diagram of the voltage-frequency converter used in the reactive energy meter of FIG. 1, and FIG. 5 is the voltage of FIG. FIG. 6 is a waveform diagram showing the operation of the frequency converter, FIG. 6 is a configuration diagram of another embodiment of the present invention, FIG. 7 is a configuration diagram of a conventional reactive energy meter, and FIG. 8 is a reactive energy amount of FIG. It is a waveform diagram explaining the operation of the meter. 1 ... Voltage detection unit, 2 ... Current detection unit, 3 ... Delay unit 4 ... Power multiplication unit, 5 ... Reference voltage generation unit 6 ... Voltage-frequency conversion unit

Claims (1)

[Claims] 1. A voltage detecting means for detecting a voltage supplied to a load and generating a first voltage signal proportional to the voltage, and a current supplied to the load for detecting a second voltage proportional to the current. Current detecting means for generating the voltage signal, delay means for delaying one of the first and second voltage signals by a predetermined phase angle, a delay output signal from the delay means, and the first and second voltage signals. Power multiplying means for outputting a voltage signal proportional to the reactive power based on the other voltage signal, and reference voltage generating means for generating a reference voltage inversely proportional to the frequency of the first or second voltage signal, A reactive energy meter, comprising: a voltage-frequency conversion means for generating a signal having a frequency proportional to the reactive power based on the voltage signal from the power multiplication means and the reference voltage.