JPH0361865A - Electronic watthour meter - Google Patents

Abstract

PURPOSE:To simplify the measurement of watthours for two kinds of commercial power-source frequencies by selecting first and second correcting coefficient signals with a correcting-coefficient selecting circuit in response to a judged signal, multiplying the selected signal by a correcting coefficient with respect to a voltage signal, and performing the correction. CONSTITUTION:A period with respect to voltage fluctuation detected with an auxiliary transformer 1 is sent into a central control part 12 as a digital signal. Then, the control part 12 judges whether the power source frequency is 50Hz or 60Hz. The judged signal is outputted to a correcting coefficient selecting circuit 13. In this circuit, the correcting signal supplied from a correcting circuit 9 is multiplied by a coefficient corresponding to 50Hz or 60Hz. Either of the first or second correcting coefficient signal corresponding to 50Hz to 60Hz is outputted to a voltage/frequency conversion circuit 14. In this circuit 14, the voltage signal from an adding circuit 7 is corrected based on either the first or second correcting coefficient signal, and the voltage signal is converted into the frequency signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic watt-hour meter that measures and displays electric energy.

[Conventional technology]

FIG. 2 is a block diagram showing a schematic configuration of a conventional electronic watt-hour meter. To explain this operation, first, the auxiliary transformer (PT) 1.3 converts a voltage signal proportional to the load voltage of the distribution line (not shown) into a power/voltage conversion circuit (pulse width modulation time division multiplication circuit). 5.6, and the auxiliary current transformer (C
T) 2.4 also outputs a current signal proportional to the consumption current of the distribution line, that is, the load current, to the power/voltage conversion circuits 5 and 6.

The power/voltage conversion circuits 5 and 6 multiply the value of these voltage signals and the value of the current signal to determine the amount of power. Voltage signals from the power/voltage conversion circuit 5 . 6 corresponding to this amount of power are added in an adding circuit 7 and then output to a voltage/frequency conversion circuit 8 .

The voltage/frequency conversion circuit 8 converts the voltage signal corresponding to this amount of electric power into a frequency signal, but at this time, the correction circuit 9
A predetermined amount of correction is performed on this voltage signal based on a correction coefficient signal from.

To briefly explain the reason for performing this predetermined amount of correction, the amount of electric power is generally expressed as the product of a predetermined coefficient whose denominator includes a component of the angular frequency ω of the power supply voltage and a sine function of the phase angle ωt. . When converting a voltage signal corresponding to the amount of electric power into a frequency signal, it is necessary to eliminate the component of the angular frequency ω included in the denominator. In order to perform this cancellation, the frequency correction circuit 8 attempts to multiply the component of the angular frequency ω by a correction coefficient corresponding to the component.

That is, there are two types of frequencies of the power supply voltage (the frequency of the load voltage is also the same): a first frequency of 50 Hz and a second frequency of 60 Hz. Now, assuming that the frequency of the power supply voltage is 50 Hz, the correction circuit 9 outputs a correction coefficient signal corresponding to this 50 Hz,
Correction is performed on the voltage signal from the adder circuit 7.

Then, the voltage/frequency conversion circuit 8 converts this corrected voltage signal into a frequency signal.

The central control unit 10 controls the display unit based on this frequency signal.
1 performs control for displaying the electric energy.

[Problem to be solved by the invention]

The electronic watt-hour meter shown in FIG. 2 is used in areas where the commercial power frequency is 50 Hz, and the correction circuit 9 is designed to output only a correction coefficient signal corresponding to 50 Hz.

In other words, the correction circuit 9 has a hardware configuration exclusively for 50Hz, and when producing an electronic watt-hour meter for use in an area where the commercial power frequency is 60Hz, the correction circuit 9 must be designed specifically for 60Hz. Need to change.

Therefore, conventionally, two types of electricity meters had to be produced, one with a commercial power supply frequency of 50Hz and one with a commercial power supply frequency of 60Hz, and the production process or management process had to be divided into two types accordingly. It was no longer possible.

Honbakucho was created in view of the above circumstances, and its purpose is to provide an electronic watt-hour meter that can be used for either of the two types of commercial power supply frequencies. .

[Means to solve the problem]

As a means for solving the above problems, the present invention includes a determining means for determining which frequency the load voltage is at, out of the first frequency or the second frequency, and according to a determining signal from the determining means, a correction coefficient selection circuit that selects a first or second correction coefficient signal corresponding to the first or second frequency;
The configuration includes a voltage/frequency conversion circuit that performs correction by multiplying a voltage signal by a correction coefficient based on the signal selected by the correction coefficient selection circuit.

[For production]

In the above configuration, the determining means determines under which frequency of the first or second frequency the pre-meal voltage is located,
The determination signal is output to the correction coefficient selection circuit.

Based on this discrimination signal, the correction coefficient selection circuit selects the first or second correction coefficient signal corresponding to the first or second frequency and outputs it to the voltage/frequency conversion circuit.

The voltage/frequency conversion circuit 1 corrects the voltage signal by multiplying it by a correction coefficient using this signal, and then converts the corrected voltage signal into a frequency signal.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

The central control unit 12 as a determination means has a power supply frequency of 5
A detection signal is provided as to whether the frequency is 0 Hz or 60 Hz. This detection signal, for example, indicates the period related to the voltage fluctuation detected by the auxiliary transformer 1.
The information may be sent to the central control unit 12 as a digital signal.

The central control unit 12 determines whether the power supply frequency is 50 Hz or 60 Hz based on this detection signal, and outputs the determination signal to the correction coefficient selection circuit 13.

The correction coefficient selection circuit 13 is supplied from the correction circuit 9 based on this determination signal. +ti positive signal, 50H
Multiply by a certain factor corresponding to z or 60Hz. and,
Either the first or second correction coefficient signal corresponding to 50 Hz or 60 Hz is output to the voltage/frequency conversion circuit 14.

The voltage/frequency conversion circuit 14 corrects the voltage signal from the addition circuit 7 based on either the first or second correction coefficient signal, and converts the corrected voltage signal into a frequency signal.

In the case of this embodiment, the correction circuit 9 is a circuit dedicated to 50 Hz, similar to that used in FIG. Therefore, when the central control unit 12 determines that the frequency is 50 Hz, the correction coefficient selection circuit 13 passes the correction signal from the correction circuit 9 as it is (same as multiplying it by a coefficient 1) and outputs it as the first correction coefficient signal. can,
Only in the case of 60 Hz, the second correction coefficient signal can be output by multiplying the coefficient of the correction signal from the correction circuit 8.

Next, the operation of this embodiment configured as above will be explained.

First, when a reset switch (not shown) is manually pressed, a power-on reset signal is sent to the central control section 12, and the central control section 12 is initialized.

Then, as in the case of FIG.
The auxiliary current transformer 2.4 also outputs a current signal proportional to the load current to the power/voltage conversion circuit 5.6. Electricity/*
The voltage conversion circuit 5.6 multiplies the value of these voltage signals and the value of the current signal to obtain the amount of electric power, and the voltage signal corresponding to this amount of electric power is sent to the voltage/frequency conversion circuit via the addition circuit 7. Output to 14.

On the other hand, as described above, the central control unit 12 determines whether the power supply frequency, that is, the frequency of the load voltage is 50 Hz or 60 Hz. Now, for example, the central control unit 12
It is assumed that the determination signal is determined to be Hz and the determination signal is output to the correction coefficient selection circuit 13.

Then, the correction coefficient selection circuit 13 outputs to the voltage/frequency conversion circuit 14 a second correction coefficient signal obtained by multiplying the correction signal from the correction circuit 9 by a coefficient corresponding to 60 Hz.

The voltage/frequency conversion circuit 14 corrects the voltage signal from the addition circuit 7 based on this second correction coefficient signal, and converts the corrected voltage signal into a frequency signal.

The central control unit 12 then controls the voltage/frequency conversion circuit 14
Control is performed to display the amount of electric power on the display unit 10 based on the frequency signal from.

In this way, the voltage/frequency conversion circuit 11 determines that the frequency of the load voltage is 50H before converting the voltage signal into a frequency signal.
z or 60 Hz, the voltage signal can be appropriately corrected. Therefore, this electricity meter can be applied to both areas where the commercial power supply frequency is 50 Hz and 60 Hz.

〔Effect of the invention〕

As explained above, according to the present invention, the determining means determines which of the first or second frequency the frequency of the load voltage is under, and the correction coefficient is determined based on this determination signal. Since the selection circuit outputs an appropriate correction coefficient signal to the voltage/frequency conversion circuit for correcting the voltage signal by multiplying the correction coefficient, It is possible to measure the amount of electric power, and it is possible to simplify the production process or management process.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure is a block diagram showing the configuration of a conventional example. 5.6...Power/voltage conversion circuit, 12...Discrimination means (central control unit), 13...Correction coefficient selection circuit, 14.
...Voltage/frequency conversion circuit.

Claims (1)

[Claims] The amount of electric power is determined by multiplying the value of the load voltage having the first or second frequency by the value of the load current, and a voltage signal corresponding to the amount of electric power is formed. correct the voltage signal by multiplying the first or second frequency by a correction coefficient, further convert the corrected voltage signal into a frequency signal, and calculate the amount of electric power based on the frequency signal. In an electronic watt-hour meter that performs display, a determining means for determining which frequency the load voltage is at, out of the first frequency or the second frequency, and a determining means for determining whether the load voltage is at the first frequency or the second frequency; a correction coefficient selection circuit that selects a first or second correction coefficient signal corresponding to the first or second frequency; and a correction that multiplies the voltage signal by the correction coefficient by the signal selected by the correction coefficient selection circuit. An electronic watt-hour meter characterized by comprising: a voltage/frequency conversion circuit that performs the following;