JPH04324373A - Electronic watthour meter - Google Patents

Abstract

PURPOSE:To obtain an electronic watthour meter which can measure electric energy accurately without measuring an excess of electric energy even when a power change occurs. CONSTITUTION:A level judging circuit 3 compares an output signal of an auxiliary transformer 1 with a reference voltage and transmits an output signal of the auxiliary transformer 1 to a pulse width modulation circuit 41 only when the signal exceeds the reference voltage. The output signal and an output signal of an auxiliary current transformer 1 are multiplied with a multiplier circuit 42 thereby obtaining electric energy.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electronic watthour meters.

0002

2. Description of the Related Art A conventional electronic watt-hour meter operates as follows.

That is, the pulse width modulation circuit uses an auxiliary transformer (hereinafter referred to as
PT) converts the output signal into a pulse width duty cycle. The output signal of an auxiliary converter (hereinafter referred to as OT) that converts into a signal proportional to the current consumption of the distribution line is selectively taken in by a group of analog switches controlled by the output signal of the pulse width modulation circuit, and this signal and PT Time division multiplication is performed with the output signal of . The voltage-frequency converter integrates the output signal of the power-voltage converter and converts it into a pulse frequency,
This pulse signal is weighted by a frequency dividing circuit and the amount of power is displayed on the display section.

0004

[Problems to be Solved by the Invention] When such a conventional electronic watt-hour meter is used in a power plant or the like, the voltage gradually changes and fluctuations occur when a generator is started or stopped. At this time, even electric power below a certain voltage, which should not be measured, was sometimes measured. SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic watt-hour meter that operates at a predetermined voltage level or higher and can reliably measure electric energy even when voltage fluctuations occur. [Structure of the invention]

[0005]

[Means for Solving the Problems] In order to achieve the above objects, the present invention provides a transformer that outputs a signal proportional to the load voltage of a distribution line, and a current transformer that outputs a signal proportional to the current consumption of the distribution line. a level determination circuit that compares the output signal of the transformer with a reference voltage and conducts the output signal of the transformer when the voltage exceeds a predetermined value; a power-voltage converter that multiplies the output signal of the current transformer and the output signal of the converter, which are taken in from the switching means that performs opening and closing operations based on the output signal of the converter; Consists of a voltage-frequency converter that integrates the output signal of the converter and converts it into a pulse frequency, and a frequency divider that weights the output pulses of the voltage-frequency converter and outputs a pulse signal proportional to the amount of power. .

[0006]

[Operation] In such a configuration, the level judgment circuit compares the signal proportional to the load voltage from the transformer with the reference voltage, and when the signal is equal to or higher than a predetermined value, sends the output signal of the transformer to the converter, and the electric power - A voltage converter multiplies the output signal of the converter by a signal proportional to the current consumption output by the current transformer, and the frequency divider circuit integrates this multiplied signal and converts it into a pulse frequency. Since the amount of electric power is obtained by the method, the amount of electric power can be reliably measured without measuring the extra amount of electric power due to voltage fluctuations.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that descriptions of the same components as in the prior art will be omitted.

FIG. 1 is a block diagram of an electronic watt-hour meter of the present invention, and FIG. 2 is a block diagram of a level determination circuit of the electronic watt-hour meter of the present invention. In FIG. 1, the level discrimination circuit 3 has P
The output signal of T1 is compared with a reference voltage, and if the output signal of PT1 is higher than the reference voltage, the output signal of PT1 is sent to the pulse width modulation circuit 41 of the power-voltage converter 4. Of course, the pulse width modulation circuit 41 may be configured separately from the power-voltage converter 4. The multiplication circuit 42 multiplies the output signal of the CT2 and the output signal of the pulse width modulation circuit 41. The frequency dividing circuit 6 weights the integrated multiplication signal input via the voltage-frequency converter 5, and uses this signal to
A display drive circuit (not shown) is operated to display the amount of electric power.

FIG. 2 shows a configuration diagram of the level determination circuit 3. In FIG. 2, the level discrimination circuit 3 includes a peak hold circuit 31, a level comparator 32, and an analog switch 3.
Consists of 3.

In the peak hold circuit No. 31, the diode and capacitor are composed of a buffer amplifier, and P
Detect the peak of the AC signal ei output from T1. 32
is a comparator that outputs an output signal when a voltage of a certain level or higher is input, and 33 is an analog switch controlled by the output signal of the comparator 32. The peak value ei' (2ei) of the AC signal ei is detected by the peak hold circuit 31, and the peak value e is detected by the comparator 9.
Compare i with reference voltage er. ei ´≧er
In this case, the comparator 9 outputs a signal, which closes the analog switch 10 and sends the signal ei to the pulse width modulation circuit 41.

Further, when ei'<er, the output signal of the comparator 9 becomes "0" and the analog switch 10
By opening the signal ei, the signal ei is not input to the pulse width modulation circuit 41. Therefore, the electricity meter will not measure the amount.

0012

As described above, the present invention compares the output signal of the transformer with the reference voltage using the level discrimination circuit, and when the voltage exceeds a predetermined value, sends the output signal of the transformer to the converter.
To provide an electronic watt-hour meter that can reliably measure the amount of power without measuring excess power even when voltage fluctuation occurs, since the output signal of the transformer is not sent to the converter when the voltage is above a predetermined value. Can be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an electronic watt-hour meter of the present invention.

FIG. 2 is a configuration diagram of the level discrimination circuit shown in FIG. 1;

[Explanation of symbols]

3...Level discrimination circuit, 31...Peak hold circuit, 32...Comparator, 4...Power-voltage converter.

Claims (1)

[Claims] 1. A transformer that outputs a signal proportional to the load voltage of the distribution line, a current transformer that outputs a signal proportional to the current consumption of the distribution line, and a comparison between the output signal of the transformer and a reference voltage. a level discrimination circuit that conducts the output signal of the transformer when the output signal of the transformer is equal to or higher than a reference voltage; a power-to-voltage converter for multiplying the output signal of the current transformer by the output signal of the current transformer, which is taken in from a switch means that performs an opening/closing operation based on the output signal of the converter; A voltage-frequency converter that integrates the output signal of the voltage converter and converts it into a pulse frequency, and a frequency divider that weights the output pulses of the voltage-frequency converter and outputs a pulse signal proportional to the amount of electric power. An electronic electricity meter with