JPH01239474A - Electronic watthour meter - Google Patents

Abstract

PURPOSE:To simplify the constitution of an electronic watthour meter by removing a necessity to synchronize between each signal in such a manner that only effective components of the signals proportional to a load voltage of a feeder and a load current of the feeder are converted to DC voltages then to a digital value. CONSTITUTION:By an auxiliary transformer 1, the signal proportional to the load voltage of the feeder is supplied to a 1st input terminal 10a on a rectified current smoothing circuit 9, and by an auxiliary current transformer 2, the signal proportional to the load current of the feeder is supplied to a 2nd terminal 10b on an effective current detecting circuit 10. In the circuit 9, the input signal is converted to the DC voltage and supplied to a 1st channel input terminal 15a on an A/D converter circuit 15, and in the circuit 10, the effective component having the same phase as that of the input signal supplied to the 1st input terminal 10a is converted to the DC voltage and supplied to a 2nd channel input terminal 15b on the circuit 15. The the DC voltages supplied to the terminals 15a and 15b are gradually converted from A to D, and the electric energy is computed by a specified computation of the data in an arithmetic part 17, then displayed on a display part 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an electronic watt-hour meter that employs a microcomputer.

"Prior Art" FIG. 2 is a block diagram of a conventional electronic watt-hour meter that employs a microcomputer. In the figure, 1 is an auxiliary transformer, and 2 is an auxiliary current transformer, each of which supplies a signal proportional to the load voltage of the power supply line and a signal proportional to the load current of the power supply line to the sample and hold circuit 3.4. The sample and hold circuit 3.4 samples and holds the instantaneous value of the input signal at a cycle faster than the cycle of the input signal. The sampled and held input signal is sent to the A/D conversion circuit 5.6.
After each is converted into a digital value, it is taken into the calculation section 7, subjected to predetermined calculation processing, and displayed on the display section 8.

"Problem to be Solved by the Invention" In the prior art as described above, the A/D conversion circuit 5.
Since the signal inputted to the circuit 6 is an instantaneous value having both magnitude information and phase information, synchronization between the signals is required, and therefore a sample and hold circuit 3.4 is required. Also, since the sign of the signal has a (+) sign and a (=) sign, this A
The /D conversion circuit 5.6 needs to use a bipolar type A/D converter.

In general, data must be input to the calculation unit 7 at a cycle faster than the input signal cycle, and the calculation process is also complicated.

In view of this point, the present invention eliminates the need for a sample and hold circuit, simplifies the circuit by using a unipolar A/D converter, and allows mixing by simple arithmetic processing.

"Means for Solving the Problem" Only the effective components of the input signal proportional to the load voltage of the power supply line and the signal proportional to the load current of the power supply line are converted into DC voltage, and then converted into digital values.

"Operation" According to the present invention, the signal input to the A/D conversion circuit is converted into a direct current. Therefore, there is no need for synchronization between signals when performing digital conversion, and a sample and hold circuit is not required. In addition, the sampling period can be slow, and since the input signal proportional to the load current of the power supply line contains only the effective component, there is no need to calculate the power factor in the calculation section, and the calculation processing is simple. An inexpensive microcomputer can be used.

"Example" Embodiments of the present invention will be described in detail below based on the drawings.

Note that the same parts as those in the above-mentioned prior art are given the same numbers, and the explanation thereof will be omitted.

FIG. 1 is a block diagram of an electronic watt-hour meter showing an embodiment of the present invention. In this figure, 9 is a rectifying and smoothing circuit to which a signal from the auxiliary transformer 1 is supplied to an input terminal 9a;
is an active current detection circuit in which the signal from the auxiliary transformer 1 is supplied to a first input terminal 10a, and the signal from the auxiliary current transformer 2 is supplied to a second input terminal 10b. Also 15
17 is an A/D conversion circuit to which the voltages from the DC smoothing circuit 9 and the active current detection circuit 10 are supplied to input terminals 15a and 15b, respectively; It is a calculation section that performs calculation processing to calculate the amount of electric power.

Next, the operation of the above embodiment will be explained.

The auxiliary transformer 1 supplies a signal proportional to the load voltage of the power supply line to the input terminal 9a of the rectifying and smoothing circuit 9 and the first input terminal 10a of the active current detection circuit 10.

The auxiliary current transformer 2 supplies a signal proportional to the load current of the power supply line to the second input terminal 10b of the active current detection circuit 10. The rectifying and smoothing circuit 9 converts the signal supplied to the input terminal 9a into a DC voltage and supplies it to the first channel input terminal 15a of the A/D conversion circuit 15. The active current detection circuit 10 converts the in-phase component (active component) of the signal supplied to the first input terminal 10a of the input signal supplied to the second input terminal 10b into a DC voltage, The signal is supplied to the second channel input terminal 15b of the /D conversion circuit 15.

The A/D conversion circuit 15 is a unipolar type A/D converter because the voltage supplied to the input terminals 15a and 15b is a DC voltage.
A D converter may be used as long as it has the required number of input terminals.

The A/D conversion circuit 15 receives a channel number and a command from the calculation unit 17 through a control line (not shown), and sequentially converts the DC voltages supplied to the input terminals 15a and 15b into an A/D converter.
The data is converted and taken into the calculation unit 17.

The arithmetic unit 17 performs predetermined arithmetic processing on the captured data to calculate the amount of power and displays it on the display unit 8 .

The arithmetic processing carried out by the arithmetic unit 17 is a DC signal arithmetic operation, and there is no need for a power factor arithmetic operation, so that it can be completed with extremely simple arithmetic operations.

Therefore, an inexpensive microcomputer may be used as the arithmetic unit 17.

``Effects of the Invention'' As detailed above, according to the present invention, the sample-and-hold circuit is omitted, a unipolar A/D converter can be used, the circuit is simplified, and the circuit is simplified by simple arithmetic processing. We can provide electronic energy meters.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electronic watt-hour meter showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional electronic watt-hour meter. In the figure, reference numeral 9 indicates a rectifying and smoothing circuit 10, an effective current detection circuit 15, and an A/D conversion circuit 17, which are arithmetic units.

Claims (1)

[Claims] a rectifying and smoothing circuit that converts a signal proportional to the load voltage of the power supply line into a DC voltage; an active current detection circuit that detects an active component of the signal proportional to the load current of the power supply line and converts it into a DC voltage; An A/D conversion circuit that digitally converts the DC voltage output from the current detection circuit and the rectifying and smoothing circuit, and a predetermined calculation process is performed on the digital data taken in from this A/D conversion circuit to calculate the amount of electric power. An electronic watt-hour meter characterized by comprising a calculation section that performs the following operations.