JPS6249937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic wattmeter, and more particularly to an electronic wattmeter that displays load current status in detail.

Generally, an electronic watt-hour meter includes a power frequency converter that generates a frequency proportional to electric power, and a counter that counts the output frequency of the converter. Since such an electronic watt-hour meter does not have a rotating disk like a conventional inductive watt-hour meter, a display means using a new circuit element is required to display the operating state of the meter.

Accordingly, an electronic watt-hour meter having a configuration as shown in FIG. 1 has been developed which satisfies the above-mentioned requirements.

In FIG. 1, 1 is a voltage converter that inputs the load voltage V _L , 2 is a current converter that inputs the load current I _L , and 3 is a multiplier that multiplies both signals from the voltage and current converters 1 and 2. The circuit 4 is an integrating circuit that converts the output of the multiplier circuit 3 into a pulse frequency proportional to the output of the multiplier circuit 3, for example. Reference numeral 5 denotes a frequency discrimination circuit for discriminating the output frequency of the integrating circuit 4, which includes a frequency comparison circuit 6, an oscillator 7 for creating a reference frequency for this circuit 6, and a frequency discriminator 7 for converting the frequency of this oscillator 7 into the reference frequency. A frequency divider circuit 8 and a gate circuit 9 having an AND function.
and a display section 10. Also, connected to the output section of the frequency discrimination circuit 5 are a frequency dividing circuit 11, a count display section 12, and an operation display section 13 such as an LED for displaying the operating state. In the above-mentioned watt-hour meter, when the load current I _L becomes less than a certain value, for example less than the starting current of the meter, the output frequency of the integrating circuit 4 is determined by the frequency comparison circuit 6 to be less than the reference frequency. As a result, the gate circuit 9 is closed, so that the so-called creep output is not counted by the count display section 12. Further, at this time, a signal indicating that the load current is less than the starting current is sent from the frequency comparator circuit 6 to the display section 10, indicating that the meter is not performing counting operation. In the case of conventional inductive instruments, this corresponds to when the disk does not rotate.

On the other hand, when I _L exceeds the starting current, the output of the integrating circuit 4 becomes higher than the reference frequency of the frequency dividing circuit 8, which opens the gate circuit 9 and causes the counting display section 12 to perform a counting operation. Display the count value. At this time, the display unit 10 displays information that the output of the integrating circuit 4 is higher than a certain standard to the comparing circuit 10.
The weighing operation is displayed by receiving the data from.

At this time, the magnitude of the load is determined from the pulse blinking frequency by the status display unit 13 connected to the output of the gate circuit 9.

Next, a specific example of the frequency discrimination circuit 5 will be explained with reference to FIG. In the figure, 21 is an input terminal to which the output frequency pulse ₁ of the integrating circuit 4 of FIG. 1 is input, 22 is an output terminal connected to the frequency dividing circuit 11,
23 and 24 are flip-flop circuits, 25 is an inverter circuit, and 26 is a counter for counting the output of the frequency dividing circuit 8. The output of this counter 26 is displayed on a display 28 via a flip-flop circuit 27. Further, ₃ indicates a reference frequency pulse to the comparator circuit 6.

Now, the case where ₁ ≦ ₃ will be explained. Pulse ₁ of a predetermined frequency output from the integrating circuit 4
enters the set terminal S of the flip-flop circuit 23 via the terminal 21, and the output terminal Q of the flip-flop circuit 23
23 outputs a "1" signal. However, pulse ₁ is inverted by inverter circuit 25 and clocked at the clock input terminal of subsequent flip-flop circuit 24.
Since it is input to CK as a “0” signal, circuit 2
The output terminal Q24 of No. 4 remains the "0" signal and does not change. Therefore, the gate circuit 9 remains closed. Further, since pulse ₁ enters the reset terminal R of the counter 26, the counting contents are cleared, and then counting of pulse ₃ from the frequency dividing circuit 8 is started. When pulse ₁ falls, inverter circuit 25
The signal is inverted and input to the clock input terminal CK of the flip-flop circuit 24, so that the output terminal Q24 of the flip-flop circuit 24 outputs a "1" signal.
This "1" signal transmission period lasts for a period of time until an output from the output terminal C of the counter 26 counting the pulses ₃ from the frequency dividing circuit 8 is output. Since there is no next pulse input during this period, no output pulse appears at the output of the gate circuit 9. When a pulse is output from output terminal C, flip-flop circuit 2
Since gates 3 and 24 are reset, the gate circuit 9 remains closed thereafter.

At this time, the output of the output terminal C of the counter 26 is input to the set terminal S of the flip-flop circuit 27, and at this time, the output of the gate circuit 9 becomes "0" and the display 28 indicates that there is no measurement. The above operation is shown in the time chart of FIG.

Next, when ₁ > ₃ , that is, when the load current is above a predetermined value, the gate circuit 9 is opened and the flip-flop circuit 27 is reset, so the display 28 does not display any operation. Instead, the status display section 13 in FIG. 1 performs a blinking operation to display the operating status.

However, with the above electronic watt-hour meter, when the watt-hour meter is connected to a circuit that generates power flow,
The following inconveniences occur. That is, large electricity consumers may have their own power generating equipment, and when there is a surplus of electricity, they may supply electricity to the electric power company, contrary to normal practice. This is called power flow.

By the way, in a conventional watt-hour meter, the state of the load current is: when the power flow is in the opposite direction, when the power flow is in the forward direction but less than the starting current of the meter,
There are cases where the power flow is in the positive direction and is higher than the starting current, and it is impossible to distinguish between these using conventional meters.

That is, when the display 28 of FIG. 2 operates, the output of the frequency dividing circuit 4 is below a predetermined frequency;
If the load current for this purpose is in the opposite direction, an inconvenience arises in that the frequency divider circuit 4 may not generate an output.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an electronic watt-hour meter that can distinguish and display the above-mentioned load conditions, thereby improving monitoring efficiency. It is something.

An embodiment of the present invention will be described below with reference to FIG. In this figure, the same parts as in FIGS. 1 and 2 will be described with the same reference numerals.
First, in the electronic watt-hour meter of the present invention, a voltage signal proportional to the load voltage V _L converted by the voltage converter 1 and a current signal proportional to the load current I _L converted by the current converter 2. is multiplied by a multiplier circuit 3 to obtain electric power, and then converted into a pulse ₁ with a frequency proportional to the magnitude of _the electric power by a subsequent integrating circuit 4. The pulse ₃ of the reference frequency thus obtained is compared, and when the frequency of the pulse ₁ caused by the load current I _L is lower than the reference frequency, the gate circuit 9 is closed and the display section 12 is put into a non-display state, and both of the above-mentioned frequencies are The configuration in which the gate circuit 9 is closed and the display section 12 is in a non-display state when the frequencies are reversed, and the gate circuit 9 is opened and the count value is displayed on the display section 12 when the above two frequencies are reversed is the same as that in FIG. be.

A particular difference between FIG. 4 and FIGS. 1 and 2 is that the display section 10 has been improved.
In other words, this display unit 10 includes displays 32a to 32c corresponding to a plurality of gate circuits 31a to 31c having an AND function, and also displays the outputs of the flip-flop circuit 27 that are supplied to these gate circuits 31a to 31c. is controlled by the output of a level detection circuit 33 that detects the output level of the multiplier circuit 3, and the indicators 32a to 32a are displayed depending on the state of the load current.
32c is selectively displayed. 3
4 is an inverter circuit.

Next, the operation of the electronic watt-hour meter configured as described above will be explained. First, when the load current I _L flows in the opposite direction (at the time of reverse power flow), the output of the multiplier circuit 3 becomes a negative output. This negative output is detected by the level detection circuit 51 and outputs a "1" signal. On the other hand, since the output of the multiplier circuit 3 becomes negative, the output of the integrator circuit 4 becomes zero ( ₁ < ₃ in FIG. 3), and a "1" signal is output from the output terminal Q27 of the flip-flop circuit 27. . As a result, gate circuit 3
A “1” signal appears at the output of 1a, and the display 32a
is displayed (reverse power flow display).

Next, when ₁ ≦ ₃ , that is, the load current I _L
is in the positive direction and is less than the starting current, as described above, the output terminal Q27 of the flip-flop circuit 27
Since the load current I _L is in the positive direction, the output of the multiplier circuit 3 becomes greater than zero, so the output of the level detection circuit 33 becomes a “0” signal, which is output by the inverter circuit 34. It is inverted and becomes "1". As a result, gate circuit 31b
The indicator 32b will operate via (forward direction, non-quantity meter).

In addition, in the case of ₁ > ₃ , that is, the load current I _L
is in the positive direction and is above a certain value, the output of the inverter circuit 34 is "1", the output terminal Q27 of the flip-flop circuit 27 is "0", that is, the output terminal 27 becomes "1", and the gate circuit 3
1c opens the gate and the indicator 32c operates (forward direction operation).

Note that the present invention is not limited to the above embodiments. In FIG. 4, the level detection circuit 33 determines whether the output of the multiplier circuit 3 is positive or negative based on zero, but the output of the multiplier circuit 3 is compared with, for example, a negative reference voltage (e.g. e _R ). The configuration may be such that it is determined that the load current I _L is in the opposite direction when is equal to or less than -e _R . Further, each of the displays 32a to 32c can be arranged in an arrangement as shown in FIG. 5, for example, to facilitate monitoring.
Further, as shown in FIG. 6, it is also possible to integrate the display on the display section 13 and the display on the display 32c via a gate circuit 36, and to make the display 32c' blink. In addition, various modifications can be made to the present invention without departing from the spirit thereof.

As described in detail above, according to the present invention, it is possible to distinguish and display the load current depending on the state of the load current, so that the power usage state can be easily checked and monitoring efficiency can be improved. In addition, we provide an electronic watt-hour meter that allows you to check the direction of applied voltage and current when testing the watt-hour meter, and also allows you to easily perform a self-check (function check) of the watt-hour meter itself using the three displays mentioned above. can.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a general electronic watt-hour meter, Fig. 2 is a diagram showing an example of the frequency discrimination circuit shown in Fig. 1, Fig. 3 is a time chart showing the operation of Fig. 2, and Fig. 4 is a diagram showing a circuit example of the frequency discrimination circuit shown in Fig. 1. The figure is a block diagram showing one embodiment of an electronic watt-hour meter according to the present invention, and FIGS. 5 and 6 are diagrams showing modified examples of the present invention. DESCRIPTION OF SYMBOLS 1... Voltage converter, 2... Current converter, 3... Multiplier circuit, 4... Integrator circuit, 5... Frequency discrimination circuit, 6... Frequency comparison circuit, 7... Oscillator, 8... Frequency dividing circuit, 9...
Gate circuit, 10...display section, 12...count display section,
13...Operation display section, 27...Flip-flop circuit, 31a-31c...Gate circuit, 32a-32
c, 32c'...Display device, 33...Level detection circuit.

Claims (1)

[Claims] 1 a multiplier circuit that generates a signal proportional to power;
A conversion circuit that converts the output signal of this multiplier circuit into a frequency signal proportional to this, a gate circuit connected to the output side of this conversion circuit, a reference frequency generator that outputs a reference frequency, and this reference frequency generator. a comparison circuit that compares the output frequency of the conversion circuit and the output frequency of the conversion circuit, a level detection circuit that detects the output level of the multiplication circuit, and a plurality of gate circuits that compare the output of this circuit and the output of the comparison circuit; The display device is provided with a display connected to each of these gate circuits and selectively displayed according to a signal caused by the comparison circuit and an output signal of the level detection circuit, so that the display can be distinguished and displayed according to the state of the load current. An electronic watt-hour meter characterized by: