JP2733450B2 - Power failure detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power failure detection device for detecting the occurrence of a power failure in a single-phase AC voltage circuit at a high speed.

[0002]

2. Description of the Related Art As a conventional method for detecting a power failure occurring in a single-phase AC voltage circuit, a single-phase full-wave rectified waveform (detection in FIG. In general, the single-phase full-wave rectified waveform is further passed through a DC filter to be converted into a DC average value, and the level of the DC average value is compared with a power failure detection set value.

In this case, whether or not a power failure of the single-phase AC voltage has occurred is determined by monitoring whether or not the DC average value level has become lower than a power failure detection set value.

[0004]

However, in such a conventional method for detecting a power failure occurring in a single-phase AC voltage circuit, the average DC level value passed through a DC filter is lower than a power failure detection set value. Since the monitoring is performed by monitoring whether the error has occurred, the following problems have been encountered.

That is, in the single-phase full-wave rectified waveform rectified from the single-phase AC voltage waveform by the rectifier, a value indicating a DC average voltage or less occurs every cycle. For this reason, in order to perform averaging after the detection of the AC waveform, a DC filter having a large time constant is required, and this DC filter has a problem that the detection time when a power failure occurs is delayed.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a power failure detection device for detecting a power failure of a single-phase AC voltage at high speed.

[0007]

According to the first aspect of the present invention,
In a power failure detection device that detects a power failure of a single-phase AC voltage in a single-phase AC voltage circuit, a capacitor connected between the single-phase lines, a current transformer that detects a current flowing through the capacitor, and the single-phase AC voltage , A voltage waveform rectifier that performs single-phase full-wave rectification on the detected waveform, a current waveform rectifier that performs single-phase full-wave rectification on the AC current detection waveform detected by the current transformer, the voltage waveform rectifier, and the current waveform rectifier A synthesizer that synthesizes a voltage waveform and a current waveform that are respectively rectified by a comparator, and a comparator that detects a power failure of the single-phase AC voltage by comparing a synthesized waveform synthesized by the synthesizer with a predetermined reference value. , Is provided.

[0008]

According to the first aspect of the present invention, in a power failure detection device for detecting a power failure of a single-phase AC voltage in a single-phase AC voltage circuit, a current flowing through a capacitor connected between the single-phase lines is converted to a current transformer. , The single-phase AC voltage is detected by a voltage waveform rectifier to perform single-phase full-wave rectification, and the AC current detection waveform detected by the current transformer is subjected to single-phase full-wave rectification by a current waveform rectifier. The voltage rectifier and the current waveform respectively rectified by the waveform rectifier and the current waveform rectifier are combined by a combiner, and a comparison circuit compares the combined waveform with a predetermined reference value to detect a power failure of the single-phase AC voltage. .

Therefore, by setting the discharge time determined by the capacity of the capacitor to be short, the composite waveform quickly falls below the power failure detection set value after the power failure occurs, and the power failure can be detected at high speed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below in detail with reference to FIGS. 1 and 2 are diagrams showing an embodiment of a power failure detection device to which the present invention is applied.

First, the configuration will be described. FIG. 1 is a diagram illustrating a circuit configuration of a power failure detection device connected to the single-phase AC voltage circuit 1. In this figure, a power failure detection device includes a transformer 2, a voltage waveform rectifier circuit 3, a capacitor 4, a current transformer 5, a current waveform rectifier circuit 6, a load resistor 7, a synthesizer 8, a power failure detection setting circuit 9, and a comparator 10. It consists of.

The transformer 2 outputs the single-phase AC voltage V supplied to the single-phase AC voltage circuit 1 to the voltage waveform rectification circuit 3 at a predetermined transformation ratio, and the voltage waveform rectification circuit 3 receives the input from the transformer 2. The obtained single-phase AC voltage V is full-wave rectified, and the single-phase full-wave rectified waveform Vs is output to the synthesizer 8.

The capacitor 4 has a certain capacitance and is connected between the lines of the single-phase AC voltage circuit 1, and has a single-phase AC voltage V
In proportion to the change in
Of the capacitor current Ic. The current transformer 5 detects a capacitor current Ic generated in the capacitor 4 and outputs the detected current to the current waveform rectifier circuit 6.

The current waveform rectifier circuit 6 performs full-wave rectification on the capacitor current Ic detected by the current transformer 5 and outputs the single-phase full-wave rectified waveform Ics to the synthesizer 8 through the load resistor 7. The load resistor 7 is a resistor that converts a detected current value of the capacitor 4 into a voltage. The combiner 8 outputs to the comparator 10 a combined waveform VI obtained by combining the single-phase full-wave rectified waveform Vs input from the voltage waveform rectifier circuit 3 and the single-phase full-wave rectified waveform Ics input from the current waveform rectifier circuit 6. I do.

The power failure detection setting circuit 9 is a circuit for setting a power failure set value Vr to be compared when a power failure is detected. The comparator 10 outputs the synthesized waveform V input from the synthesizer 8.
The level value of I is compared with the power failure set value Vr set by the power failure detection setting circuit 9, and when the level value of the composite waveform VI becomes lower than the power failure set value Vr, a power failure detection signal is output.

Next, the operation will be described.

First, the operation principle of the power failure detection device according to the present embodiment will be described. The capacitor current Ic flowing through the capacitor 4 connected between the lines of the single-phase AC voltage circuit 1 has a waveform whose phase is advanced by 90 degrees with respect to the single-phase AC voltage waveform. That is, the capacitor current Ic is represented by the following equation, where V is the single-phase AC voltage, f is the AC frequency, and C is the capacitance of the capacitor.

Ic = 2πf · C · V Here, if the frequency f and the capacitor C are constant, it is understood that the capacitor current Ic changes in proportion to the single-phase AC voltage V. When the single-phase full-wave rectified waveform Ics obtained by full-wave rectification of the capacitor current Ic and the single-phase full-wave rectified waveform Vs obtained by full-wave rectification of the single-phase AC voltage V are combined, a single-phase full-wave having a phase difference of 90 degrees is obtained. Waveform synthesis is performed. This composite waveform VI
Has less ripple component than a single-phase full-wave waveform and does not take a value below the single-phase full-wave DC average value. In the present embodiment, a power failure is detected by using the synthesized waveform, so that a conventional DC filter is unnecessary in principle.

Next, FIG. 1 shows an actual power failure detection operation.
The description will be made with reference to the timing charts of the signal waveforms of the respective units shown in FIG.

In FIG. 1, a single-phase AC voltage V (see FIG. 2A) supplied to a single-phase AC voltage circuit 1
, A full-wave rectified by the voltage waveform rectifier circuit 3 and a single-phase full-wave rectified waveform Vs (FIG. 2).
(See (c)) to the combiner 8.

A capacitor current Ic (see FIG. 2B) generated according to a change in the single-phase AC voltage V in a capacitor 4 connected between the lines of the single-phase AC voltage circuit 1 is supplied to a current transformer 5. , And is subjected to full-wave rectification by the current waveform rectifier circuit 6 and output to the combiner 8 via the load resistor 7 as a single-phase full-wave rectified waveform Ics (see FIG. 2D).

In the combiner 8, the single-phase full-wave rectified waveform Vs and the single-phase full-wave rectified waveform Ics are combined to form a combined waveform VI (FIG. 2).
(See (e)) is generated and output to the comparator 10. The comparator 10 compares the level value of the synthesized waveform VI input from the synthesizer 8 with a power failure detection set value Vr set by the power failure detection setting circuit 9 (see FIG. 2E).

For example, when a power failure occurs in the single-phase AC voltage V as shown in FIG. 2A, the composite waveform VI immediately becomes lower than the power failure detection set value as shown in FIG. The occurrence of a power failure is detected, and a power failure detection signal is output.

In the power failure detection device 1 according to the present embodiment, when the AC voltage V is interrupted, the electric charge accumulated in the capacitor 4 flows to the AC side or is consumed by the load resistance 7 of the current transformer 6. By setting the discharge time determined by the capacity of the battery to be short, the composite waveform VI quickly becomes equal to or less than the power failure detection set value Vr after the power failure occurs, and the power failure can be detected at a high speed.

Therefore, it is possible to detect a power failure of the single-phase AC voltage at a high speed without a time delay due to the DC filter as in the related art.

[0026]

According to the first aspect of the present invention, a current flowing through a capacitor connected between single-phase lines of a single-phase AC voltage circuit is detected by a current transformer, and the single-phase AC voltage is detected by a voltage waveform rectifier. And a single-phase full-wave rectifier, and an AC current detection waveform detected by the current transformer is subjected to single-phase full-wave rectification by a current waveform rectifier, and voltage waveforms rectified by the voltage waveform rectifier and the current waveform rectifier, respectively. And a current waveform are synthesized by a synthesizer, and the power failure of the single-phase AC voltage is detected by comparing the synthesized waveform with a predetermined reference value by a comparison circuit. Is set to a small value, the composite waveform quickly falls below the power failure detection set value after the power failure occurs, and the power failure can be detected at a high speed.

[Brief description of the drawings]

FIG. 1 is a circuit block configuration diagram of a power failure detection device to which the present invention is applied.

FIG. 2 is a timing chart of signal waveforms at various parts in the power failure detection device of FIG. 1;

FIG. 3 is a timing chart of signal waveforms for explaining a conventional process of detecting a power failure of an AC voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single-phase AC voltage circuit 2 Transformer 3 Voltage waveform rectifier circuit 4 Capacitor 5 Current transformer 6 Current waveform rectifier circuit 7 Load resistance 8 Synthesizer 9 Power failure detection setting circuit 10 Comparator

Claims (1)

(57) [Claims] 1. A power failure detection device for detecting a power failure of a single-phase AC voltage in a single-phase AC voltage circuit, comprising: a capacitor connected between the single-phase wires; a current transformer detecting a current flowing through the capacitor; A voltage waveform rectifier that detects the single-phase AC voltage and performs single-phase full-wave rectification on the detected waveform; a current waveform rectifier that performs single-phase full-wave rectification on the AC current detection waveform detected by the current transformer; A synthesizer that synthesizes a voltage waveform and a current waveform respectively rectified by a rectifier and a current waveform rectifier; and comparing the synthesized waveform synthesized by the synthesizer with a predetermined reference value to stop the power failure of the single-phase AC voltage. A power failure detection device, comprising: a comparison circuit for detecting the power failure.