JPS6323516A - Instantaneous interruption and open-phase detecting circuit for multiphase electric source - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an instantaneous power failure/open phase detection circuit for a multiphase power supply.

B1 Summary of the Invention The present invention provides a circuit that detects instantaneous power outages or phase loss from each phase voltage signal of a multiphase power supply by high-gain amplification of each phase voltage signal and logical processing of absolute value waveforms. By detecting the phase, it can be detected reliably and easily.

C0 Conventional technology Uninterruptible power supplies and inverters often use three-phase power as a power source, but when there is a momentary power outage or voltage drop (hereinafter referred to as an instantaneous power outage), or when one phase of the power supply voltage drop (hereinafter referred to as open phase).

In some cases, it is desirable to be able to reliably detect these instantaneous power outages and phase failures in order to protect the equipment or ensure smooth continuation of one turn. Similarly, such detection is also desired to detect phase loss in the output of an inverter, etc., and to protect it and protect the load.

Figure 8g4 shows a conventional instantaneous power failure/open phase detection circuit. When power is supplied from a three-phase power supply 1 to a device 2 such as an inverter, a detection circuit consisting of 3 to 6 is provided as one of the protection means for the device 2. The voltage detector 3 transforms the three-phase voltage of the three-phase power supply 1, the rectifier circuit 4 half-wave rectifies the three-phase voltage, and the comparator 5 converts this rectified waveform into the setting value V of the power outage voltage setting device 6,
This comparative output is used as an instantaneous power failure/open phase detection signal to obtain a protective action such as stopping the operation of the device 2.

With this configuration, as shown in FIG.
When the voltage drop in the voltage Vv of the phase voltage (U + vv + vw) during the period T1 exceeds the set value vI, the output of the comparator 5 is inverted, resulting in detection of an instantaneous power outage or an open phase during the period T1.

D1 Problems to be Solved by the Invention In the conventional detection circuit, for example, during the period T2 shown in FIG.
When an instantaneous power outage or phase loss occurs, the comparator 5 cannot detect the instantaneous power failure or phase loss due to the characteristics of the rectified waveform. This also applies to the other two phases, and there are more than half of the periods in which instantaneous power outages and phase loss cannot be detected for each phase.

Regarding this point, if the rectifier circuit 4 is a full-wave rectifier, the undetectable period will be reduced, but the undetectable period will still remain.

Means and Function for Solving the E1 Problem The present invention has been made in view of the above problems, and uses high gain amplification and absolute value conversion for each phase voltage detection output of a multiphase power supply. A waveform processing circuit, an OR gate that obtains an instantaneous power failure detection output by a logical sum output of the outputs of the respective waveform processing circuits, and a logical product of the outputs of the respective waveform processing circuits, and this logical product output continues for a certain period of time or more. The circuit is equipped with a circuit that sometimes obtains an open phase detection output, and by high gain amplification and absolute value conversion, a pulse waveform that becomes a zero point only near each Wakoto loss point is obtained, and the logical sum of this produces a momentary power outage that becomes a zero point for each phase. is detected, and open phase detection is performed when the zero point width of the pulse waveform exceeds a certain value.

F. Example FIG. 1 is a circuit diagram showing one embodiment of the present invention.

Three-phase detection voltage from the power supply to be detected vU + vV +
vw has waveform processing circuits 11U, 11-v, 1
．． It is made into an input signal of 1W. Waveform processing circuit 11U,
llv, 1], w, as represented by 1.1H, the input signal is amplified by the high gain amplifier 12U, this output is converted into an absolute value waveform by the absolute value circuit 13U, and this converted output is The waveform is shaped by cascaded logical inverters 14U and 15U with hysteresis.

Waveform processing circuit 11U, Ilv, 11. Each output U2 * "2 * W2 of w is input to the logical sum of the OR gate 16 and taken out as an instantaneous power failure detection signal to the output of the OR gate 16, and is input to the logical product of the Nant's gate 17. The output of the Nant gate 17 is taken out as an open phase detection signal in cooperation with the next stage timer.The output of the Nant gate 17 is input to the timer 18, and the timer 18 detects an open phase when the input continues for more than a set time. The output of the OR gate 16 and the output of the timer 18 are input to an AND gate 19, and the logical OR operation output of the AND gate 19 is used as the instantaneous power failure/phase loss detection output.

Waveforms of various parts in such a configuration are shown in FIG. By high gain amplification and absolute value conversion of the three-phase voltages U, vv, and vw, for example, the output of the amplifier 12U reaches a saturation value, and the output of the absolute value circuit 13U falls sharply only near the zero-crossing point of the phase voltage. It becomes a waveform. By shaping these waveforms, for example, the output of the logic inverter 15U becomes a pulse that becomes logic "0" only near the zero crossing point.The logic period T5 of this pulse is very short, and each phase-period is The ratio is negligible. When the OR gate 16 obtains the logical sum of these pulses, its output U+V+W will always be logic 11# if the power supply to be detected is normal, and at the time of a momentary power failure, each phase voltage will be zero and the output will be logic ``O'' only during that momentary power failure.
” and you can get the instantaneous power failure detection output.

On the other hand, the signal U2 which becomes a pulse output. The outputs U, ■, and W of the Nant gate 17 that obtain the logical product of v21w2 are not pulse train signals of period T5 if the power supply is normal, and for this pulse, the timer 18 is activated for pulses that continue for a period of 15 or more. By setting to obtain the output, if the period is 15 or more when the phase is open, it is possible to obtain the open phase detection output which becomes logic 10# as the timer output.

Here, since the period T5 is a very short period as described above, if the timer 18 detects a pulse having a period of 15 or more as an open phase, it is possible to detect an open phase with a high probability.

From these detection outputs, the AND gate 19 performs an OR operation for the instantaneous power failure detection output and the phase loss detection output, so that one of the detection outputs is logic "0" and an instantaneous power failure/phase loss detection output can be obtained.

In addition, in the event of a momentary power failure, the output of the timer 18 also becomes the 10# output, but the outputs of the OR gate 16 and timer 18 are individually drawn out to the husband, and instantaneous power failure and phase loss are detected individually, and the protection corresponding to the husband is provided. You can get the action.

In addition, in the embodiment, the waveform processing circuit 1iUHIlv
The high gain amplifier (for example, 12U) provided in 111W is not intended to operate as a comparator with infinite gain. The reason for this is that if a comparator is used as a temporary comparator, chattering will easily occur near the zero cross of the three-phase voltages vU, ■v, and vw, and when a hysteresis circuit is provided in the comparator to prevent this chattering, as shown in Figure 3. When a momentary power failure occurs, the hysteresis operation causes a malfunction in which the instantaneous power failure detection output cannot be obtained.

Further, in the embodiment, the voltage detection signal can be obtained by using a detection transformer for synchronizing the power supply with the phase control of the device such as an inverter.

In addition to the effects of the G1 invention, according to the present invention, instantaneous power outages and open phases are detected by logic processing after each phase voltage signal is subjected to high gain amplification and absolute value waveform processing. This has the effect of reliably and individually detecting instantaneous power outages and phase failures except during the pulse period, and the circuit configuration does not become complicated.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, FIG. 3 is a detection waveform diagram when a comparator is used instead of the amplifier in the embodiment, and FIG. The figure is a conventional detection circuit diagram, and FIG. 5 is a conventional detection waveform diagram. 11U, llv, Ilw... waveform processing circuit,
12U...High gain amplifier, 13U...Absolute value circuit,
14U, 15U...Logic inverter, 16...
OR gate, 17... Nante gate, 18... Timer, 19... AND gate. Figure 4 Conventional detection circuit diagram Figure 5 Conventional detection;

Claims (1)

[Claims] a waveform processing circuit for each phase that performs high gain amplification and absolute value conversion on each phase voltage detection output of the multiphase power supply; and an OR gate that obtains an instantaneous power failure detection output by a logical sum output of the outputs of the respective waveform processing circuits; Momentary power outage/phase loss of a multiphase power supply, characterized by comprising a circuit that takes the logical product of the outputs of the respective waveform processing circuits and obtains a phase loss detection output when the logical product output continues for a certain period of time or more. detection circuit.