JPS60174958A - Phase decision apparatus - Google Patents

Abstract

PURPOSE:To enable accurate decision on the phase whether it is single or three phase by judging the phase based on a line voltage signal and a phase current signal. CONSTITUTION:Line voltages P12 and P32 are converted into line voltage signals V12 and V32 of a square waveform with comparators 1 and 2 and fed to single/three phase discriminator section 10, which sends a discrimination signal G of H level to a switching section 20b when judging it as single phase while that of L level, as three phase. When single phase is found, the switching section 20b sends a signal V12 to an input terminal D of an FF30 while when three phase is found, it sends a line voltage signal Vs delayed in the phase by 90 deg. with a delay section 20a to a terminal D of the FF30. Depending on the lag or advance of the phase between the voltages V12 and Vs and the phase current signal I obtained by the conversion of a phase current I1, an H-level signal is outputted from an input terminal Q of the FF30 when the phase is in lag while an L-level signal is outputted when it is in advance. Thus, whether the power source is single or three phase, it can be automatically judged by lag or advance in the phase. As the phase current I1 is amplified to a specified level with an amplifying section 40, the magnitude of the phase current I1 will not affect the decision on the phase however it may be limited.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a device for measuring the power factor of a load to which electric power is supplied, and in particular to a phase determination device for determining whether the power factor is due to a lagging phase or a leading phase. O Regarding the device [Technical background of the invention and its problems] Improving the power factor of the load to which electric power is supplied is one of the important items in the review and improvement measures of the load, that is, the electrical equipment, and in reality there is no progress. Power factor improvement is performed using phase capacitors. By the way, conventional power factor measuring devices used in electrical equipment mainly measure power at the receiving end of a three-phase, three-wire power source, whereas current power factor measuring devices measure in low-voltage systems. The need for power factor correction necessitates a dual-use device that measures the power factor for both single-phase and three-phase three-wire power supplies. When determining whether the power factor is a lagging power factor or a leading power factor, a common method is to use the difference in phase angle between the voltage and the load current to determine whether the power factor is lagging or leading. However, the phase of the voltage (line voltage) and load current is different between single-phase and three-phase three-wire power supplies, so in conventional equipment, phase determination circuits are used for single-phase and three-phase three-wire systems, respectively. In addition, the operator operated an external switching means depending on the single-phase and three-phase three-wire systems. For this reason, the configuration of the device becomes complicated and handling becomes inconvenient. Furthermore, the current value of the load current used for phase determination may become small due to variations in the load, which may cause errors in phase determination.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and is capable of automatically and accurately determining phase lead or lag regardless of whether the power source is single-phase or three-phase, and even if the load current is small. The purpose is to provide a complete evaluation device.

[Summary of the invention]

The present invention provides a signal switching section that responds to a discrimination signal sent from a single-phase three-phase discrimination section that discriminates between a single-phase power supply and a three-phase power supply, and in the case of a single-phase power supply, a line voltage signal of the single-phase voltage. is sent out without changing its phase, and in the case of a three-phase power supply, the line voltage signal of a predetermined line voltage of the three phases is sent out with the phase shifted by a predetermined phase angle, and the This is a phase determination device in which a determination unit determines whether the phase is slow or advanced based on a voltage signal and a phase current signal of a predetermined phase current.

[Embodiments of the invention]

An embodiment of the phase determination device according to the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a configuration diagram of the Fi phase determination device. In Figure 1, ■(PI3
) is the line voltage between the first phase and the second phase, V(P3□)Fi is the line voltage between the third phase and the second phase, and these line voltages ■
(PI3) +v(P32) is due to the transformer section and AC section in the power factor measuring device! l) It is attenuated to a voltage level that allows operation. The line voltage V (PI3) is converted by the comparator 1 into a first line voltage signal V12 having a rectangular waveform, and then sent to the single-phase and three-phase discriminator 10. The line voltage V (Psz) is sent to comparator 2.
The signal is converted into a second line voltage signal V32 having a rectangular waveform and sent to the multi-phase three-phase determining section JO, and then to the phase advance section 21 of the signal switching section 20.

The single-phase and three-phase discriminator 10 detects the line voltage signal V1! and V3
2 determines whether the power supply is single-phase or three-phase, and if it is single-phase, it is “H”.
” level, and if it is three-phase, it has the function of sending out a discrimination signal G of “L” level, and the discrimination is based on the line voltage signal V1.
2 # This is done based on the difference in phase angle between VS2. In other words, single-phase and three-phase line voltage V (PI3) * V (
pH2) and the phase current V(I*) of the first phase are represented by vectors. In a single-phase two-wire system, the line voltage vector ψ12 between the first and second phases is shown in Figure 2(a). and the first phase current vector il are in phase. In addition, the third phase and the second phase
The line voltage vector 32 between the phases is the line voltage v of the device.
The input terminal of (Psz) is connected to the input terminal of line voltage V (Pfi). In addition, in a single-phase three-wire system, the second
As shown in figure (b), the line voltage vector 12 and 32
If the phase angle between the
As shown in c), the phase angle between the line voltage vectors *12 and *32 is 60 degrees. Note that i3 is the phase current vector of the third phase.

Note that the power factor in FIGS. 2(a), (b), and (c) is 1.
This is the case of 0. Therefore, the single-phase determining unit 10 determines whether the voltage is single-phase or three-phase based on the phase difference between the line voltages v (PI3) and v (psz).

If the discrimination signal G sent from the single-phase three-phase discrimination section 1o is at rHJ level, the signal switching unit 20 sends out the line voltage signal V12, and if the discrimination signal is at rLJ level, it sends out the line voltage signal V12 delayed by 90 degrees. (Po) as the third line voltage signal 8, and is composed of a delay section 20h and a switching section 2ob. Specifically, the delay section 20a
is a phase advance part 2 which advances the phase of the line voltage v (P32) by 90 degrees, a comparator 22 which converts the voltage output from this phase advance part 21 into a square waveform, and this comparator 22.
It is composed of an inverter 23 that inverts the line voltage signal V32 sent from the line voltage signal V32. The switching unit 20b inputs the discrimination signal as a dirt signal to one end, and inputs the line voltage signal V to the other end.
And dart 24 to input tZ, inverter 2 at one end
5, the discrimination signal G is inputted as a dart signal, and the line voltage signal V sent from the inverter 23 is inputted to the other end of the AND gate 26, and the line voltage signal V passing through the AND gate 24. The signal is sent through V to the data input terminal of a D-type Fritzno flop 30 serving as a determining section. It consists of 27 ordarts.

On the other hand, the first phase current V (Is) is configured to be input to the clock input terminal CK of the flip 70 fso via the amplifier section 40 and the converter 50. Note that the amplifying section 40 includes an operational amplifier 41 and resistors 42 and 43.

Next, the operation of the apparatus configured as described above will be explained. The line voltages v (PI3) and V (P32) are converted from AC waveforms into line voltage signals "12 + VS2" with square waveforms by comparators 1 and 2, respectively, and sent to the single-phase and three-phase discriminator 10. The phase/three-phase discrimination unit 10 discriminates whether the input line voltage signal V121V32 is a single phase or three phase based on the phase angle between them. If it is determined that it is the phase, a determination signal G of rLJ level is sent out.

Therefore, in the case of a single-phase power supply, the rHJ level discrimination signal G opens the υ AND gate 24, and the line voltage signal V12 passes through the AND gate 24 and the OR gate 27 to the data input terminal of the 7-rip 70-f30. sent to. In addition,
At this time, the AND dirt 26 is operated by the inverter 25)
Since the rHJ level discrimination signal G is inverted, it is closed.

Further, in the case of a three-phase power supply, the discrimination signal G at the "L" level is inverted by the inverter 25 and input to the AND gate 26, so that the AND gate 26 is opened. Therefore, the phase of the line voltage V (, P32) is advanced by 90 degrees by the phase advance unit 21, and converted into a rectangular waveform by the comparator 22.
Furthermore, the line voltage signal V is inverted by the inverter 22.
(line voltage signal VS whose phase is delayed by 90 degrees with respect to the phase of the line voltage V (P32))
and is sent through the OR gate 27 to the data input terminal of the flip-flop 30.

On the other hand, the phase current V (Il) is non-invertingly amplified to a predetermined level by the amplifier 40, and further converted by the comparator 50 into a phase current signal It having a rectangular waveform. sent to.

Thus, the line voltage signals V12 and Vs and the phase current signals 1, . The relationship between the two is shown in FIGS. 3(a) and 3(b). In addition, Figure 3 (
a) (b) shows the case where the power factor is 1.0. In other words, in the case of a single-phase power supply, as shown in Figure 13 (, ), the line voltage vector 12 and the phase current vector 〒1 are in phase,
Similarly, in the case of a three-phase three-wire system, the line voltage vector ÷8 and the phase current vector il are in phase, as shown in FIG. 3(b). In a three-phase three-wire system, if the phase of the line voltage vector *32 shown in FIG. 2(e) is delayed by 90 degrees, it becomes in phase with the phase current vector 11.

As a result, if the power factor is lagging, Frizzo Floss is 7°30
The phase relationship between the line voltage signal v12 #V and the phase current signal circuit 1 input to the data input terminal and clock input terminal CK, respectively, is as shown in Fig. 4(a). Voltage signal V1. ．． Since there is no delay with respect to V, the Q output terminal of the flip-flop 30 outputs "
January level signals are output.

On the other hand, the leading power factor! If so, the line voltage signal V12sVSZ
The phase relationship between the phase current signal and the phase current signal is as shown in FIG. A signal at the U rLJ level is output from the output terminal.

In this way, in this device, the switching unit 20b switches the line voltage signal V12 output from the comparator l in the case of a single phase to the 7-rip switch according to the discrimination signal G sent from the single-phase three-phase discrimination unit 10. The line voltage signal ■8 obtained by sending the signal to the D input terminal of F30 and delaying the phase by 990 degrees by the delay unit 20a in the case of three phases is sent to the data input terminal of F30, and these lines Phase current signal engineering obtained by converting the voltages vtz, v, and phase currents V(If)! Depending on whether the phase is delayed or advanced, the signal from the output terminal Q of the Frizzoflo f30 is rHJ level signal in the case of a delay, r in the case of a lead.
Since it outputs an LJ level signal, it can be used regardless of whether the power supply is single phase or three phase, i.e. single phase two wire, single phase three wire,
Regardless of the three-phase three-wire system, it is possible to automatically determine whether the phase is slow or fast. In this determination, the line voltage signal V that the signal switching unit 20 sends to the flip-flop 30 is
Since it is only necessary to switch tz+vs, determination can be made under the same conditions regardless of single phase or three phase. Therefore, this device does not require separate phase determination circuits for single-phase and three-phase use as in the past, and the operator does not have to operate external devices, resulting in a simple configuration. There is.

Further, since the phase current V(Is) is amplified to a predetermined level by the amplifier 4θ, even if the phase current V(11) is small, it does not affect the phase determination. Furthermore, the amplifying section 40
and comparator 5o, the error in the rise and fall times when converting the alternating current waveform of the phase current V (It) into a rectangular waveform is made extremely small. It is possible to stably determine whether the phase is slow or fast.

〔Effect of the invention〕

According to the present invention, the phase of the line voltage signal is shifted from the signal switching unit in accordance with the judgment signal sent from the single-phase three-phase judgment unit, and the line voltage signal is also sent out without phase shifting. Based on the phase difference with the current signal, the determination unit determines whether the phase is delayed or advanced, so whether the power supply is single-phase or three-phase, and the load current is small, it can be automatically and It is possible to provide a phase determination device that can accurately determine phase lead or lag.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a phase determination device according to the present invention, and FIGS. 2(a), 2(b), and (a) are vector diagrams showing the relationship between line voltage and phase current. Figures (,) are vector diagrams for single-phase two-wire systems, Figure 2 (b) are vector diagrams for Fi single-phase three-wire systems, Figure 2 (c) is vector diagrams for three-phase three-wire systems, and Figure 3 ( a) (b) are vector diagrams showing an example of a signal input to the flip 70 shown in Fig. 1, and Fig. 4 (a) (b)
) is a diagram for explaining the operation of determination by the 7-rig flop shown in FIG. 1.2...Comparator, 10...Single-phase three-phase determination section, 2o...Signal switching section, 20&...Delay section, 2ob
...Switching section, 2 No. Phase advance section, 22... Comparator, 23... Inverter, 24.26... AND gate, 25... Inverter, 27... OR gate, 4o... ... Amplification section, 41... Operational amplifier, 5o...
・Comparator, 30...D type frizzo flop. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 (C) (a) □v12 1 No. (a) Q Knee 1 --1 Figure 3 (b) Vs 1 Figure 4 (b) 1 -- Beeeeeeeeeeeeeoooooooooooooooo

Claims (1)

[Claims] A single-phase three-phase discrimination section that discriminates whether a stain source is single-phase or three-phase based on the phase difference between at least two line-to-line voltage signals obtained by converting the line voltage, and a signal sent from this single-phase three-phase discrimination section. If the power supply is single-phase, a predetermined line voltage signal among the line voltage signals is sent out, and if the power supply is three-phase, the predetermined line voltage signal is sent out among the line voltage signals. A signal switching unit that shifts a predetermined line voltage signal by a predetermined phase angle and sends out a predetermined line voltage signal different from the signal of and a determination unit that determines whether the phase is delayed or advanced based on the obtained phase current signal.