JPS6097279A - Phase detecting method - Google Patents

Abstract

PURPOSE:To make it possible to achieve phase detecting work in an extremely safe and simple manner, by setting arbitrary one of buses as a reference bus while taking AC components from two remaining buses in a non-contact state and judging the timewise before and after relation thereof. CONSTITUTION:Freely openable and closable chip shaped electrode terminals T1, T2, T3 are attached to the insulating covers of three power source buses and AC components taken out from the power source buses at terminals T1, T2 in a non-contact state are amplified by an operation amplifier OP and a low frequency component is cut. A trapezoidal wave from the operation amplifier OP is differentiated by a differentiator circuit CR3 and inputted to reset set flip- flop. The pulse out of this RS-FF is inputted to an integrator circuit CR4 where only the rising part of the pulse is integrated and, because integration output becomes higher than a threshold level at the time of a positive phase, a light emitting diode LED emits light and generates no light at the time of an inverse phase.

Description

Detailed Description of the Invention This invention uses any one of the three power supply wires through which three-phase alternating current flows as a reference bus, and extracts AC components from the remaining two busses without contact. The present invention relates to a phase detection method that determines the temporal relationship in which an AC waveform progresses and detects positive phase and negative phase.

In a three-phase AC system that uses three wires to transmit AC power, there is a distance of 120 degrees between the currents flowing through each wire, as shown in Figure 1.
There is a phase difference of 12 degrees, and there is a phase difference of 12o6 between the voltages between the lines, although the magnitudes are the same. For convenience, the three busbars through which the three-phase alternating current flows are divided into R phase, S phase, and T phase, but when connecting a load such as a three-phase induction motor, the U phase, It is necessary to match each phase with the phase. If the connection is incorrect, the direction of rotation of the load may be reversed, or a malfunction may cause a breakdown of the power supply system.

Therefore, a phase detector is generally known as a measuring means for detecting and displaying the positive phase and negative phase in three-phase alternating current. However, with conventional phase detectors, the clip attached to the terminal of the detection probe is directly clamped and connected to the live wire's live part where three-phase alternating current is coming. It was extremely dangerous in the sense that it was applied to Furthermore, as mentioned above, in order to clip the probe to the live wire's live part, it is necessary to open the case of the electromagnetic switch, terminal block, and other control panels, and furthermore, the phase detection work itself is complicated in a confined space. Improvements are being requested as there are problems that are making it difficult for the government to operate.

The present invention has been proposed in order to satisfactorily solve the above-mentioned drawbacks, in view of the fact that when connecting a three-phase alternating current to a load, it is necessary to detect and distinguish between positive and negative phases to make a correct connection. This allows phase detection work in three-phase alternating current to be accomplished extremely safely and with simple operation.

In other words, the inventor found that in order to make the phase detection work safe, it is necessary to abolish the conventional method of directly connecting the probe to the live wire's live part and perform phase detection without contact. As a result of the conclusion and repeated prototype inspections based on this premise, it is possible to extract an AC component as a capacitance between the metal core wire and the insulation coating of each bus bar, depending on the strength of the electric field.
We came up with the idea that this relationship can be considered similar to that of a capacitor.

In addition, for phase detection in three-phase AC, it is sufficient to use any one of the three power supply buses as a reference and determine the positive phase and negative phase for the other two buses, as shown in Figure 2. If we take the T phase of the three AC waveforms as a reference on the time axis, the other two phases (R phase, T phase) will have the relationship of two stretched AC waveforms whose waveforms progress with a time difference, We also found that the positive and negative phases can be determined by determining this temporal precedence relationship.

Therefore, in the phase detection method according to the present invention, any one of the three power supply buses through which three-phase alternating current flows is taken as a reference, and AC components are extracted from the remaining two buses without contact, and low frequency components are removed. Then, by differentiating each AC component, two falling pulse waveforms with a time difference are obtained, and these two falling pulses are input to a flip-flop as setting and reset conditions, and the flip-flop is reset immediately after being set. By doing this, it becomes high for a short time (h
After setting the pulse that becomes high) or setting it, there is a slight margin of time until the flame is reset.
The present invention is characterized in that it outputs any one of the pulses that maintains the ) shape 21M and integrates the obtained pulse to drive a display means that displays either the positive phase or the negative phase.

Next, the phase detection method according to the present invention will be described in detail using preferred embodiments. FIG. 3 shows an example of a circuit used to implement the method of the present invention, and FIG. 4 shows the state of signals at points (A) to (D) in the circuit. Shown as a time chart. Each terminal T, , T2. T is configured as a lip-shaped electrode terminal that can be opened and closed, and can be detachably attached to the insulation coating of three power supply buses through which three-phase alternating current flows.

Of the three electrode terminals, the 'R terminal is connected to a reference bus arbitrarily selected from the three power supply buses in a non-contact manner.

In order to match the waveform diagram shown in FIG. 2, this reference bus line is assumed to be in T phase.

The other two terminals T and - are respectively connected to the remaining power supply bus in a non-contact manner, but it is of course unclear at this point whether this bus is in the R phase or the S phase.

The two terminals - and T2 are connected as inputs to circuits A and B, respectively, which have exactly the same configuration.

This circuit A (B) includes, for example, a CMOS digital TC,
It basically consists of a differential circuit, and the terminals "r, (
72) is amplified and waveform shaped. That is, the AC component extracted from the power supply bus at the terminal hair without contact is amplified by the operational amplifier OP, but at this time, the appropriate amplification factor is set by the resistor P inserted in the operational amplifier OP (the amplification factor is If it is too sensitive, external noise will be easily picked up, and if the amplification factor is too low, the extracted AC component cannot be effectively signal-processed).

Furthermore, by using the resistor inserted in the operational amplifier OP, for example, low frequency components of 60 Hz or less among the AC components are cut. Therefore, in (A)A of circuit A, there is a trapezoidal wave T in which the excessive amplification is sliced, as shown in Fig. 4 (A).
, appears, and a trapezoidal wave T also appears at point (A) of circuit B.
7 appears. However, the side trapezoidal wave -1- has a time difference Td because the alternating currents that form the basis of the waveform progress with respect to each other in time.

The trapezoidal waves T and - shown in FIG. 4(A) described above are differentiated in differentiating circuits consisting of capacitors C and resistors P3 in circuits A and B, respectively, and fall as shown in FIG. 4(B). A pulse that falls singly with a time lag before being shaped into a pulse waveform is input as a reset signal and a set signal to a reset set flip-flop (R3-FF) provided at a subsequent stage. In other words, (B
Since one falling pulse T, shown in ) is temporally earlier than the other falling pulse -, if the falling pulse T, enters the flip-flop (R3-FF) first, the falling pulse T, shown in FIG. The flip-flop is set (S), but the time difference T
Immediately after d, a subsequent falling pulse arrives to reset (R) the flip-flop. Therefore, at point (C) in the circuit shown in Fig. 3, as shown in Fig. 4 Q,
An asymmetric pulse waveform with a short high time is obtained. Moreover, the flip-flop (R3-
When the falling pulse (FF) enters first, the flip-flop is set (s) and after some time, the flip-flop is reset (R).
As shown in FIG. 2, an asymmetric pulse waveform having a relatively long high time is obtained.

After selectively obtaining the pulse waveform of either Q or Q2 shown in FIG. 4 in this way, this pulse waveform is input to an integrating circuit formed by resistors P4 and C,
By integrating only the rising edge and not integrating the falling edge of the pulse, a waveform as shown in FIG. 4 is obtained at point (D). This waveform signal drives an appropriate display means to display the positive phase and negative phase. For example, in this embodiment, the waveform is amplified by the operational amplifier OP in the subsequent stage, but Q? In the case of a waveform as shown in , since it is above the threshold level, the light emitting diode L ED emits light to let the inspector know that it is in the correct phase. However, in the case of a waveform as shown in Q in FIG. 4, the light emitting diode LED does not emit light because it is below the threshold level, indicating that the phase is reversed. Various types of display means are possible, such as using a sound generating means such as an electronic buzzer to make the inspector aware of the warning sound, or distinguishing the warning sound into continuous sound and intermittent sound. It has been proposed to use a combination of a luminescent display and an acoustic display.

As explained in detail above, according to the phase detection method according to the present invention, any one of the three power supply buses is used as a reference bus,
The AC component is taken out from the other two power buses without contact to obtain two pulse waveforms with a time difference, and due to the temporal precedence relationship between these two pulse waveforms, the pulse remains high for a long time. It obtains a waveform or short pulse waveform and uses it to drive a display means such as a light emitting means or an acoustic means to tell the state of normal phase and reverse phase. On the other hand, it is extremely safe because phase detection can be performed without contact. In addition, the simple operation of attaching the probe terminals to the insulation coating of each power bus bar with clips is sufficient, so there is no need to open the terminal board or switch case, and it can be used anywhere. has.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram of three-phase AC, and Figure 2 is one of the three-phase AC.
An explanatory diagram of AC waveforms flowing through two other power supply buses when one power supply bus is taken as a reference and this is taken as a time axis,
FIG. 3 is a wiring diagram of an example of a circuit used to implement the phase detection method according to the present invention, and FIG. 4 is a diagram (A) of the circuit shown in FIG.
It is a timing chart figure which shows the state of the signal at each point of - (D).

Claims (1)

[Claims] Using any one of the three power supply buses through which three-phase alternating current flows as a reference, extracting AC components from each of the remaining two buses without contact, removing low frequency components, and differentiating each AC component. obtain two falling pulse waveforms with a time difference, input these two falling pulses to a flip-flop as a set and reset condition, and reset the flip-flop immediately after switching to a high level for a short period of time. Output either a pulse that becomes high (high) or a pulse that maintains a high state for a long time with some time margin until the fire is reset after being sent to cellar 1, and integrate the obtained pulse. A phase detection method characterized by driving a display means that displays either a positive phase or a negative phase.