JPH01136519A - Electronic type circuit breaker - Google Patents

Abstract

PURPOSE:To detect an overcurrent with a simple configuration having two current detectors by employing first and second power source detectors for detecting the sum or difference of currents flowing to leads. CONSTITUTION:The sum or difference of currents flowing to two 3r, 3s of 3-wired leads 3r, 3s, 3t is detected by a current detector 6, and the sum or difference of the currents flowing to the two leads 3s, 3t is detected by a current detector 9. The outputs of the detectors 6, 9 are input through rectifiers 12, 14 to a controller 25, and the currents flowing to the leads 3r, 3s, 3t are calculated. When the calculated current value exceeds a predetermined value, a thyristor 23 is conducted, and a breaking switch 20.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic circuit breaker. The present invention relates to an electronic circuit breaker that interrupts an electric circuit including the conductive wire when the conductive wire is exceeded.

[Conventional technology] Accurately prevents overcurrent from flowing in the conductive wires when a device with large power consumption is connected to the conductive wires of a 3-wire system (R phase, S phase, T phase) or when a ground fault occurs. In order to prevent this problem with good response, electronic circuit breakers have conventionally been used. In this type of circuit breaker, a conductive wire is passed inside a toroidal current transformer (hereinafter also referred to as CT), and each
There is a device configured to cut off all the conductive wires when the current value flowing through each conductive wire detected by the above exceeds a preset upper limit value. A toroidal current transformer generates an induced electromotive force by changing the current flowing through the conductive wire inside the toroid, and can detect the magnitude of the current flowing through the conductive wire with extremely high accuracy. Therefore, by amplifying the output of this CT and driving an electromagnetic or semiconductor switch as a cut-off means, the conductive line can be cut off with high accuracy and responsiveness.

[Problems to be Solved by the Invention However, improvements in the margins were desired in the following points. CT and CT fittings and electrical components must be provided independently for each conductive line. Therefore, in the case of a three-wire system, three CTs, their electrical parts, and mounting parts are required.

Since the size and weight of these elements account for a large portion of the electronic circuit breaker, there is a problem in that there is a limit to miniaturization, and the number of parts increases, which requires manufacturing man-hours.

The electronic circuit breaker of the present invention has been made for the purpose of solving the above problems and suitably preventing overcurrent.

The structure of the present invention that achieves the above object will be described below.

[Means for Solving the Problems] The electronic circuit breaker of the present invention interrupts an electric circuit including the conductive wire when the current flowing through at least one of the three-wire conductive wires exceeds a predetermined value. An electronic circuit breaker is equipped with a circuit breaker that detects the sum or difference of currents flowing through two of the three-wire conductive wires; a second current detector for detecting the sum or difference of currents flowing through two conductive wires in a combination different from that of the first current detection means;
calculation means for calculating the current value flowing through the three-wire conductive wire by calculating the output of the current detector; and driving means for driving the cutoff means when the calculated current value exceeds a predetermined value. Here, the current flowing through the three-wire conductive wire may be either three-phase or single-phase alternating current. 1st and 2nd
The current detector detects the sum or difference of currents flowing through two of the three-wire conductive wires. Examples include a toroidal current transformer that detects current from the induced electromotive force generated by changes in the current flowing through two conductive wires, and a configuration that inserts a low resistor in each conductive wire and detects the voltage across the low resistor. be able to. When a current transformer is used, the sum and difference of currents can be easily detected by inserting two conductive wires into the current transformer in the same or opposite directions.

The calculation means calculates the value of the current flowing through the three-wire conductive wire by calculating the outputs of the first and second current detectors. For example, as shown in Figure 1, three-phase intersection? m (R phase, S phase, T phase), the sum of currents IR and IS flowing in the R phase and S phase is detected by the first current detector, and the S phase,
If the configuration is such that the sum of currents IS and IT flowing in the T phase is detected by a second current detector, and the outputs of the first current detector and the second current detector are combined, each output is Currents it, ir flowing through resistors Rt, Rr, Rs
, is, the following equations are obtained from the relationship: IR+Is+IT:O-(1). That is, it
= (IR+l5)=IT...-(2)ir=
(Is+IT)=IR-(3)is=it+ir
=-Is... (4) Therefore, the current it, i
By detecting the values of r and is, it is possible to know the current flowing in each phase. Alternatively, the calculation may be performed by rectifying the currents it, ir, and is. Furthermore, a function may be added to detect a ground fault by assuming that the relational expression (1) no longer holds true when a ground fault occurs.

In addition, in the case of a configuration in which the first current detector detects the difference between the currents flowing in the R phase and the S phase, and the second current detector detects the difference in the currents flowing in the S phase and the T phase, the resistance Equipment Rt, Rr, R
The current it, ir flowing through s.

is is as follows.

it= (IRIS) −(5)ir=
(IT Is) −(6)is=i
t+i r=3◆ IS Furthermore, equation (5), (
6), it is possible to obtain 1t-2◆1r=3◆■T i r-2+ it=3+ IR. Therefore, even when the first and second current detectors detect the difference between two of the three-wire conductive wires, the currents of each phase can be detected.

The interrupting means may be configured to interrupt all of the 3-wire conductive wires within the electronic circuit breaker, or may be provided outside the electronic circuit breaker and connect the 3-wire conductive wires within the electronic circuit breaker to one part of the circuit. Examples include a configuration that interrupts the electrical circuit connected to the unit. The interrupting means can be realized by a semiconductor switch such as a triac or an electromagnetic relay.

[Operation] The electronic circuit breaker of the present invention having the above configuration detects the sum or difference of the currents flowing through two of the three-wire conductive wires using the first current detector, and The second current detector is used to detect the sum or difference of the currents flowing through two of the three-wire conductive wires in a different combination from the first current detector, and the calculation means The current value flowing through the three-wire conductive wire is calculated from the output of the current detector No. 2, and when the calculated current value exceeds a predetermined value, the cutting means is driven by the driving means, including the three-wire conductive wire. Break the electrical circuit.

[Examples] In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the electronic circuit breaker of the present invention will be described below. FIG. 2 shows the configuration of the electronic circuit breaker of the embodiment.

As shown in the figure, the electronic circuit breaker 1 of this embodiment includes a toroidal current transformer (CT) 6 through which conducting wires 3r and 3s of the R phase and S phase of the three-phase alternating current are inserted.
and S-phase and T-phase conductive wires 3s.

A toroidal current transformer 9 that inserts a CT 3t inside, a rectifier 12, 14 that performs full-wave rectification of the outputs of the two CTs 6 and 9, and R-phase, S-phase,
An electromagnetic cutoff switch 20 cuts off all conductive wires 3r, 3s, and 3t of the T phase, and a trigger pulse is output to the thyristor 23 to pull the cutoff switch 20 when the output of the rectifier 12.14 exceeds a predetermined value. The control circuit 25 is configured to include a control circuit 25 that drives the removal coil 20a.

In order to clearly explain the function of the electronic circuit breaker 1 configured in this way, one C
This will be explained in comparison with the functions of a conventional electronic circuit breaker equipped with a T. FIG. 1 and FIG. 3 are circuit diagrams schematically showing current detection in the electronic circuit breaker of this embodiment and current detection in a conventional electronic circuit breaker, respectively.

FIG. 4 is a circuit diagram schematically representing a current detection section of a conventional electronic circuit breaker.

First, the case of three-phase equilibrium will be explained. In other words, 1
Equal amplitude voltages with 20 degree phase difference (R phase, S phase,
T phase) is applied between each conductive wire, and loads with equal resistance values are connected between each conductive wire (switches S1.S2.S3 in FIG. 1 and switches S4.S5. in FIG. 3). S
6 are all closed). At this time, the output currents IR, Is, and IT from each CT (see Figure 3) provided for each conventional conductive line have a phase difference of 120 degrees as shown in the vector of the dotted chain line in Figure 5. The amplitudes will be equal. On the other hand, the output type from the CT (see Fig. 1) of this embodiment? iit, ir and their combined current is,
From the formula % formula % (2) mentioned above, as shown by the solid line vector in Figure 5, between 1r and is,
The phases between 1s and ir have the same amplitude and are shifted by 60 degrees. Figures 6(A) and 6(B) show the actually measured current waveforms. Current waveform IRI IS,
IT, ir, is, and it are sinusoidal waveforms with different phase differences, but as shown in Figure 7, the rectified voltage ■
, ■ (■ is the voltage across resistor R in Figure 4, ■ is the voltage across resistor R in Figure 2
Represents the voltage at a point. ) have almost the same output waveform.

Next, a case in which three phases are unbalanced will be explained. In other words, when the R-phase to 8-phase conductive wires are open and loads with equal resistance values are connected between the S-phase to T-phase and R-phase to T-phase conductive wires (switches S1 and 3 in Figure 1 Only switch S4 in the figure is off). At this time, the output current IR of the conventional CT
, Is, IT, the amplitude of the output current IT is equal to the output current IS, I when the phase difference between IRIs is 60 degrees and the phase difference between I5IT is 150 degrees, as shown in the vector of the dotted chain line in Fig. 8.
The amplitude is twice that of R. On the other hand, the CT of this example
The output current of 6°9 has a phase difference of 120 degrees between 1r and is and a phase difference of 30 degrees between 1s and it, as shown by the solid line vector in Figure 8, and the amplitude of the output current 1t is output type? mts, ir
The amplitude will be twice that of . Figures 9(A) and 9(B) show these actually measured output waveforms. As shown, the output waveform of the conventional CT and the output waveform of this embodiment are different, but in FIG. 10(A).

As shown in (B), if the absolute values are taken, the waveforms are almost the same. Therefore, as shown in FIG. 11, the rectified output voltages (1) and (2) almost match.

Next, open the conductive wires of the S phase and T phase, and open the conductive wires of the R phase and
When a load of equal resistance value is connected between the 5-phase, R-phase and T-phase conductive wires (only switch S2 in Figure 1 and switch S5 in Figure 3 are off), ζ trouble occurs when three phases are unbalanced. explain. Vector of output current in Fig. 12, Fig. 13 (A)
, As shown in the current waveform in (B) and the rectified voltage waveform in FIG. 14, the current waveforms are different, but the output waveforms (2) and (2) after rectification are almost the same, as in the case of three-phase unbalance.

Furthermore, the conductive wires of the R phase and T phase are opened, and the conductive wires of the S phase and R phase are opened.
Even in the case of three-phase unbalance when a load of equal resistance value is connected between the S-phase and T-phase conductive wires (only switch S3 in Fig. 1 and switch S3 in Fig. 3 are off), the 1
As shown in the output current vector in Figure 5, the measured current waveforms in Figures 16 (A) and (B), and the rectified voltage waveform in Figure 17, the current waveforms are different, but the output waveform after rectification is ■
are almost the same.

As explained in detail above, the electronic circuit breaker 1 of this embodiment
Inserting the conductive wires 3r and 3s inside -11 = The sum of the outputs of the CT6 and the output of the CT9 passing the conductive wires 3s and 3t inside are rectified by rectifiers 12 and 14, respectively, depending on the load condition. C to all conductive wires regardless of
This corresponds to the output of a conventional electronic circuit breaker equipped with T. Therefore, when the sum of outputs after rectification exceeds a preset value, for example 60 [A], the electronic circuit breaker 1
5 outputs a trigger pulse to the thyristor 23, turns on the thyristor 23, drives the tripping coil 20a, and connects all the conductive wires 3r and 3s of the R phase, S phase, and T phase.

3t contact 20b is turned off to shut off.

As shown above, the electronic circuit breaker 1 of this embodiment has only two CT6.9s, and is a three-wire type circuit breaker similar to the conventional electronic circuit breaker using three CTs. Conductive wires 3r, 3
It is possible to prevent overcurrent of the current flowing through s and 3t. Therefore, it is possible to omit the set of CTs, their attachment parts, and electrical parts, and to reduce their size and weight.

In addition, the number of parts can be reduced to reduce costs and manufacturing man-hours.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way. For example, the present invention may be applied to a single-phase three-wire conductive wire instead of a three-phase three-wire conductive wire. Good too. Figure 18(A).

(B) and (C) are R phase-8 in Fig. 2, respectively.
CT6 when single-phase voltage is used between phases, between R phase and T phase, and between S and T phases. Observe the output voltage of CT9 and the output voltage after rectification. As shown in the figure, the voltage waveform after rectification is the same in either case.

Note that the hotline may be IP or 2P.

As detailed above, according to the electronic circuit breaker of the present invention, only the first and second current detectors are used, compared to the conventional case using three current detectors. Similarly, overcurrent of the current flowing through the three-wire conductive wire can be prevented. Therefore, it is possible to omit the second set of current detectors, their mounting parts, and electrical parts, and the size and weight of the current detectors can be reduced, resulting in miniaturization.

In addition, the number of parts can be reduced to reduce costs and manufacturing man-hours.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining current detection in the electronic circuit breaker of the embodiment, FIG. 2 is a circuit diagram showing the configuration of the electronic circuit breaker of the embodiment, and FIG. An explanatory diagram for explaining current detection, Fig. 4 is an explanatory diagram for the current detection section of a conventional electronic circuit breaker, Fig. 5 is an explanatory diagram for representing the output current as a vector, and Figs. 6 (A), (B) ) are graphs representing the output currents actually measured in the electronic circuit breaker of the example and the conventional electronic circuit breaker, respectively, FIG. 7 is a graph representing the output voltage after rectification, and FIG. 8 is an explanation representing the output current as a vector. Figures 9 (A) and (B) are graphs showing the output currents actually measured in the electronic circuit breaker of the example and the conventional electronic circuit breaker, respectively, and Figures 10 (A) and (B)
are explanatory diagrams representing the absolute values of the output currents of the electronic circuit breaker of the example and the conventional electronic circuit breaker, respectively, FIG. 11 is a graph representing the output voltage after rectification, and FIG. 12 is a vector representing the output current. Explanatory drawings, FIGS. 13(A) and 13(B) are graphs representing the output currents actually measured in the electronic circuit breaker of the example and the conventional electronic circuit breaker, respectively, and FIG. 14 is a graph representing the output voltage after rectification. , FIG. 15 is an explanatory diagram showing the output current as a vector, and FIGS. Figure 17 is an explanatory diagram showing the output voltage after rectification, Figure 18 (A), (B),
(C) shows the output current in each modified electronic circuit breaker. It is a graph showing the output voltage after rectification. 1... Electronic circuit breaker 6.9... Current transformer (CT)
12.14... Rectifier 20... Cutoff switch 20a... Tripping coil 23... Thyristor 25... Control circuit

Claims (1)

[Scope of Claims] An electronic circuit breaker comprising interrupting means for interrupting an electric circuit including the conductive wire when a current flowing through at least one of the conductive wires of a three-wire system exceeds a predetermined value. , a first current detector that detects the sum or difference of currents flowing through two of the three-wire conductive wires; and a first current detection means among the three-wire conductive wires. a second current detector that detects the sum or difference of currents flowing through two conductive wires of different combinations;
calculation means for calculating the current value flowing through the three-wire conductive wire by calculating the output of the current detector; and driving means for driving the cutoff means when the calculated current value exceeds a predetermined value. An electronic circuit breaker characterized by being equipped with.