JPH03218219A - Three-phase three-wire circuit breaker with open phase protection function - Google Patents

Abstract

PURPOSE:To improve the reliability by comparing output voltage from an average circuit with voltage obtained by dividing output voltage from a peak value detection circuit and, if open phase is detected from the difference in voltage waveform between the terminals of three phases, opening a circuit. CONSTITUTION:In the case of phase interruption of a motor, the form of the full wave of voltage is transmitted from a rectification circuit 3, equalized in an averaging circuit 6, and entered to a comparison circuit 8. The form of the full wave is also transmitted to a peak value detection circuit 7, which detects a peak value detection waveform and transmits it to the comparison circuit 8 after voltage division. The comparison circuit 8 compares the average waveform with threshold voltage as the reference value obtained by voltage division and, if the value of the average waveform is under the reference value, transmits the signal thereof to a thyristor 10. The thyristor 10 allows a current to pass through a trip coil 11 according to the signal to operate the trip coil 11 and open a circuit.

Description

Detailed Description of the Invention A. Field of Industrial Application The present invention provides a three-phase three-wire open-phase protection function that detects differences in voltage waveforms between terminals of three phases, detects open phase, and opens the electrical circuit. Regarding circuit breakers.

Conventional technology A conventional 3-phase 3-wire circuit breaker with an open phase protection function detects an open phase from the current waveform obtained from a CT (current transformer) and operates a release electromagnetic tripping device. there were.

C. Problems to be Solved by the Invention The above-mentioned conventional three-phase three-wire type circuit breaker with open-phase protection function uses a release electromagnet, so it lacks vibration resistance, is prone to failures, and is easily affected by temperature. It has drawbacks such as requiring advanced manufacturing technology and being expensive.

Furthermore, since open phase detection is performed using CT, not only is the cost high, but three-phase three-wire open phase protection can only be applied to limited models.

2. Means for Solving the Problems In view of the problems of the conventional three-phase three-wire circuit breaker with an open-phase protection function, the present invention provides a three-phase three-wire circuit breaker that is highly reliable, easy to manufacture, and inexpensive. The present invention provides a circuit breaker with an open-phase protection function, and its configuration is such that, in an earth leakage breaker equipped with an open-phase detection mechanism, the open-phase detection mechanism includes a power supply circuit and a detection circuit, and the power supply circuit includes a rectifier circuit. and a constant voltage circuit, the detection circuit includes a rectifier circuit, an average value circuit that averages the signal waveform from the rectifier circuit, a peak value detection circuit that detects the peak value of the signal waveform, and the average value circuit that averages the signal waveform from the rectifier circuit. A comparison circuit that compares and judges the output voltage from the value circuit and the divided voltage obtained by dividing the output voltage from the peak value detection circuit, and a timer that inputs the signal from the comparison circuit and outputs the signal after a predetermined time. The reason is that a circuit is provided.

E. In the effect detection circuit, the signal waveform from the rectifier circuit is averaged by an average value circuit, and its peak value is detected by a peak value detection circuit. The output voltage from the average value circuit and the divided voltage obtained by dividing the output voltage from the peak value detection circuit are compared and determined in a comparator circuit, and an open phase is detected from the difference in voltage waveform between each terminal of the three phases. Then, the signal from the comparator circuit activates the tripping mechanism via the timer circuit, opening the electrical circuit.

To Examples.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a three-phase three-wire circuit breaker with an open-phase protection function according to the present invention will be described based on the drawings.

In FIG. 1, E is a circuit breaker connected between the input/output terminals of the R-phase line, S-phase line, and T-phase line and the three-phase induction motor M; B and C are load lines, a. b and C are detection lines.

FIG. 2 is an electrical circuit diagram of the circuit breaker E.
2 is a power supply circuit, and 2 is a detection circuit.

The power supply circuit 1 consists of a rectifier circuit 3 and a constant voltage circuit 4 connected thereto.The rectifier circuit 3 consists of a rectifier stack 3a and a diode, etc., and the constant voltage circuit 4 consists of a diode, a transistor, etc. It is connected to the time limit circuit 9.

On the other hand, the detection circuit 2 includes a rectification circuit 5, an average value circuit 6, a peak value detection circuit 7, a comparison circuit 8, and a time limit circuit 9. The rectifier circuit 5 is composed of a rectifier stack 3a, a guioto, etc., and an average value circuit 6 and a peak value detection circuit 7 are connected in parallel to this rectifier circuit 5, both are connected to a comparison circuit 8, and the comparison circuit 8 has a time limit. Connected to circuit 9. The average value circuit 6, the peak value detection circuit 7, the comparison circuit 8, and the time limit circuit 9 are all constructed from ICs. A thyristor 10 is connected to the time limit circuit 9, and the thyristor 1
0 is connected to a trip coil 11 that constitutes a part of a trip mechanism (not shown).

In this way, the power supply circuit 1 and the detection circuit 2 use rectifier stacks, diodes, transistors, ICs, etc., so they are small and lightweight, making them suitable for mass production, and since there are few contacts, they have good vibration resistance, which prevents failures. less and has a longer lifespan.

The circuit breaker configured as described above detects an open phase as follows. That is, when the electric motor M is operating normally, the entire voltage from the rectifier circuit 5 as shown in FIG. A waveform 20 is output, the full waveform 20 is averaged in the average value circuit 6 as shown in FIG. 3(b), and the average waveform 21 is outputted to the comparison circuit 8. On the other hand, the full-wave waveform 20 is output to the peak value detection circuit 7, and the peak value detection circuit 7
As shown in Figure (C), a peak value detection waveform 22 is detected and output to the comparator circuit 8 after voltage division. In the comparison circuit 8, as shown in FIG. 3(d), the threshold voltage, which is the voltage obtained by dividing the voltage in FIG. 3('C), is set as a reference value 23, and this is compared with the average waveform 21. As shown in FIG. 3(e), when the value of the average waveform 21 is larger than the reference value 23 (normal), the signal is output to the thyristor 10. Since the thyristor 10 does not conduct current to the trip coil l1 according to the signal, the trip coil 11 is not activated and the trip device is not activated.

In addition, if the electric motor M does not operate normally and has an open phase, the rectifier circuit 5 outputs a voltage across the entire waveform 24 as shown in FIG. 4(a).
is output, and its entire waveform 24 is averaged in the average value circuit 6 as shown in FIG. 4(b), and the average waveform 25 is
is output to the comparison circuit 8. On the other hand, the full waveform 24 is outputted to the peak value detection circuit 7,
As shown in FIG. 4(c), the peak value detection waveform 26 is detected and output to the comparison circuit 8 after voltage division.

In the comparator circuit 8, as shown in FIG. 4(d),
The threshold voltage, which is the voltage obtained by dividing voltage c), is set as a reference value 27, and this is compared with the above average waveform 25, and as shown in FIG. 4(e), the value of the average waveform 25 is equal to the reference value 2.
If it is smaller than 7 (in the case of an open phase), the signal is output to the thyristor 10. The thyristor 10 causes current to flow through the trip coil 11 in accordance with the signal, so the trip coil 11 is activated and the electric path is opened by the trip device.

The reference value can be set because the peak value is the same in normal times and in open phase times. This reference value corresponds to the middle potential between the normal state and the open phase state.

G. Effects of the Invention As explained above, the three-phase three-wire type circuit breaker with phase loss protection function according to the present invention includes four average value circuits, a peak value detection circuit, a comparison circuit, etc. in the detection circuit, and Since it is made of semiconductor and opens the circuit by detecting phase loss, it is suitable for mass production, and since there are few contacts, it has good vibration resistance, fewer failures, and is highly reliable.
Since open phase is detected based on the difference in voltage waveforms between the phase terminals, the open phase protection function can be provided without limiting the model, making it extremely practical.

[Brief explanation of drawings]

Fig. 1 is a block diagram in which a three-phase three-wire circuit breaker with open-phase protection function according to the present invention is connected to a three-phase induction motor, Fig. 2 is an electric circuit diagram of the circuit breaker, and Fig. 3 (a). (b), (c)
, (d) and (e) are diagrams showing the full waveform, average waveform, peak waveform, reference voltage, and waveform comparison state, respectively, during normal operation. , (d) and (e
) are diagrams showing the full waveform, average waveform peak waveform, reference voltage, and state of waveform comparison at the time of phase loss, respectively. l...power supply circuit, 2...detection circuit, 3, 5...rectifier circuit, 3a...rectifier stack, 4...constant voltage circuit, 6...average value circuit, 7...peak value detection circuit, 8...・Comparison circuit,
9... Time limit circuit, 10... Thyristor, 11... Trip coil 20, 24... Full wave waveform, 21, 25... Average waveform, 22, 26... Peak value detection waveform, 23, 27...
・Reference value, A, B, C... Load line, E... Breaker, M...
・3-phase induction motor, R...R phase line, S...S phase line, T...
・T phase line, a, bC...detection line

Claims (1)

[Claims] In the circuit breaker equipped with an open-phase detection mechanism, the open-phase detection mechanism includes a power supply circuit and a detection circuit, the power supply circuit is provided with a rectification circuit and a constant voltage circuit, and the detection circuit includes a rectification circuit and a rectification circuit. An average value circuit that averages the signal waveform from the rectifier circuit, a peak value detection circuit that detects the peak value of the signal waveform, and separates the output voltage from the average value circuit and the output voltage from the peak value detection circuit. A 3-phase 3-wire shutoff system with an open-phase protection function that is equipped with a comparison circuit that compares and judges the divided voltages and a timer circuit that inputs the signal from the comparison circuit and outputs the signal after a predetermined period of time. vessel.