JPH0611489Y2 - Fault detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a failure detection circuit for detecting a failure or abnormality of a contactor and preventing an abnormal operation of a load.

[Conventional technology]

Generally, when the main circuit element of the solid state contactor remains conductive or the contact of the contactor contactor is welded, turn off the control input signal unless the breaker trips due to an abnormal current. However, the load remains excited.

On the contrary, the main circuit element of the solid state contactor remains in a non-conducting state, or
When the contact of the contact reed contactor is dropped, even if the control input signal is turned on, the open phase operation is performed.

[Problems to be solved by the invention]

As described above, there is something that can detect with sufficient accuracy a failure in which the load is in the excited state even when the control input signal is turned off, or when the control input signal is turned on and the phase is lost. If so, the abnormal operation of the load can be prevented in advance. Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 62-84131 for detecting a failure of a non-contact contactor, failure detection of a non-contact contactor is detected by three inter-electrode voltage detecting means for each phase switching element. There was a method for detecting abnormalities by the output of this voltage detector and the operation signal of the contactor. In this method, however, in reversible connection, when one of the contactors is in operation, the S-phase pole of the other contactor in the stopped state is used. The inter-voltage also becomes 0, and the same phenomenon as switching element conduction is exhibited.
As a result, the failure detection circuit detects an abnormal state even if the contactor is normal, which causes a problem of malfunction.

The present invention has been made to solve the above-mentioned problems, and a contactor can detect a failure that does not respond to a control input signal with high accuracy, thereby preventing an abnormal operation of a load. The purpose is to provide a circuit.

[Means for solving problems]

The failure detection circuit according to the present invention includes a main circuit element provided in each phase of a three-phase power supply, a terminal voltage of the main circuit element of the first to third phases, an input side of the main circuit element of the first phase, and Based on the voltage detection means for detecting the interphase voltage between the output side of the main circuit element of the third phase and outputting a significant signal when the voltage is substantially zero, and the output of these voltage detection means and the control input signal. And a first to a fifth gate for performing a logical operation.

[Action]

In this invention, the NAND signal of the inter-terminal voltage signals of the first phase and the third phase in which the first gate is detected is obtained with respect to the output signal of each voltage detection means and the control input signal, while the second signal is obtained. When one of the first-phase voltage signal and the third inter-terminal voltage signal in which the gate is detected becomes significant, a negative product signal is obtained as if both become significant, and subsequently, the third gate is detected. When the exclusive OR signal of the voltage signal between the terminals of the main circuit element of the second phase and the output signal of the first gate is obtained, the fourth gate excludes the output signal of the second gate and the control input signal. The fifth gate receives one of the output signals of the fourth gate and the detected interphase voltage signal, and the third gate output signal and the detected signal. Negative product with the significant side of the interphase voltage signal as the other input The control circuit detects the conduction state due to the failure or welding of the main circuit element when the control signal is off, and detects the non-conduction state due to the failure or loss of the main circuit element when the control signal is turned on. Even if the forward and reverse operation is performed in combination, the same failure detection can be performed, and thus the abnormal operation of the load can be prevented.

〔Example〕

FIG. 1 shows an embodiment of the present invention together with an output circuit for outputting an abnormal signal and a signal input circuit for inputting a contactor control signal.

Here, the failure detection circuit is a bidirectional photocoupler O.
_{I R, OI S, OI T} , OI O, the current limiting resistor _{R R, R S,}
R _T , R _O , resistors R _{1 to} R ₉ , diodes D _{1 to} D ₅ , capacitor C ₁ , NAND gates A _{1 to} A ₃ , and exclusive OR gates B _{1 to} B ₃ . In this case, the load
Input terminals U, V, and W of (1) are connected to the R, S, and T phases of the three-phase AC power source through the main circuit elements (2 _R ), (2 _S ), and (2 _T ) of the solid-state contactor, respectively. Connected, current limiting resistor R
The series circuit of the light-emitting diode _R and the photocoupler OI _R are connected in parallel to the main circuit element (2 _R), a series circuit of the light emitting diodes of the same way a current-limiting resistor R _S and the photocoupler OI _S in other phases the main circuit element (2 _S), the series circuit of the light emitting diode current limiting R _T resistor photocoupler OI _T are respectively connected in parallel to the main circuit element (2 _T). Further, a series circuit of the current limiting resistor R _O and the light emitting diode of the photocoupler OI _O is connected between the R phase of the power supply and the input terminal W of the load (1). On the other hand, the photo-coupler OI _R, OI _S, O
The emitters of the transistors I _T and OI _O are grounded, and the collectors are connected to the DC power supply V _CC via resistors R ₁ , R ₂ , R ₃ and R ₄ , respectively. Then, the mutual junction of the transistor of photocoupler OI _R and the resistor R ₁ is connected to an input terminal of the NAND gate A _1, via the diode D ₂ is connected to a first input terminal of the NAND gate A _2, photo with mutual junction of the transistor and the resistor R ₃ of coupler OI _T is connected to the second input terminal of the NAND gate a _1, NAND gate a ₂ via the diode D ₁
Connected to the second input terminal of. The input terminals of the NAND gate A ₂ are connected to each other. Moreover, the mutual junction of the transistor of photocoupler OI _S and the resistance R ₂ is connected to a first input terminal of the exclusive OR gate B _1, NAND gate A ₁ output terminal of the second of the exclusive OR gate B ₁ Connected to the input terminal,
Further, the output terminal of the exclusive OR gate B ₁ is connected to the second input terminal of the NAND gate A ₃ via the diode D ₄ . On the other hand, the mutual junction of the transistor of photocoupler OI _O and the resistor R ₄ is connected to the second input terminal of the NAND gate A ₃ via a resistor R _5, via a resistor R ₆ of the NAND gate A ₃ It is connected to the first input terminal. An output terminal of the NAND gate A ₂ is connected to a first input terminal of the exclusive OR gate B _2, a second input terminal of the exclusive OR gate B ₂ is connected to the signal input circuit to be described later, further, the exclusive The output terminal of the OR gate B ₂ is connected to the first input terminal of the NAND gate A ₃ via the diode D ₃ . Next, the output terminal of the NAND gate A ₃ is connected to the first input terminal of the exclusive OR gate B ₃ whose second input terminal is grounded through the series circuit of the resistors R ₇ and R ₈ . A series circuit of a diode D ₅ and a resistor R ₉ is connected in parallel to the resistor R ₇ ,
A capacitor C _{1 is connected} between the mutual junction of the resistors R ₇ and R ₈ and the ground point
Are connected.

Next, the output circuit for outputting the abnormal signal is a resistor R ₁₀ ,
It is composed of R ₁₁ , a capacitor C ₂ , a thyristor SCR and an output relay RA. In this case, the thyristor SC
The cathode of R is grounded, and the anode is connected to the DC power supply V _CC via the output relay RA. The series circuit of a resistor R _10, R ₁₁ between the grounding point and the output terminal of the exclusive OR gate B ₃ described above are connected, together with the mutual junction of these resistors is connected to the gate of the thyristor SCR, It is grounded via a capacitor C ₂ .

Then, the signal input circuit contactor ON, ON in response to off-command, the off signal contacts a, resistors R ₁₂ to R _16, Bidirectional photocoupler OI _1, the capacitor C _3, NAND gate A _4, trigger circuit (3) and the transistor TR for driving the trigger circuit. In this case, the light emitting diode, the resistor R ₁₆ and the signal contact a of the bidirectional photocoupler OI ₁ are connected in series to the AC operation power source (4). The emitter of the transistor of the bidirectional photocoupler OI ₁ is grounded, the collector is connected to the DC power supply V _CC via the resistor R ₁₅ , and the exclusive OR which connects the input terminals of the resistors R ₁₄ and R ₁₃ to each other. It is connected to the base of the transistor TR via the gate A ₄ and the resistor R ₁₂ . The mutual junction point of the resistors R ₁₃ and R ₁₄ is grounded via the capacitor C ₃ . The emitter of the transistor TR is grounded, and the collector and the DC power supply V
_A trigger circuit (3) for applying a trigger pulse to the main circuit elements (2 _R ), (2 _S ), and (2 _T ) is connected to the _CC .

The operation of this embodiment configured as described above will be described below.

First, since the trigger circuit (3) does not operate when the signal contact a is off, the main circuit element of the solid state contactor is
_{(2 R), (2 S} ), (2 T) because in the OFF state, the bidirectional type photocoupler OI _R, OI _S, current flows through the light emitting diode of OI _T, photocoupler OI _R, OI _S, OI _T is the transistor off near an AC voltage between the main circuit elements as shown in FIG. 4 (a) passes through zero, turns on the outside of this, in the three-phase alternating current R, S, T phases each 120 ° the two-way type photocoupler OI _R in phase difference, OI _S, OI _T, repeatedly turned on and off.

At this time, the NAND gate A ₁ is connected to the bidirectional photocoupler O.
I _R, the exclusive OR gate B ₁ is outputting the H signal receives a signal OI _T outputs an H signal receiving signal of the NAND gate A ₁ of the signal and the bidirectional-type photo coupler OI _S. Whereas NAND gate A ₂ is Bidirectional photocoupler OI _R, diode D ₂ and transistor output OI _T,
The exclusive OR gate B ₂ receives the signal of the NAND gate A ₂ and the L signal of the input circuit NAND gate A ₄ and outputs the H signal while receiving the H signal through D ₃ . Nand Gate A ₃ is Exclusive OR Gate B ₁
And the H signal of the exclusive OR gate B ₂ outputs the L signal.

Exclusive OR gate B ₃ is the above NAND gate A ₃
The L signal is output according to the L signal. Therefore, the output relay RA of the output circuit does not operate and does not detect.

Next, when the signal contact a is off, when the main circuit element of the solid state contactor fails, that is, when the main circuit element fails in the conductive state, for example, when the R-phase main circuit element fails in the conductive state. as shown in FIG. 4 (b), the NAND gate a ₂ since the outputs of the H signal transistor of the bidirectional type photocoupler OI _R of R-phase in succession L
A signal is output and an abnormal signal L is output by the exclusive OR gate B ₂ , and the H signal of the NAND gate A ₃ drives the output relay RA of the output circuit by the H signal of the exclusive OR gate B ₃ .

Further, similar failure detection can be performed when the main circuit elements of the S phase and the T phase fail in the conductive state. If both R and T-phase main circuit elements fail in the conductive state, the fourth
As shown in FIG. (C), the NAND gate A ₂ is Bidirectional photocoupler OI _R, the output of NAND gate A ₃ output of the exclusive OR gate B ₂ which has output the signal receiving L signal OI _T is L signal H The signal becomes a signal, and the output H signal of the exclusive OR gate B ₃ causes the output relay RA of the output circuit.
Is driven. The same applies when all the main circuit elements of R, S, and T fail in the conductive state.

Then when the signal contact a is ON, FIG. 4 is a main circuit elements are all normal conditions of solid-state contactor (g) Bidirectional photo coupler as shown in OI _R, OI _S, the transistor is turned off the OI _T Thus, the output of the NAND gate A ₁ becomes the L signal and the output of the exclusive OR gate B ₁ becomes the H signal. The output of the NAND gate A ₂ becomes the L signal, the output of the NAND gate A ₄ of the input circuit becomes the H signal, and the output of the exclusive OR gate B ₃ becomes the L signal, and the output relay RA of the output circuit does not operate and does not detect.

Next, when the signal contact a is ON, if the main circuit element of the solid-state contactor fails, that is, if the main circuit element fails in the non-conducting state, as shown in FIGS. 4 (h) and 4 (i), for example, R If the phase fails in the non-conducting state NAND gate A ₁
The Bidirectional photocoupler OI _R, the signal receiving H signal OI _T is output, the exclusive OR gate B ₁ represents the NAND gate A ₁ of the signal and the bidirectional-type photo coupler O
The H signal is output according to the I _S signal. On the other hand, the output of the NAND gate A ₂ becomes the L signal, but the exclusive OR gate B ₂ inputs the signal of the NAND gate A ₂ and the H signal of the input circuit NAND gate A ₄ and outputs the L signal. Therefore, the output of the NAND gate A ₃ becomes As a result, the output of the exclusive OR gate B ₃ becomes the H signal, and the output relay RA of the output circuit is driven to perform the failure detection operation.

Then when the main circuit power supply off, when the signal contact a is turned on, NAND gate A ₁ is two-way type photocoupler OI _R, it becomes an L signal receives a signal OI _T, the exclusive OR gate B ₁ represents the NAND gate A ₁ H signal is output by the signal and the signal of the bidirectional type photocoupler OI _S. On the other hand, the exclusive OR gate B ₂ output also becomes L signal of the NAND gate A ₂ of the NAND gate A ₂ of the signal and the NAND gate A output of the L signal by L signal but is outputted Bidirectional photocoupler OI _{O 4} input circuits Since the output is H, the output of the NAND gate A ₃ becomes the L signal, the output of the exclusive OR gate B ₃ becomes the L signal, the output relay RA of the output circuit becomes inoperative, and no failure is detected.

Next, when two solid state contactors equipped with a failure detection circuit as shown in FIG. 2 are used for normal and reverse operation, as shown in FIGS. 3 (a) and 3 (b), the failure detection circuit (10) And (2
0) will be provided. In this case, when the forward rotation side contactor is in the ON state, the voltage between the main circuit elements of the reverse rotation side contactor in the OFF state is the phase voltage of TR, and the voltage between the main circuit elements of the S phase is the voltage of the forward rotation side contactor. Since the S-phase main circuit element is in the conductive state, the element-to-element voltage becomes zero. Therefore,
The condition that the failure detection circuit on the reverse rotation side does not operate with the inter-element voltage of the elements of the contact on the reverse rotation side unless the signal contact a ₂ on the reverse rotation side has an abnormality in the contactor. FIG. 4 (d) shows the operation of the detection circuit when the above voltage is applied to the reverse contactor. The NAND gate receives the outputs of the bidirectional photocouplers OI _R2 , OI _S2 and OI _T2 at the above voltage. A
The output of ₁ is H level, and the output of the exclusive OR gate B ₁ is L level because the output of the S-phase bidirectional photocoupler OI _S2 is H level. However, since the in-phase voltage is applied to the bidirectional photocoupler OI _O2 , a signal of H level is output, and therefore the input to the NAND gate A ₃ becomes H level. On the other hand, the output of the NAND gate A ₂ becomes H level and the output of the exclusive OR gate B ₂ becomes H level because the output of the NAND gate A ₄ of the input circuit is L level. Also, the output of the NAND gate A ₃ becomes L level,
In response to this, the output of the exclusive OR gate B ₃ becomes L level, and the output relay RA of the output circuit does not operate and no failure is detected.

If an abnormality occurs in the main circuit elements (2 _R1 ) and (2 _T1 ) of the R and T phases in this state, that is, if a failure occurs in the conducting state, a phase-to-phase short circuit occurs and Since it is considered that the main circuit is cut off, it is not necessary to detect the abnormality, but as shown in FIGS. 4 (e) and 4 (f), the failure can be detected even in this embodiment.

Thus, according to this embodiment, when the main circuit element of the solid-state contactor fails due to conduction or non-conduction, the main circuit can be cut off by giving a failure detection signal to the breaker, etc. The operation can be reliably prevented.

Although the solid-state contactor has been described in the above embodiment, it is needless to say that the present invention is not limited to this and can be applied to a contactor such as an electromagnetic contactor.

[Effect of device]

As will be apparent from the above description, according to the present invention, the four voltage detecting means and the five gates make it possible to establish a conduction state due to a failure or welding of the main circuit element when the control signal is turned off, and the control signal. It is possible to detect with high accuracy the non-conducting state due to the failure or loss of the main circuit element when the
This has the effect of preventing abnormal operation of the load in advance.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention together with a control signal input circuit and an abnormal signal output circuit of a contactor, and FIG. 2 is another main circuit system diagram to which the embodiment is applied, and FIG. Figures (a) and (b) are block diagrams showing the installation state when the same embodiment is applied to this system, and Figs. 4 (a) to (i) are waveform diagrams for explaining the operation of the same embodiment. Is. (2R), (2S), (2T): the main circuit element, (3): the trigger circuit (10), (20): the failure detection _{circuit, OI R, OI S, OI} T, OI O: photocoupler, _{A 1, A 2, A 3} : NAND _{gates, B 1, B 2, B} 3: exclusive OR gate. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. A method for detecting a failure of a main circuit element, which is provided for each phase of a three-phase power supply and is controlled to be turned on and off based on a control input signal, comprising: A voltage that detects the inter-terminal voltage and the inter-phase voltage between the input side of the main circuit element of the first phase and the output side of the main circuit element of the third phase, and outputs a significant signal when the voltage is substantially zero. One of the detecting means, the first gate that obtains a NAND signal of the detected first-phase and third-phase inter-terminal voltage signals, and the one of the detected first-phase and third-phase inter-terminal voltage signals A second gate that obtains a negative product signal when both become significant, and a detected inter-terminal voltage signal of the main circuit element of the second phase and an output signal of the first gate A third gate for obtaining an exclusive OR signal, and an output signal of the second gate A fourth gate for obtaining an exclusive OR signal of the control input signals, and one of the output signal of the fourth gate and the significant side of the detected inter-phase voltage signal is input, and the output signal of the third gate And a fifth gate for obtaining a NAND product signal by using the significant side of the detected interphase voltage signals as the other input, and setting the significant signal output from the fifth gate as a failure detection signal. Characteristic failure detection circuit.