JPH07245938A - Failure detector for element in semiconductor ac switching device - Google Patents

Abstract

PURPOSE:To provide a detector for detecting open circuit, as well as short circuit, of a semiconductor switching element positively. CONSTITUTION:A semiconductor AC switching device 21 controls power supply from a main circuit 24 to an AC motor 26 by turning thyristors 22, 23 ON/OFF through a control circuit. A decision circuit 31 detects an offset voltage of an LFP30 based on a detected signal Sd of load current obtained through a current transformer 28, a full-wave rectifier circuit 29, and a low-pass filter (LPF) 30 upon turn OFF of the thyristors 22, 23 and corrects the subsequent detection signal Sd. If the corrected detection signal Sda is higher than a predetermined level when an OFF control signal is outputted, the decision circuit 31 makes a decision that a short circuit fault has occurred. If the signal Sd is zero when an ON control signal is outputted, a decision is made that the thyristor is open circuited and the faulty thyristor is determined based on the half-wave conduction state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor AC switching device for detecting a failure state of a semiconductor switching element in which the power supply from an AC power source to a load is controlled by a switch circuit using the semiconductor switching element. Device failure detection device.

[0002]

2. Description of the Related Art An example of this type is shown in FIG. That is, the semiconductor AC switch device 1 connects the two thyristors 2 and 3 in an anti-parallel connection, and connects the main circuit 4 of the three-phase AC power source to the AC motor 6 via the circuit breaker 5 and the thyristors 2 and 3. (Only one phase is shown). In the device failure detection device 7, the current transformer 8 detects the load current flowing through the thyristors 2 and 3. This detected current signal is input to the comparator 11 via the rectifier circuit 9 and the low-pass filter 10, and the current reference value signal S for failure determination set by the reference voltage setting device 12 is input.
When k is exceeded, an "H" level signal is output to the AND circuit 13. An ON control signal Son and an OFF control signal Soff given to the thyristors 2 and 3 are input to the AND circuit 13 from an unillustrated control circuit via the inverter circuit 14.

In the semiconductor AC switch device 1 having the above structure, the thyristors 2 and 3 are turned on by the "H" level ON control signal Son and turned off by the "L" level OFF control signal Soff from the control circuit. The on / off control signals Son and Soff are also input to the inverter circuit 14. When the thyristors 2 and 3 are turned on, power is supplied from the AC power supply to the AC motor 6.

Now, the state in which the control circuit outputs the "L" level off control signal Son, that is, the thyristor 2,
In a state in which the inverter 3 is controlled to be in the off state, the inverter 14 outputs a signal at the "H" level. At this time, the thyristors 2 and 3 are in the off state, so the current transformer 8
Since the detected current is zero and the comparator 11 outputs a signal of "L" level, the AND circuit 13 outputs a signal of "L" level indicating a normal state.

However, when the thyristors 2 and 3 have a short circuit failure, the control circuit causes the thyristors 2 and 3 to be disconnected.
However, the AC motor 6 is energized even though the OFF control signal Soff is output. At this time, the current transformer 8
Output signal S of the low-pass filter 10 with respect to the detection current of
When d exceeds the current reference value signal Sk, the comparator 1
1 outputs an "H" level signal, the AND circuit 1
Reference numeral 3 is an "H" level failure determination signal Sp indicating a failure state.
Will be output. As a result, the thyristors 2, 3
Is detected.

[0006]

By the way, in the above configuration, when the low-pass filter 10 including the operational amplifier is used, a signal obtained by drifting the offset voltage generated by the operational amplifier with respect to the input signal is used. May be output. Therefore, the comparator 11
A signal which changes by the offset voltage generated by the low-pass filter 10 with respect to the level of the current detected by the current transformer 8 is input to.

Thus, for example, even when the load current level does not actually reach the failure level, it is erroneously determined to be in the failure state, or conversely, when the load current level exceeds the failure level. However, problems such as erroneous determination as a normal state may occur.

Further, in the conventional structure, since only the short-circuit failure state of the thyristors 2 and 3 can be detected, it is possible to cope with a failure in which the thyristors 2 and 3 are in the open state. Instead, it was necessary to separately provide a detection device.

The present invention has been made in view of the above circumstances, and an object thereof is to correct an output signal even if the output signal drifts due to an offset voltage generated inside the filter, thereby enabling accurate failure detection. An object of the present invention is to provide an element failure detection device for a semiconductor AC switch device that can be performed and can determine a failure state other than a short circuit failure.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a semiconductor switching element provided in a main circuit for supplying AC power to a load is controlled by an ON control signal and an OFF control signal output from a control means. The present invention is intended for an element failure detection device of a semiconductor AC switching apparatus which is provided in a switch device and detects a failure of the semiconductor switching element, and a current detection for detecting a load current flowing through the semiconductor switching element. Means, a rectifying circuit for rectifying the detection output of the current detecting means, a filter for removing high frequency components from the rectifying output of the rectifying circuit, and an offset correction based on the output signal of the filter when the semiconductor switching element is in the OFF state. The offset setting means for setting a value and the level of the output signal from the filter are A corrected detection signal is corrected by offset correction value, characterized in was constructed by providing the determination means a failure of the semiconductor switching element based on the correction detection signal.

Further, the determination means is configured to determine a short circuit failure of the semiconductor switching element when the level of the correction detection signal exceeds a predetermined failure detection level in the output state of the off control signal by the control means. Good to do.

The determining means is configured to determine the open circuit failure of the semiconductor switching element when the level of the correction detection signal is a value corresponding to zero in the output state of the ON control signal by the control means. You can also

Further, the semiconductor switching element is
It is composed of two elements for conducting electricity in the forward direction and the reverse direction, and the judging means is arranged so that when the level of the correction detection signal exhibits a change corresponding to half-wave conduction of the AC power source, It may be configured to determine the failure of one of the semiconductor switching elements.

[0014]

According to the element failure detection device for a semiconductor AC switch device of the first aspect, the offset setting means outputs the output signal from the filter when the semiconductor switching element is in the OFF state, that is, when the load current is not flowing. Based on this, the offset correction value is obtained and set. Then, the determination means corrects the signal input from the filter by this offset correction value to make a correction detection signal, and makes a failure determination based on the correction detection signal. Therefore, the load current is detected by the offset generated in the filter. Even if the level fluctuates, a detection signal corresponding to an accurate load current can be obtained regardless of this, and the failure state of the semiconductor switching element can be reliably determined.

According to the element failure detecting device of the semiconductor AC switch device of the second aspect, the judging means is in a state in which the OFF control signal is outputted from the control means, that is, the semiconductor switching element is originally in the OFF state. When the level of the correction detection signal exceeds the failure detection level, the semiconductor switching element causes a short circuit failure, and the short circuit failure is determined as a load current is generated.

According to another aspect of the present invention, there is provided an element failure detecting device for a semiconductor AC switching apparatus, wherein the determining means is in a state in which an ON control signal is output from the control means, that is, the semiconductor switching element is originally in an ON state. When the level of the correction detection signal is a value equivalent to zero, the open failure is determined as the load current is not flowing because the semiconductor switching element is in the open failure state.

According to the element failure detection device of the semiconductor AC switch device of the fourth aspect, the determination means is turned off from the control means when one of the two semiconductor switching elements has a short-circuit failure. While the control signal is being output, the level of the correction detection signal exhibits a change corresponding to the half-wave energization state of the AC power supply, so that the short-circuit failure state of one semiconductor switching element is determined.

When any one of the semiconductor switching elements has an open circuit failure, the determination means determines that the level of the correction detection signal is the AC power source while the ON control signal is output from the control means. Since the change corresponding to the half-wave energization state is present, the open failure state of one semiconductor switching element is determined.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. That is, in FIG. 1 showing the electrical configuration, the semiconductor AC switch device 21 is connected to a three-phase AC power supply, and here, one phase is representatively shown. The two thyristors 22 and 23, which are semiconductor switching elements, are connected in anti-parallel so as to form current paths in opposite directions. The main circuit 24 connected to the AC power source includes a circuit breaker 25, thyristors 22 and 23.
Is connected to the AC motor 26, which is a load.
In addition, in this figure, a main circuit for one phase among those configured corresponding to the three-phase AC power supply is shown as a representative. The thyristors 22 and 23 are provided with ON control signals and OFF control signals from a control circuit (not shown) serving as control means.
"H" level and "L" level gate signals Son, Soff
Is given to control on / off.

The element failure detection device 27 is constructed as follows. The current transformer 28 as the current detecting means is the thyristor 2
It is provided in the energization path from 2, 23 to the AC motor 26. The output terminal of the current transformer 28 is connected to a low-pass filter 30 via a full-wave rectifying circuit 29 as a rectifying means. The low-pass filter 30 is a general one including an operational amplifier, and cuts off high-frequency components from the output signal of the full-wave rectifier circuit 29 to determine the detection signal Sd as the determination circuit 3.
Give to one.

The determination circuit 31 having a function as an offset setting means and a determination means is composed of a microcomputer, a ROM, a RAM, an A / D converter, etc., and stores an offset setting program and a failure determination program. . A control circuit is connected to the determination circuit 31 via an inverter circuit 32, and gate signals Son and Soff to be given to the thyristors 22 and 23 are input.

Next, the operation of this embodiment will be described with reference to the flowcharts of FIGS. 2 and 3. (1) Setting of Offset Voltage Value The control circuit gives the “H” level gate signal Son to the thyristors 22 and 23 to turn them on, and at the same time, sets them to “L”.
A level off control signal Soff is given to turn off. Then, the on / off control signal Son,
Soff is also given to the determination circuit 31. When the thyristors 22 and 23 are turned on and the AC motor 26 is energized from the main circuit 24 side, the load current thereof is detected by the current transformer 28 and full-wave rectified by the full-wave rectification circuit 29. After that, low-pass filter 3
The detection signal Sd from which the high frequency component is removed by 0 is input to the determination circuit 31.

The determination circuit 31 executes the offset setting program shown in FIG. 2 to set the offset voltage value ΔSv immediately before the control circuit gives the thyristors 22 and 23 the “H” level gate signal Son. Like The determination circuit 31 first A / D-converts and inputs the detection signal Sd input from the low-pass filter 30 (step S1), and then sets the value of the repeat counter N to "1" (step S2). At the same time, the value of the variable P is cleared to "0" (step S3).

Next, the judgment circuit 31 adds the digital value Sv of the input offset voltage signal to the variable P (step S4), and adds the value of the counter N by "1" (step S5). Then, it is judged whether or not the value of the counter N has reached a predetermined number of repetitions n (step S6), and "N
In the case of "O", the process returns to step S4 to repeat the above-described addition processing, and thereafter, steps S4 to S6 are repeated until the value of the counter N reaches the number of repetitions n. When the determination circuit 31 determines “YES” in step S6, in a succeeding step S7, the value of the addition result P of n times is divided by n to calculate an average value per one time, and this is calculated as an offset voltage value. Set as signal ΔSv and terminate the program.

As a result, when the thyristors 22 and 23 are off, that is, when the load current is not flowing, the level of the offset voltage value, which is the level of the voltage input from the low-pass filter 30 to the determination circuit 31, is offset. That is, the determination circuit 31 detects the voltage value signal ΔSv.

(2) Failure Detection Operation Next, the control circuit causes the thyristors 22 and 23 to have "H",
While the "L" gate signals Son and Soff are being output, the determination circuit 31 always determines the operating states of the thyristors 22 and 23 according to the failure determination program shown in FIG. In addition, here, the thyristor 22,
23 is (a) normal, (b) one or both short-circuit faults, (c) both open (open) faults, and (d) one open fault. Explain.

(A) Normal state That is, first, in a state in which the control circuit outputs the "H" level gate signal Son, which is an ON control signal, to the thyristors 22 and 23, the determination circuit 31 executes the program. When it starts, the signal from the low-pass filter 30 is input and converted into the digitized detection signal Sd by the A / D converter (step T1), and subsequently, the offset voltage value signal ΔSv is subtracted from the detection signal Sd. The correction is made (step T2). As a result, the low-pass filter 3
Since the offset voltage of the detection signal Sd input from 0 is corrected, the correction detection signal Sda corresponding to the accurate current value corresponding to the load current detected by the current transformer 28.
Will be able to get.

Next, the judgment circuit 31 judges whether or not the signal output from the control circuit to the thyristors 22 and 23 is the "L" level gate signal Soff corresponding to the OFF control signal. Now, from the control circuit, the gate signal S
Since the state in which off is output is considered, the determination circuit 31 is given a signal of “H” level via the inverter circuit 32, and therefore, “YES” here.
Then, the process proceeds to step T4, and the thyristor 22,
It is determined whether or not 23 is out of order.

When the thyristors 22 and 23 are normal, they are in the off state because the gate signal Soff is given from the control circuit, and the level of the correction detection signal Sda detected by the determination circuit 31 corresponds to zero. Since it is a value to be performed, the program is ended by judging “NO”.

Next, while the control circuit is outputting the "H" level gate signal Son, which is the ON control signal, the determination circuit 31 determines the load current through steps T1 and T2 in the same manner as described above. Corresponding correction detection signal Sd
When "a" is obtained, it is determined "YES" in the following step T3, and the process proceeds to step T5. Here, the determination circuit 31
Since it is not in the half-wave energization failure state, it is determined to be "NO" and the process proceeds to step T6.
Since the value of is not zero, it is determined to be "NO" and the program ends.

(B) One or Both Short Circuit Faults Next, if even one of the thyristors 22 and 23 has a short circuit fault, the control circuit outputs the "H" level gate signal Soff. However, since the load current is being applied to the AC electric motor 26, the determination circuit 31 proceeds to step T4 through step T3, and the value of the correction detection signal Sda Is above a predetermined level, the determination is “YES”, the process proceeds to step T7, and the failure determination signal Sp is output. When the control circuit receives the failure determination signal Sp, the control circuit shuts off the power supply to stop the energization control to the AC motor 26, and notifies the user of the failure state by a display operation or a notification operation. The treatment can be reliably performed.

(C) Both Open Failures When both thyristors 22 and 23 have an open failure, it is in a state where the control circuit outputs the "H" level gate signal Son. Nevertheless, the load current is no longer applied to the AC motor 26. Therefore,
After the determination circuit 31 proceeds from step T3 to step T5 and determines “NO”, the correction detection signal Sda indicates that the level of the load current is zero at step T6. The determination is made, the process proceeds to step T7, the failure determination signal Sp is output, and the program ends.

(D) One of the thyristors 22 and 23 has an open circuit failure. Next, when one of the thyristors 22 and 23 has an open circuit failure, the control circuit outputs the "H" level gate signal Son. In this state, the AC motor 26 is energized in only one direction, and the load current is in a half-wave energized state. Therefore, when the determination circuit 31 goes to step T4 after step T3, the determination circuit 31 sets "YE
S ”, the process proceeds to step T7, where the failure determination signal Sp
Will be output and the program will be terminated.

According to this embodiment, the decision circuit 3
1, the output signal Sv of the low-pass filter 30 in the off state of the thyristors 22 and 23 is set a predetermined number of times (n times).
Since the offset voltage value signal ΔSv of the low-pass filter 30 is detected and the average value thereof is calculated and the detection signal Sd is corrected by the offset voltage value signal ΔSv to obtain the corrected detection signal Sda, the AC motor 26 It is possible to accurately detect the load current flowing through the device and always make a correct failure determination.

Further, according to this embodiment, the determination circuit 31 causes the correction detection signal Sd in the output state of the "H" level gate signal Son which is the ON control signal from the control circuit.
From a, the open failure of both is judged when the load current corresponds to zero, and the open failure of one is judged from the half-wave energized state.
It becomes possible to detect not only the short circuit failure of No. 3 but also one or both open failures.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. Semiconductor switching elements are transistors, FETs, IGs
BT or GTO may be used, or one bi-directional triac may be used. The AC power supply may be a single-phase AC power supply.

[0037]

As described above, according to the element failure detecting device for a semiconductor AC switch device of the present invention, the following effects can be obtained. That is, according to the element failure detection device of the semiconductor AC switch device of claim 1,
The offset setting means sets an offset correction value based on the output signal of the filter in the off state of the semiconductor switching element, and the determination means sets the level of the output signal from the filter based on the correction detection signal corrected by the offset correction value. Since the failure of the semiconductor switching element is determined, even if the detection level of the load current fluctuates due to the offset generated in the filter, the detection signal corresponding to the accurate load current can be obtained regardless of this. Therefore, there is an excellent effect that the failure state of the semiconductor switching element can be reliably determined.

According to the element failure detection device of the semiconductor AC switch device of the second aspect, the level of the correction detection signal exceeds the failure detection level while the determination means outputs the OFF control signal from the control means. In this case, since the failure determination signal is output, there is an excellent effect that the short-circuit failure state of one or both of the semiconductor switching elements can be determined.

According to the element failure detection device of the semiconductor AC switch device of the third aspect, the level of the correction detection signal is a value corresponding to zero when the determination means outputs the ON control signal from the control means. In this case, since the failure determination signal is output, it is possible to determine that the load current is not flowing, that is, the semiconductor switching element is in the open failure state.

According to another aspect of the semiconductor AC switch device element failure detection device of the present invention, when the level of the correction detection signal is changed by the determination means, the failure occurs when the AC power supply has a half-wave energized state. Since the determination signal is output, there is an excellent effect that the failure state can be determined even when one of the semiconductor switching elements has an open failure.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart of an offset setting program

FIG. 3 is a flowchart of a failure detection program.

FIG. 4 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

21 is a semiconductor AC switching device, 22 and 23 are thyristors (semiconductor switching elements), 24 is a main circuit, 25 is a circuit breaker, 26 is an AC motor (load), 27 is an element failure detection device, and 28 is a current transformer ( Reference numeral 29 is a full-wave rectifying circuit (rectifying means), 30 is a low-pass filter (filter), 31 is a judging circuit (offset setting means, judging means), and 32 is an inverter circuit.

Claims (4)

[Claims] 1. A semiconductor AC switching device, wherein a semiconductor switching element provided in a main circuit for supplying AC power to a load is controlled by an ON control signal and an OFF control signal output from a control means, and the semiconductor switching device is provided. In a device for detecting a failure of a switching element, a current detection means for detecting a load current flowing through the semiconductor switching element, a rectification circuit for rectifying a detection output of the current detection means, and a rectification circuit for the rectification circuit. A filter for removing high frequency components from the output, an offset setting means for setting an offset correction value based on the output signal of the filter in the off state of the semiconductor switching element, and a level of the output signal from the filter for the offset correction value. To make a correction detection signal, and based on the correction detection signal Element fault detection apparatus of a semiconductor AC switch device characterized by comprising a determination means for determining failure of the semiconductor switching elements. 2. The determining means determines a short-circuit failure of the semiconductor switching element when the level of the correction detection signal exceeds a predetermined failure detection level in the output state of the OFF control signal by the control means. An element failure detection device for a semiconductor AC switch device according to claim 1. 3. The determination means determines an open circuit failure of the semiconductor switching element when the level of the correction detection signal is a value equivalent to zero in the output state of the ON control signal by the control means. An element failure detection device for a semiconductor AC switch device according to claim 1 or 2. 4. The semiconductor switching element is composed of two elements for energizing in a forward direction and a reverse direction, and the determining means determines that the level of the correction detection signal is equal to a half-wave energization of the AC power supply. When a corresponding change occurs, the
The device failure detection device for a semiconductor AC switch device according to claim 1, wherein a failure of one of the semiconductor switching devices is determined.