JPS637164A - Nonconduction detector for thyristor - Google Patents

Abstract

PURPOSE:To effectively prevent a nonconduction detector for a thyristor from erroneously detecting by judging that the detector has no malfunction and the thyristor is nonconductive on conditions that a photodetector receives the light of a light emitting element for intermittently emitting a light synchronously with the specific period of an AC power source to produce an output. CONSTITUTION:When a light emitting element 7 intermittently emits light in response to the repetition of conduction and nonconduction of a thyristor 2 synchronous with the specific period of an AC power source 1, counters 11, 12 are alternately reset by the output change of the photodetector 9 which receives the light. At this time, the output of an AND circuit 14 is '1'. When any of components 3-10 becomes defective, the photodetector 9 cannot receive the light, and the counter 11 or 12 is not reset. When the counted value of the counter 11 or 12 becomes a predetermined value or more, the output of the AND circuit 14 is intermittently interrupted to judge the malfunction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a non-conduction detector for a thyristor.

[Conventional technology]

FIG. 3 is a schematic diagram showing a conventional thyristor non-conduction detector disclosed in, for example, Japanese Utility Model Application Publication No. 53-81557.
In the figure, 1 is an AC power supply, 2 is a silice, 3 is a fixed resistor, 6 is a diode, 7 is a light emitting element, 8 is an optical fiber, and 9 is a light receiving element.

Next, the operation will be explained. When the thyristor 2 is conductive, the series circuit of the fixed resistor 3 and the light emitting element 7 is short-circuited by the thyristor, and the light emitting element does not emit light. and,
When the thyristor 2 becomes non-conductive, the output voltage of the AC power supply 1 is applied to the series circuit, and the light emitting element 7 emits light. By introducing light from the light emitting element 7 to the light receiving element 9 via the optical fiber 8, a detection signal indicating that the thyristor 2 is non-conducting is obtained from the light receiving element 9.

[Problem that the invention seeks to solve]

Conventional thyristor conduction detectors are configured as described above, so if, for example, the light receiving section including the light receiving element fails in a state where it is receiving light even though it is not receiving light, the thyristor continuity detector is configured as described above. Continuity.

There is a problem in that non-conduction is erroneously detected regardless of non-conduction.

This invention was made to solve the above-mentioned problems, and on the condition that it continues in synchronization with the cycle of the AC power supply, it can be mistakenly assumed that there is no abnormality in the detector and that the thyristor is non-conducting. The purpose of the present invention is to obtain a thyristor non-conduction detector that determines when the signal is off.

[Means for solving problems]

The thyristor non-conduction detector according to the present invention includes a light receiving element that receives light from a light emitting element connected in parallel with the thyristor, and outputs an output when the count value of clock pulses exceeds a certain value, and outputs an output I01 of the light receiving element. a first counter that is reset; a second counter that is output when the count value of clock pulses exceeds a certain value; and that is reset when the output of the light receiving element is "1"; The device includes an OR circuit that logics the counter output, and an AND circuit that logics the output of this OR circuit and the output of the light receiving element.

[For production]

First in this invention. The second counter is activated by the output of the light receiving element that continues in synchronization with a specific cycle of the AC power supply.
Since it is reset before the count value exceeds a certain value, the output is maintained at zero, and the output of the OR circuit also becomes zero. Therefore, when the light emitting element emits light due to non-conduction of the thyristor,
After receiving the output of the light receiving element, the output of the AND circuit is I 1 m
Tona υ, Cyrisk non-continuity detector is normal, and
To accurately determine that a thyristor is non-conducting.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, in which the same parts as in Fig. 3 are given the same reference numerals,
4.5 is a fixed resistor, 6-1 to 6-4 are diodes, 1
0 is a clock pulse oscillator, 11 is a first counter that counts clock pulses from the clock pulse oscillator 10, outputs a signal when the counted value exceeds a certain value, and is reset when the input signal of the R terminal becomes zero; 12 13 is a second counter which counts clock pulses from the clock pulse oscillator 10 and outputs a signal when the counted value exceeds a certain value, and is reset when the input signal at the R terminal becomes zero;
an OR circuit that inputs the outputs of the second counters 11 and 12;
14 is a circuit for inputting the output of the OR circuit 13 to a negative terminal and the output of the light receiving element 9 to another terminal.

Figure 2 is a time chart diagram for explaining the operation of Figure 1 above. In the second oral history), e is an AC voltage waveform, f
, g indicate the voltage level at which the light emitting element 7 stops emitting light.

FIG. 2(b) shows that the period during which the light emitting element emits light according to the voltage level f2g is 1 high", and when g<e<f, the period is 10".

The signal shown in FIG. 2(b) is the first signal. second counter 1
The count value of 1.12 changes as shown in Figure 2 (c) and (d).

Next, the operation will be explained. Thyristor 2 is AC power supply 1
When the light emitting element 7 emits light intermittently in response to repeating conduction and non-conduction in synchronization with a specific cycle of the first . The second counters 11,12 are reset alternately. For this reason, 1.
The second counters 11, 12 never exceed a certain value.

Therefore, the output of the OR circuit 13 is "0", the thyristor 2 becomes non-conductive, the light emitting element 7 emits light, and the output of the light receiving element 9 that receives the light becomes 11'.
The output of the D circuit 14 becomes I+11, and it can be determined without error that the thyristor non-conduction detector is normal and the thyristor is non-conductive.

On the other hand, if a malfunction such as a failure occurs in any of the components 3 to 10 in FIG. Therefore, the second counter 2 is not reset 9 and its count value exceeds a certain value.

Also, contrary to the above, if a failure occurs in the light receiving element 9 (for example, a failure occurs in a state in which it is receiving light even though it is not receiving light), the output of the light receiving element is continuously set to @1''. In this case, the first counter 11 is not reset and its count value exceeds a certain value.

As mentioned above, the first. When the counted value of one or both of the second counters 11 and 12 exceeds a certain value, the OR circuit 13
An output is generated in the AND circuit 14, and no output is generated continuously in the AND circuit 14. Therefore, the output of the OR circuit 13 may be used, or since the output of the AND circuit 14 is not generated continuously,
It can be determined that the thyristor 2 is conducting or that there is an abnormality in the thyristor non-conducting detector.

Note that in the above embodiments, the light emitting element and the optical fiber are used.

Although a light-receiving element is shown, a 7-oto coupler may be provided in place of these elements. Further, although a single-phase circuit is shown in the above embodiment, the same effect as in the above embodiment can be obtained even as a non-conduction detector for each thyristor of a three-phase full-wave rectifier circuit.

〔Effect of the invention〕

As described above, according to the present invention, on the condition that the light receiving element receives and outputs the light of the light emitting element that emits light intermittently in synchronization with a specific cycle of the AC power supply, there is no abnormality in the detector and the thyristor is in a non-operating state. Since the structure is configured to judge that the thyristor is conductive, it is possible to obtain a highly reliable thyristor non-conduction detector that can reliably eliminate the problem of erroneously detecting non-conduction even though the thyristor is conductive. There is.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a thyristor non-conduction detector according to an embodiment of the present invention, FIG. 2 is a timing chart showing the circuit operation, and FIG. 3 is a schematic diagram of a conventional thyristor non-conduction detector. 2 is a thyristor, 7 is a light emitting element, 9 is a light receiving element, 10 is a clock pulse oscillator, 11 is a first counter, 12 is a second counter, 13 is an OR circuit, and 14 is an AND circuit. In addition, in the figures, the same numerals indicate the same or equivalent parts 0 Patent applicant Mitsubishi Electric Co., Ltd. agent Patent attorney 1) Hiroshi Sawa (2 others) to tltz t3 Procedure corrector (spontaneous)

Claims (1)

[Claims] A thyristor to which an alternating voltage of a specific period is applied, a light emitting element connected in parallel with the thyristor, a light receiving element receiving light from the light emitting element, and a clock pulse from a clock pulse oscillator are counted to obtain a count value. a first counter that outputs an output when it exceeds a certain value and is reset with the output of the light receiving element "0"; and a first counter that counts the clock pulses and outputs when the counted value exceeds a certain value and outputs the output of the light receiving element "1".
”; and a second counter that is reset by
A thyristor non-conduction detector comprising: an OR circuit that logics the output of a counter; and an AND circuit that outputs "1" when the output of the OR circuit is "0" and the output of the light receiving element is "1".