JP3786845B2 - Anomaly detector for differential transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality detecting device for a differential transformer for detecting an abnormal accident such as disconnection or short circuit of a differential transformer winding.
[0002]
[Prior art]
In general, a differential transformer is widely used as a position detector for detecting a position or an amount corresponding to a process amount in a servo control system or general process control. An abnormal accident such as a disconnection or a short circuit of the differential transformer winding has a great influence on others because of its use, and it is required to easily detect the accident. FIG. 5 shows a failure detection apparatus for a differential transformer disclosed in, for example, Japanese Patent Publication No. 52-16212. In the figure, the primary winding C1 of the differential transformer 50 is excited from the oscillation circuit 15, and the secondary windings C21 and C22 are excited according to the amount of position movement of the iron core 40. The outputs of the secondary windings are rectified by diode rectifier circuits SR1 and SR2 and have voltages V1 and V2, respectively. Further, the voltage V ₀ = V 1 + V ₂ smoothed by the capacitor is compared with the threshold value Th 1 shown in FIG. 4 by the arithmetic circuit 13, and when V ₀ <Th 1 is detected, the disconnection of the secondary winding is detected and the output circuit 14 Output.
[0003]
[Problems to be solved by the invention]
In such a differential transformer failure detection device, since the sum of the rectified voltages of the secondary windings C21 and C22 is determined by the threshold voltage to detect a disconnection accident, the secondary windings C21 and C22 are detected. It cannot be determined which of the windings is disconnected. Furthermore, it is not possible to detect whether or not the primary winding C1 is disconnected, and the device is not suitable for application to a system that requires higher reliability.
[0004]
The present invention has been made to solve such problems, and detects an abnormal failure such as disconnection for each primary winding and two secondary windings of a differential transformer to improve reliability. It is an object to provide an apparatus.
[0005]
[Means for Solving the Problems]
In the abnormality detecting device for a differential transformer according to the first invention, an AC oscillation circuit and a minute high-frequency output circuit are provided on the input side of the primary winding, and each of the two secondary windings An output filter circuit and a minute high frequency detection circuit are provided, and an arithmetic circuit for calculating the output of the minute high frequency detection circuit and an output circuit for outputting the determination result are provided.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
A differential transformer abnormality detection apparatus according to Embodiment 1 of the present invention will be described below with reference to FIGS.
In FIG. 1, 50 is a differential transformer, 40 is an iron core, C1 is a primary winding of the differential transformer, and C21 and C22 are secondary windings of the differential transformer. Reference numeral 10 denotes an abnormality detection device such as a disconnection or a short circuit of the differential transformer. Reference numerals 11 and 12 denote rectifier circuits that rectify the outputs of the two secondary windings C21 and C22. The arithmetic circuit 13, the output circuit 14, and the oscillation circuit The abnormality detecting device is constituted by 15. The oscillation circuit 15 is an oscillation circuit for exciting the primary winding C1 of the differential transformer 50.
[0007]
Next, the operation will be described in detail. The primary winding C1 of the differential transformer 50 is excited by the AC voltage output from the oscillation circuit 15, and the AC voltage is excited in the secondary windings C21 and C22 according to the amount of position movement of the iron core 40. The voltage is rectified by the rectifier circuits 11 and 12 and becomes V1 and V2 as shown in FIG. The arithmetic circuit 13 determines the level of these voltages V1 and V2 with a threshold value Th2, and when each of the voltages V1 and V2 becomes equal to or less than Th2, the secondary windings C21 and C22 are disconnected or short-circuited. It is determined that there is an abnormal accident, and the determination result is output by the output circuit 14. Although the threshold voltages Th1 and Th2 cannot be set uniquely depending on the characteristics of the differential transformer 50, various characteristics can be obtained by allowing the arithmetic circuit 13 to set the threshold values Th1 and Th2 variably. It is possible to flexibly cope with differential transformers with.
[0008]
Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same configuration as that of the first embodiment described above except that the current detection circuit 20 is provided between the oscillation circuit 15 and the primary winding C1, that is, on the input side of the primary winding C1. It is. As described above, the current detection circuit 20 for detecting the current flowing between the primary winding C1 of the differential transformer 50 and the oscillation circuit 15 for exciting the primary winding C1 is provided. When an abnormal trouble such as a disconnection or a short circuit occurs in the primary winding C1 of the dynamic transformer 50, the current is cut off, and the primary winding fails through the arithmetic circuit 13 and the output circuit 14 from the current detection circuit 20. It becomes possible to detect. When the primary winding C1 is healthy, the abnormality detection can be performed for the secondary windings C21 and C22 as described in the first embodiment. That is, it is possible to detect an abnormality in each of the primary winding C1 and the secondary windings C21 and C22.
[0009]
Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the differential transformer abnormality detection device 10 includes two systems of filter circuits 30 and 31 and high-frequency detection circuit circuits 32 and 33, a minute high-frequency output circuit 34, an oscillation circuit 15, an arithmetic circuit 13, and an output circuit 14. It consists of For example, a very high frequency of about several milliseconds is output from the output circuit 34 and superimposed on the oscillation circuit 15 for exciting the primary winding C1 of the differential transformer 50, and the outputs of the secondary windings C21 and C22 are filtered. Only high frequency components are extracted by filtering with the circuits 30 and 31, respectively, and output with the high frequency detection circuits 32 and 33. Here, when each secondary winding C21, C22 has an accident such as disconnection or short circuit, naturally the high frequency component cannot be extracted, so the extracted high frequency component is detected by the detection circuits 32, 33. By doing so, the presence or absence of abnormality for each secondary winding of the differential transformer 50 can be grasped more reliably.
That is, the servo control system and process control system in which the differential transformer 50 is used are generally large plant systems in many cases. In such a plant, a threshold voltage for control may be set for each sub-system or for all the systems, but the setting work is performed at the time of construction of the local plant, which is complicated and busy. It takes time and effort.
Also, the threshold setting is not necessarily a value with little variation because of individual differences among the adjusters. Accordingly, there may be a case where an apparent abnormality is detected even though the plant apparatus is normal. However, the third embodiment is not an apparatus for determining a threshold level, but is configured to output and detect minute high frequencies, so that it is excellent in cost reduction due to shortening of the field adjustment work and error prevention due to individual differences. Has an effect.
[0010]
【The invention's effect】
Since the present invention is a differential transformer abnormality detecting device adopting the configuration as described above, the following effects can be obtained.
[0011]
Two filter circuits and detection circuits, and an output circuit that outputs a minute high frequency superimposed on the output of the oscillation circuit, can be set for abnormality detection regardless of the original control operation, making it possible to more reliably detect the presence or absence of abnormality. It has an excellent effect of being able to be detected.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram of an abnormality detection device for a differential transformer according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of an abnormality detecting device for a differential transformer according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing the configuration of a differential transformer abnormality detection apparatus according to Embodiment 3 of the present invention;
FIG. 4 is a diagram illustrating a relationship between a voltage after rectification of a secondary winding of a differential transformer and an abnormality detection threshold value.
FIG. 5 is a configuration block diagram showing a conventional differential transformer failure detection apparatus.
[Explanation of symbols]
10 differential transformer abnormality detection device, 11, 12 rectifier circuit,
13 arithmetic circuit, 14 output circuit, 15 oscillation circuit, 20 current detection circuit,
30, 31 filter circuit, 32, 33 high frequency detection circuit,
34 high frequency output circuit, 40 iron core, 50 differential transformer,
SR1, SR2 Rectifier circuit, C1 primary winding, C21, C22 secondary winding.

Claims (1)

In a differential transformer having a primary winding, two secondary windings, and an iron core, and an output voltage of the secondary winding varies depending on the position of the iron core, an AC is provided on the input side of the primary winding. An oscillation circuit and a minute high frequency output circuit are provided, and each of the secondary windings is provided with an output filter circuit and a minute high frequency detection circuit, and outputs the minute high frequency detection circuit. An abnormality detection device for a differential transformer, comprising: an arithmetic circuit for determining processing; and an output circuit for outputting the determination result.

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