JP2002329625A - Abnormality detector for differential transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality detector for differential transformer that can provide a plant using a differential transformer with a system of higher reliability by detecting the abnormal states, such as the disconnection, short- circuiting, etc., of two systems of secondary windings of the transformer at every secondary winding. SOLUTION: The abnormal states of the two systems of secondary windings of the differential transformer are detected at every secondary winding by respectively installing circuits which rectify the outputs of the secondary windings, arithmetic circuits which judge the levels of voltages V1 and V2 after rectification, and output circuits which output the judgment results to the secondary windings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential transformer abnormality detecting device for detecting an abnormal accident such as disconnection or short circuit of a differential transformer winding.

[0002]

2. Description of the Related Art Generally, 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. In addition, abnormal accidents such as disconnection and short-circuiting of the differential transformer winding have a great influence on other applications, and it is required to easily detect such accidents. FIG. 5 shows, for example,
This is a differential transformer failure detection device disclosed in Japanese Patent Application Laid-Open No. 2-16212. 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 output of each secondary winding is rectified by diode rectification circuits SR1 and SR2 and has voltages V1 and V2, respectively. The voltage V ₀ = V1 + V2 smoothed by the capacitor is further calculated by the arithmetic circuit 13
In comparison calculation a threshold Th1 shown in Fig. _4, V 0 <Th
When it becomes 1, the disconnection of the secondary winding is detected and output from the output circuit 14.

[0003]

In such a differential transformer failure detection device, the disconnection fault is detected by determining the sum of the rectified voltages of the secondary windings C21 and C22 based on the threshold voltage. In addition, it cannot be determined which of the secondary windings C21 and C22 is disconnected. Furthermore, the primary winding C1
This device is not suitable for applying to a system requiring higher reliability because it cannot detect whether or not there is a disconnection.

The present invention has been made to solve such a problem, and has been made in consideration of a primary winding of a differential transformer, a secondary winding of a differential transformer.
It is an object of the present invention to provide an apparatus that detects an abnormal failure such as disconnection for each secondary winding of a system and improves reliability.

[0005]

According to a first aspect of the present invention, there is provided a differential transformer abnormality detecting apparatus in which two secondary windings are provided with circuits for monitoring respective output voltages. When the output voltage becomes equal to or lower than a predetermined threshold value, it is output that an abnormality has occurred in any of the secondary windings.

According to a second aspect of the present invention, a monitoring circuit includes a rectifier circuit for outputting a secondary winding, an arithmetic circuit for calculating a voltage after the rectification, and an output circuit for outputting a determination result. Is what it is.

In a third aspect, a current detection circuit is provided on the input side of the primary winding.

According to a fourth aspect of the present invention, an AC oscillation circuit and a minute high-frequency output circuit are provided on the input side of the primary winding, and an output filter circuit is provided for each of the two secondary windings. And a detection circuit for a very high frequency, an arithmetic circuit for calculating the output of the very high frequency detection circuit, and an output circuit for outputting the result of the determination.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an abnormality detection device for a differential transformer according to a first embodiment of the present invention will be described 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. Numeral 10 is an abnormality detecting device for disconnection or short circuit of the differential transformer, and 11 and 12 are two-system secondary windings C21 and C21.
A rectifier circuit for rectifying the output of the inverter 22, the arithmetic circuit 13, the output circuit 14, and the oscillation circuit 15 constitute the abnormality detection device. The oscillation circuit 15 is an oscillation circuit for exciting the primary winding C1 of the differential transformer 50.

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 secondary winding C2 is driven in accordance with the amount of position movement of the iron core 40.
1, AC voltages are excited in C22, and the respective excitation voltages are rectified by rectifier circuits 11 and 12 to become V1 and V2 as shown in FIG. The arithmetic circuit 13 controls these voltages V
1 and V2 are determined by the threshold value Th2, and when the voltages V1 and V2 become equal to or less than Th2, the secondary winding C2
It is determined that there is an abnormal accident such as disconnection or short circuit of any one of C1 and C22, and the determination result is output by the output circuit 14.
Note that the threshold voltage T depends on the characteristics of the differential transformer 50.
Although h1 and Th2 cannot be uniquely set, the arithmetic circuit 13 can variably set the thresholds Th1 and Th2, so that it can flexibly cope with differential transformers having various characteristics. it can.

Embodiment 2 Embodiment 2 of the present invention will be described with reference to FIG. In FIG. 2, the oscillation circuit 15
The configuration is the same as that of the above-described first embodiment except that the current detection circuit 20 is provided between the primary winding C1 and the input side of the primary winding C1. 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 disconnection or short circuit occurs in the primary winding C1 of the dynamic transformer 50, the current is cut off, and the primary winding failure is detected from the current detection circuit 20 through the arithmetic circuit 13 and the output circuit 14. It becomes possible to detect. If the primary winding C1 is sound, the secondary windings C21 and C22 are used as described in the first embodiment.
The abnormality detection can also be performed for. That is, 1
An abnormality can be detected for each of the secondary windings C1, and the secondary windings C21 and C22.

Embodiment 3 FIG. Third Embodiment A third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the abnormality detection device 10 for a differential transformer includes two filter circuits 30, 31.
And a high-frequency detecting circuit 32, 33, a minute high-frequency output circuit 34, an oscillating circuit 15, an arithmetic circuit 13, and an output circuit 14. A very high frequency of, for example, 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. Circuit 3
Only high frequency components are extracted by filtering at 0 and 31, respectively, and output at high frequency detection circuits 32 and 33. Here, if the secondary windings C21 and C22 have an accident such as disconnection or short circuit, the high frequency components cannot be extracted naturally, and the extracted high frequency components are detected by the detection circuits 32 and 33. By doing so, the differential transformer 5
The presence or absence of an abnormality for each secondary winding of 0 can be grasped more reliably. That is, the servo control system and the process control system using the differential transformer 50 are generally large plant systems in many cases. For such a plant,
In some cases, a threshold voltage for control is set for each subsystem or all systems, but the setting operation is performed at the time of construction of a local plant, and requires complicated and busy work. Further, the threshold value setting varies depending on the coordinator, and is not always a value with little variation. Accordingly, there is a case where an apparent abnormality is detected even though the plant apparatus is normal. However, the third embodiment is not a device for determining a threshold level,
Since it is configured to output and detect a minute high frequency, excellent effects such as cost reduction due to shortening of on-site adjustment work and prevention of errors due to individual differences are exhibited.

[0013]

Since the present invention is a differential transformer abnormality detecting device employing the above-described configuration, the following effects can be obtained.

A circuit for monitoring the output voltage of each of the secondary windings is provided. When the output voltage of the secondary winding falls below a predetermined threshold, an abnormality occurs. Since it is determined and output, there is an excellent effect that an abnormal accident such as disconnection or short circuit of each of the two secondary windings can be detected.

In addition, since a current detection circuit is additionally provided on the input side of the primary winding, if a trouble such as disconnection or short circuit of the primary winding occurs, it is possible to detect an abnormality in the primary winding alone. In addition, the abnormality of the secondary winding is also added, that is, the primary,
This provides an excellent effect that an abnormality can be detected for each secondary winding.

Further, since two systems of the filter circuit and the detection circuit and the output circuit for outputting a very high frequency superimposed on the output of the oscillation circuit are provided, the abnormality detection can be set regardless of the original control operation. This provides an excellent effect that the presence or absence of an abnormality can be more reliably detected.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a differential transformer abnormality detection device according to a first embodiment of the present invention.

FIG. 2 is a configuration block diagram of a differential transformer abnormality detection device according to a second embodiment of the present invention.

FIG. 3 is a configuration block diagram of a differential transformer abnormality detection device according to a third embodiment 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 a threshold value for abnormality detection.

FIG. 5 is a configuration block diagram showing a conventional differential transformer failure detection device.

[Explanation of symbols]

10 abnormality detection device for differential transformer, 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 (4)

[Claims] 1. A differential transformer comprising a primary winding, two systems of secondary windings, and an iron core, wherein an output voltage of the secondary winding changes according to a position of the iron core. Is provided with a circuit for monitoring each output voltage, and the monitoring circuit determines that an abnormality has occurred in any of the secondary windings when the output voltage becomes equal to or less than a predetermined threshold value. An abnormality detection device for a differential transformer characterized by outputting. 2. A monitoring circuit comprising: a rectifier circuit for outputting a secondary winding;
2. The abnormality detection device for a differential transformer according to claim 1, comprising an arithmetic circuit for processing and determining the voltage after the rectification, and an output circuit for outputting the result of the determination. 3. The abnormality detection device for a differential transformer according to claim 1, wherein a current detection circuit is provided on an input side of the primary winding. 4. A differential transformer comprising a primary winding, two systems of secondary windings, and an iron core, wherein an output voltage of the secondary winding changes according to a position of the iron core. The input side is provided with an AC oscillation circuit and a minute high-frequency output circuit. Each of the secondary windings is provided with an output filter circuit and the minute high-frequency detection circuit. An abnormality detection device for a differential transformer, comprising: an arithmetic circuit for processing and judging the output of a detection circuit; and an output circuit for outputting the judgment result.