JPH0373807A - Instrument for measuring displacement - Google Patents

Abstract

PURPOSE:To immediately detect a failure such as disconnection by providing the displacement measuring instrument with a means for generating an alarm output when the sum of the induced voltages of a pair of secondary windings is dropped less than a regulated value. CONSTITUTION:Although respective outputs Es1, Es2, E's are values shown in the chart in accordance with replacement X, the cumulative output voltage E's always shows a fixed value independently of the displacement X as shown in the equation. The voltage E's which is the always fixed value at normal time independently of the displacement X is changed as follows at the time of accurence of a failure. Namely, when any point in the primary or secondary circuit is disconnected or a short circuit between (a) and (b) / (e) and (f), or a short circuit between (c) and (d)/ (e) and (f) is generated, E's =0 is formed. At the time of the short circuit between (c) and (d), E's =Es2 is formed, and at the time of the short circuit between (e) and (f), E's =Es1 is formed. Since the E's at the normal time has the relation of the equation II or III, the occur rence of a failure in a differential transformer 1 can be detected by detecting that the E's is dropped less than Ep (approximate to Vref) while monitoring the E's.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a displacement measuring device using a differential transformer.

(Prior art) For example, power generation turbine equipment is equipped with a single-chamber elongation monitoring device that constantly monitors the elongation of the turbine casing and detects abnormalities in order to prevent accidents such as damage to blades and failure to generate power. It is provided.

In addition, a monitoring device is provided for a regulating valve circuit that controls the amount of power generation so that the turbine can always operate efficiently.

Such monitoring of the expansion of the turbine casing and the regulating valve circuit is performed by measuring displacement using a solenoid type differential transformer.

In this displacement measuring device, a certain standard is stretched 01ll.
Then, the secondary voltage that changes with respect to the expansion of a single chamber or the control valve circuit can be extracted and used to directly drive an AC voltmeter, or the secondary voltage can be rectified and converted to a DC signal, and this can be used to measure displacement. It is used as a signal.

The circuit configuration of a conventional displacement measuring device is shown in FIG. 4(a),
The operation is shown in the graph of FIG. 4(b).

Using the center of the practical range as a reference point, the secondary voltage characteristics in the linear region can be approximately expressed mathematically as follows: Es l = (kx+
b) ・EbES 2 − (-kx 10b) −
EbES=ES1-ES2=2kx-Ep.

However, b-Ep is the voltage of the secondary winding when the displacement x = O (center).

Therefore, it can be seen that the secondary voltage ES increases or decreases in proportion to the displacement x.

Note that when the displacement x is negative, the phase of the AC signal is reversed.

<Problem to be solved by the invention> However, in such a conventional displacement measuring device, the change in the secondary voltage ES of the It device is caused by a disconnection R.
1 and when displacement x changes, so even if the secondary voltage ES is monitored, differential transformer 1 failure (coil, cable disconnection, loose contact, etc.) It was not possible to detect that this had occurred, and as a result, there was a risk that the operation of the turbine equipment would be disrupted.

This invention was made in view of the above problems,
The purpose of this is to use a displacement measurement device that measures the amount of displacement based on the difference in induced voltage between a pair of secondary windings installed in a differential transformer.
If a contact failure such as a cable breakage or a loose terminal occurs, it is possible to immediately detect this.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides an object based on the difference in induced voltage between a pair of secondary windings provided in a differential transformer. The displacement measuring device for measuring the amount of displacement is characterized in that it is provided with means for issuing an alarm output when the phase of the induced voltage of the pair of secondary windings falls below a specified value.

(Function) According to this configuration, when a failure occurs in the differential transformer, the sum of the induced voltages of the pair of secondary windings decreases below the current value, and an alarm output is issued. Failures in dynamic transformers can be detected immediately.

(Embodiment) FIG. 1 is a circuit diagram showing an embodiment of a displacement measuring device according to the present invention.

In the figure, as is well known, a differential transformer 1 has a flexible vJ iron core 1d in between, and one primary winding 1 on both sides.
A and two secondary windings 1b and lc are arranged, and a primary voltage Ep is applied from an AC excitation N source 2 to the primary winding 1a, and each secondary winding 1b.

Each secondary voltage E31. from the IC. ES2 is now induced.

In the case of this differential transformer 1, each secondary winding lb, 1
The secondary voltages ESI and ES2 of c are each independently taken out to the outside, connected to the circuit board 3 via a cable 5, and are harmonically connected within the circuit board 3.

Further, the induced voltage ESIES2 of each of the secondary windings lb and lc is rectified and smoothed independently in the rectifier circuit 3a in the circuit board 3, and then the difference between the two is taken out in the adder circuit 3b and output as a displacement proportional signal. It is output from the circuit board 3 to the outside.

Further, the summed output voltage ES- obtained within the circuit board 3 is introduced into a failure detection circuit 4.

In the failure detection circuit 4, this sum output voltage ES- is rectified and amplified by a rectification amplifier circuit 4a, and then compared with a predetermined reference voltage vrer by a comparator 4b. Switching of the circuit 4C is controlled, whereby an alarm output signal is output from the circuit board 3 to the outside.

Next, the operation of the displacement measuring device having the above configuration will be explained with reference to FIG.

Fig. 2(a) is a circuit diagram for explaining the failure points that may occur in the differential transformer 1, and Fig. 2(b) shows the value of the sum output voltage E3 when the differential transformer is normal. This is a graph showing.

According to the circuit configuration of FIG. 1, each output ES+, Es2 . E
It can be seen that s- has the values shown in FIG. 2 (11), and the summation output voltage ES- always shows a constant value regardless of the displacement X, as shown by the following equation.

ES-=E31 +ES2 =2b-Ep Next, the summation connection voltage ES-
How this changes will be explained in sequence by taking as an example a case where a failure occurs at each point a to "a" in FIG. 2.

First, if all points from a to
--2b-Ep).

On the other hand, if a disconnection occurs at either the primary circuit or the secondary circuit, t=S--O.

Furthermore, when there is a short circuit between a and b and/or when there is a short circuit between c and 1, ES'''-〇 occurs.

Furthermore, when there is a short circuit between c and 6 and when there is a short circuit between /e and yJi, Es==O.

In addition, when C-[1 is short-circuited, "C is Es" = Es
It becomes 2.

Furthermore, when e-1 is short-circuited, Es==Es1.

In this way, the harmonic connection voltage ES- during normal operation is ES-
= 2b -Ep > ES I or Es2〉O, so monitor this ES- and check if ES is 2b-
It is possible to detect that a failure has occurred in the differential transformer 1 by recognizing that the voltage has become equal to or lower than Ep (Vrer).

In this way, according to the embodiment shown in FIG. 1, the secondary side of the differential transformer 1 is connected in a summative manner, so that the normal voltage ES-
is always in the relationship ES' = 2b Ell > ES + or Es2 > O, and at what point in the connection from the differential transformer 1 to the circuit board and the connection line of the AC magnetostatic power supply does a failure (disconnection, short circuit) occur? However, if the summation connection voltage ES- is monitored, the failure can be immediately detected.

Next, another embodiment of the device of the present invention will be described with reference to FIG.

In FIG. 3, the same components as those in the embodiment shown in FIG. 1 are designated by the same reference numerals, and the explanation thereof will be omitted.

In the embodiment shown in FIG. 3(a), the common connection terminal of the pair of secondary windings lb and lc is extended to the receiver side, and an input impedance R is connected to each circuit.

In this case, if a disconnection occurs in any one of c2-C1-d 1-d2, ES-Y ES2 If a disconnection occurs in any of C2-el-fl-12, ES--E! z When both circuits are disconnected, it becomes Es −-0, and the reference voltage V ref of the failure detection circuit 4 and ES'
A failure can be detected by comparing the

Further, at the same time as a failure is detected, the displacement proportional signal is short-circuited to the common by the switch circuit 4C.

In this case, as shown in the figure, the summation connection voltage E
The AC meter relay 6 may be directly driven by S-.

Moreover, FIG. 3(b) shows still another embodiment,
In this example, the induced voltage of each secondary winding ESt Es
After insulating one or both of 2 through the transformer 3C13d, this is subtracted in the adding circuit 3b, thereby obtaining a displacement proportional AC signal.

At this time, the failure detection circuit 4 shown in FIG. 1 may be used as the failure detection circuit.

According to each of the embodiments described above, in this type of displacement measuring device, if a failure occurs in the differential transformer 1, this can be detected and immediately notified to the outside.

J3, in the above embodiment, the induced voltages ESI and ES2 of the pair of secondary windings of the differential transformer 1 are independently taken out to the outside, and they are summatively connected in an alternating current manner to generate the summative output voltage E.
Although S- is determined, rectified, and compared with the reference voltage vrer to obtain an alarm output signal, the present invention is not limited to such a configuration.

For example, while the induced voltages of a pair of secondary windings lb and 1c are differentially connected in an alternating current manner as in the conventional case, each induced voltage ES1. E.S.
2 separately! ii current may be smoothed and converted into direct current, and then both may be added, and the added voltage may be compared with a reference voltage V rcf to obtain an alarm output signal.

[Effects of the Invention] As is clear from the above invention, according to the present invention, a failure such as a disconnection in a differential transformer can be immediately detected in a displacement measuring device using this type of transformer. Become.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of a displacement measuring device according to the present invention.
The circuit diagram, Fig. 2 (a) is a circuit diagram showing each point a to `` where a failure may occur in the circuit configuration of Fig. 1.
Figure (b) shows the summation connection voltage E in the circuit configuration of Figure 1.
Graph for explaining the movement of S-, Figure 3 (a')
1 is a circuit diagram showing another embodiment of the present invention, FIG. 3(b) is a circuit diagram showing another embodiment, and FIG. 4(a) is a circuit diagram showing the configuration of a conventional displacement measuring device. , FIG. 4(b) is a graph showing the operation of the conventional device. 1...Differential transformer ia, ic...pair of secondary windings 4...failure detection circuit

Claims (1)

[Scope of Claims] A displacement measuring device that measures a target displacement amount based on a difference in induced voltage between a pair of secondary windings provided in a differential transformer, comprising: A displacement measuring device characterized in that it is provided with means for emitting an alarm output when the sum decreases below a specified value.