JPH09210608A - Inductance type displacement measurement circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability by so changing a path that d.c. voltage signal- outputted from a rectification circuit is outputted through a correction circuit when a rotation number to be measured reaches specified value, for correcting deterioration of sensitivity caused by reduction of impedance due to main magnetic flux from a displacement gage. SOLUTION: When the number of rotation of a turbine rotor 2 increases and reaches the rated speed, a correction path is selected through a comparator 29 and switches 27 and 26. That is, the output from a zero-span adjustment circuit 15 passes amplifiers 22 and 25 of a zero-spart adjustment circuit 21 and, through the switch 26, introduced to an output terminal 1. A circuit constant of the path (correction path) is set at a value which corrects deterioration of displacement gage sensitivity due to a virtual secondary circuit 16 at increasing of number of rotation. Thus, with the adjustment circuit 21, sensitivity deteriorated-amount caused in such a way that the virtual secondary circuit 16 formed in the rotor 2 reduces impedance caused by main flux of displacement gages 10A and 10B is corrected, so that difference of extension is measured with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential expansion meter used as one of turbine monitoring instruments, and more particularly to detecting expansion of a turbine casing or turbine rotor when a turbine is rotating at a high speed. The present invention relates to an inductance type displacement measuring circuit.

[0002]

2. Description of the Related Art Turbine generators generate electric power by rotating a turbine at high speed with steam to rotate a generator connected to the turbine. As shown in FIG. 6, in a general turbine generator, power generation connected to the turbine rotor 2 by introducing high-temperature steam into the turbine rotor 2 arranged in the passenger compartment 1 and rotating the turbine rotor 2 is performed. Rotate machine 3. Therefore, in order to increase the power generation efficiency of the turbine, the blades 4 provided on the turbine rotor 2 and the ground portion of the turbine casing 1 are installed so that the distance between them is very narrow. .

On the other hand, when high temperature steam is applied to the turbine,
The turbine casing 1 and the turbine rotor 2 are expanded due to the temperature of the steam and the centrifugal force of the turbine rotation. However, since the expansion is not uniform, the expansion is measured by a moving amount measuring and monitoring system using an inductance type displacement gauge 5. The difference is measured and monitored so that the blade 4 and the ground portion do not come into contact with each other.

FIG. 5 shows an example of the configuration of an inductance type differential expansion meter used in a moving amount measuring and monitoring system of a turbine generator. In this inductance type differential expansion meter, displacement gauges 10A and 10B are arranged close to a turbine rotor 2 (both side surfaces of a flange portion 2'formed on the outer periphery thereof), and an excitation AC power supply 11 is connected to the displacement gauges 10A and 10B. doing. Displacement gauges 10A, 10B using an AC power supply 11 for excitation
The signal output from the AC bridge circuit 12 is extracted. The synchronous rectification circuit 14 driven by the AC power supply 13 for synchronous rectification detects the difference between the output signals of the displacement gauges 10A and 10B, and detects the signal proportional to the expansion difference. This signal is adjusted by the zero-span adjusting circuit 15 to a voltage corresponding to the full scale of the differential expansion measurement range and a voltage corresponding to zero of the differential expansion measurement so that the predetermined signal is obtained at the full scale of the differential expansion measurement range. Is adjusted to.

By the way, since the displacement gauges 10A and 10B are excited by the power supply frequency voltage, a virtual secondary circuit 16 is formed in the turbine rotor 2 as shown in FIG. The virtual secondary circuit 16 formed in the turbine rotor 2 acts to reduce the impedance due to the main magnetic flux applied from the displacement gauges 10A and 10B. However, the action of reducing the main magnetic flux from the displacement gauge increases as the rotational speed of the turbine rotor 2 increases, and acts to cancel the output voltage corresponding to the detected elongation difference.

Therefore, when the rotation speed is small, the output voltage of the differential expansion meter becomes a value proportional to the distance, but when the rotation speed is large, the output voltage of the displacement meter becomes smaller than the voltage proportional to the distance, resulting in a large measurement error. Become.

[0007]

As described above, in the conventional inductance type differential expansion meter, the output voltage of the displacement gauge becomes smaller than the voltage proportional to the actual distance when the rotational speed of the turbine rotor becomes high, and the measurement is made. There is a problem that the error becomes large.

The present invention has been made in view of the above situation, and corrects a decrease in sensitivity due to a decrease in impedance due to the main magnetic flux from the displacement meter when the rotational speed of the turbine rotor increases. It is an object of the present invention to provide an inductance type displacement measuring circuit which can be realized and has high reliability.

[0009]

In order to achieve the above object, the present invention takes the following measures. The present invention corresponding to claim 1 has an exciting AC power supply that generates an exciting AC voltage, and a pair of coils whose inductance changes according to the amount of movement of the measurement target. A displacement meter that outputs an electric signal corresponding to the inductance of the coil and a bridge circuit that captures the electric signal output from the displacement meter and detects the differential voltage of the electric signal that has flowed to each coil, A rectifier circuit that generates a DC voltage signal from a differential voltage detected by a bridge circuit, and an input / output characteristic that corrects a change in output characteristic of the displacement meter due to rotation of the measurement target and a decrease in main magnetic flux of the displacement meter. And a DC voltage signal output from the rectifier circuit is output via the correction circuit when the rotation speed signal of the measurement target reaches a predetermined rotation speed. And a path selection means for switching the path.

According to the inductance type displacement measuring circuit of the present invention, an electric signal corresponding to the inductance of the coil is output from the displacement gauge, the differential voltage of the electric signal flowing through each coil is detected in the bridge circuit, and the rectifying circuit is further provided. At, the differential voltage detected by the bridge circuit is converted into a DC voltage signal and output. Then, when the rotation speed signal of the measurement target reaches a predetermined rotation speed, the path is switched by the path selecting means so that the DC voltage signal output from the rectifier circuit is output via the correction circuit. Since the input / output characteristics are set in the correction circuit to correct the change in the output characteristics of the displacement meter due to the rotation of the measurement target and the decrease in the main magnetic flux of the displacement meter, the impedance is reduced by the virtual secondary circuit. The correction circuit outputs a differential expansion signal that has been subjected to sensitivity correction corresponding to the amount of sensitivity reduction.

According to a second aspect of the present invention, there is provided an exciting AC power supply for generating an exciting AC voltage, and a pair of coils whose inductance changes according to a moving amount of a measurement target. A displacement meter to which an alternating voltage is applied from which an electric signal corresponding to the inductance of the coil is output, and a bridge circuit which receives the electric signal output from the displacement meter and detects a differential voltage of the electric signal flowing to each coil. And a rectifier circuit that generates a DC voltage signal from the differential voltage detected by this bridge circuit, and a DC voltage signal output from this rectifier circuit, respectively, is input, and the measurement target rotates and the main magnetic flux of the displacement meter changes. Input / output characteristics that correct the output characteristic change of the displacement gauge due to decrease, and input / output characteristics corresponding to each of multiple rotational speeds are set separately. Comprising the, and selection means speed based on the speed signal to select the output of the corresponding correction circuit upon reaching a speed corresponding to the input-output characteristics set to the correction circuit.

According to the inductance type displacement measuring circuit of the present invention, when the rotational speed signal reaches the rotational speed corresponding to the input / output characteristic set in the correcting circuit, the output of the corresponding correcting circuit is selected by the selecting means. , The input / output characteristic of the correction circuit can be sequentially switched to a suitable characteristic for each rotational speed from 0 to a high rotational speed, and a highly reliable measured value can be always obtained.

According to a third aspect of the present invention, in the inductance type displacement measuring circuit according to the first aspect or the second aspect, the rotation output from the rotation number detector measuring the rotation number of the measurement target is output. A rotation speed measuring circuit for converting the speed detection signal into a rotation speed signal of a signal matched with the path selecting means is provided.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. (First Embodiment) FIG. 1 shows a first embodiment in which the present invention is applied to an inductance type differential expansion meter used in a moving amount measuring and monitoring system of a turbine generator. In addition,
The same parts as those of the inductance type differential expansion meter shown in FIG. 5 described above are denoted by the same reference numerals.

In this inductance type differential expansion meter, a pair of displacement gauges 10A and 10B are arranged close to the turbine rotor 2, and an exciting AC power source 11 is connected to the displacement gauges 10A and 10B for excitation. The differential expansion signal output from the displacement gauges 10A and 10B is taken out by the AC bridge circuit 12, and the difference is detected by the synchronous rectification circuit 14 driven by the synchronous rectification AC power supply 13, and a signal proportional to the differential expansion is first detected. To the zero-span adjustment circuit 15 of. The first zero-span adjustment circuit 15 adjusts the voltage corresponding to the full scale of the differential expansion measurement range and the voltage corresponding to zero of the differential expansion measurement, and a predetermined unified signal ( For example, 1 to 5 VDC). The differential expansion signal thus adjusted is input to the second zero-span adjusting circuit 21.

The second zero-span adjustment circuit 21 has a first
Amplifier 22 and variable resistor 23 for adjusting the zero point
And a feedback resistor 24 for adjusting the gain and a second amplifier 25. The output of the second amplifier 25 is the first
It is sent to the output terminal T1 via the switch 26. First
The path from the input stage of the amplifier 22 to the output terminal T1 via the second amplifier 25 and the first switch 26 (hereinafter,
The circuit constant of the "correction path") is set to a value that corrects the decrease in the sensitivity of the displacement meter due to the virtual secondary circuit 16 when the rotation speed increases. Specifically, FIG.
Set the circuit constants that give the input / output characteristics shown in.

The input stage of the second zero-span adjusting circuit 21 is connected to the output terminal T1 by the second switch 27.
Are directly connected via. 2 (a) shows the input / output characteristics of the path from the input stage of the second zero-span adjusting circuit 21 to the output terminal T1 via the second switch 27 (hereinafter referred to as "non-correction path"). The characteristics are set as shown in.

On the other hand, a rotation speed signal supplied from a device measuring the rotation speed of the turbine rotor 2 is applied to one input terminal of the comparator 28. A voltage corresponding to the rated rotation speed (high rotation speed) is applied to the other input terminal of the comparator 28. The comparator 28 is set to change from high level to low level when the rotation speed reaches the rated rotation speed. The output stage of the comparator 28 is directly connected to the second switch 27, and the inverter 3 is connected to the first switch 26.
Connected through 0. The first and second switches 26 and 27 are closed when the switch inputs are at high level.

In the inductance type differential expansion meter constructed as described above, when the rotational speed of the turbine rotor 2 is less than the rated rotational speed, the output of the comparator 29 is at a high level, so the second switch 27 is closed. Then, the first switch 26 is opened and the non-correction path is selected. That is, a path is formed in which the output of the first zero-span adjustment circuit 15 is directly guided to the output terminal T1 via the second switch 27.

When excited by the exciting AC power supply 11, a current corresponding to the inductance of the coils of the displacement gauges 10A, 10B flows and is taken out by the AC bridge circuit 12, and the difference is detected by the synchronous rectification circuit 14, and the expansion difference is detected. A signal proportional to is input to the first zero-span adjustment circuit 15. The signal adjusted by the first zero-span adjusting circuit 15 is input to the second zero-span adjusting circuit 15,
The signal is output as it is from the output terminal T1 to the outside through the second switch 27 without being corrected by the amplifier 22 of FIG.

Since the rotational speed is now low, the impedance reduction due to the virtual secondary circuit 16 formed in the turbine rotor 2 is extremely small. Therefore, even if the signal adjusted by the first zero-span adjustment circuit 15 is directly output to the outside via the second switch 27, the measurement error can be ignored.

When the rotation speed of the turbine rotor 2 rises to reach the rated rotation speed, the output of the comparator 29 changes from high level to low level, the second switch 27 opens and the first switch 26 closes. Then, the correction path is selected. That is, the first zero-span adjustment circuit 1
A path is formed in which the output of 5 passes through the first and second amplifiers 22 and 25 and is led to the output terminal T1 via the first switch 26.

At this time, in the turbine rotor 2, since the impedance due to the main magnetic flux from the displacement gauge is reduced by the virtual secondary circuit 16, the displacement gauge sensitivity is lowered. The expansion difference signal acquired when the sensitivity is decreased in accordance with the decrease in impedance is adjusted by the first zero-span adjustment circuit 15 and further input to the second zero-span adjustment circuit 21.

The second zero-span adjusting circuit 21 is shown in FIG.
As shown in (b), a correction path having an input / output characteristic for correcting the sensitivity deterioration of the displacement gauge has first and second switches 26, 27.
The differential expansion signal input to the second zero-span adjusting circuit 21 is selected by the first and second amplifiers 2.
When passing through 2, 25, etc., the displacement reduction of the displacement gauge is corrected by signal conversion according to the input / output characteristics shown in FIG. The differential expansion signal thus corrected is output terminal T1.
Is output to the outside.

As described above, according to this embodiment, when the rotational speed increases to the rated rotational speed, the second zero-span adjusting circuit 21 causes the virtual secondary circuit formed in the turbine rotor 2 to operate. Since 16 compensates for the decrease in sensitivity due to the decrease in impedance due to the main magnetic flux from the displacement gauge, even if the rotational speed of the turbine rotor 2 increases and the rated rotation is entered, a highly accurate expansion difference is obtained. A measurement can be made.

(Second Embodiment) FIG. 3 shows the configuration of an inductance type differential expansion meter according to the second embodiment.
The inductance type differential expansion meter of the present embodiment has the same configuration as that of the first embodiment except that the rotation speed measurement circuit 30 is incorporated. The same parts as those of the inductance type differential expansion meter shown in FIG. 1 are designated by the same reference numerals.

This inductance type differential expansion meter operates by inputting the rotation speed pulse signal output from the rotation speed detector 31 into the rotation speed measurement circuit 30, converting it into a rotation speed voltage signal, and inputting it to the comparator 28. I am letting you. And comparator 2
The output of 8 selects the path of the second zero-span adjusting circuit 21.

(Third Embodiment) FIG. 4 shows the configuration of an inductance type differential expansion meter according to the third embodiment.
The same parts as those of the inductance type differential expansion meter of the first embodiment shown in FIG. 1 are designated by the same reference numerals.

In the inductance type differential expansion meter of this embodiment, a plurality of second zero-span adjusting circuits 21-1 to 21- having different input / output characteristics are provided at the output stage of the first zero-span adjusting circuit 15. n are connected in parallel. These second
The output of the zero-span adjustment circuits 21-1 to 21-n and the output of the first zero-span adjustment circuit 15 of the selection circuit 35.
Configure to select with. On the other hand, different comparator levels are set to the plurality of comparators 28-1 to 28-n to which the respective rotation speed signals are input, so that the outputs of the comparators 28-1 to 28-n change at different rotation speeds. I have to. The selection circuit 35 includes these comparators 28-1 to 28-.
Based on the output of n, the output of the corresponding second zero-span adjusting circuits 21-1 to 21-n or the output of the first zero-span adjusting circuit 15 is selected and sent to the output terminal T1.

According to the present embodiment as described above, the comparator levels corresponding to a plurality of rotation speeds from 0 to the rated rotation speed are set in stages in the plurality of comparators 28-1 to 28-n. As a result, the rotational speed of the turbine rotor 2 up to the rated rotational speed can be detected in stages.
Then, a plurality of second zero-span adjustment circuits 21-1 to 21-n having suitable input / output characteristics for each rotation speed are provided.
The output of the second zero-span adjustment circuit for which the suitable input / output characteristics corresponding to the number of revolutions are set by the selection circuit 35 is set to a value different from that of the first embodiment. It can be finely corrected. The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0031]

As described in detail above, according to the present invention, when the rotation speed of the turbine rotor becomes high, it is possible to correct the sensitivity decrease due to the decrease of the impedance due to the main magnetic flux from the displacement gauge. It is possible to provide a highly reliable inductance type displacement measuring circuit.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inductance type differential expansion meter according to a first embodiment of the present invention.

FIG. 2 is a diagram showing input / output characteristics of a second zero-span adjustment circuit according to the first embodiment.

FIG. 3 is a configuration diagram of an inductance type differential expansion meter according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of an inductance type differential expansion meter according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional inductance type differential expansion meter.

FIG. 6 is a schematic diagram of a turbine generator including an inductance type differential expansion meter.

[Explanation of symbols]

2 ... Turbine rotor, 10A, 10B ... Displacement meter, 11 ...
AC power supply for excitation, 12 ... AC bridge circuit, 13 ... AC power supply for synchronous rectification, 14 ... Synchronous rectification circuit, 15 ... First zero-span adjustment circuit, 21 ... Second zero-span adjustment circuit, 26 ... 1 switch, 27 ... second switch, 2
8 ... Comparator.

Claims (3)

[Claims] 1. An excitation AC power supply for generating an AC voltage for excitation, and a pair of coils whose inductance changes according to the amount of movement of a measurement target. The AC voltage is applied from the excitation AC power supply to the coil. , A bridge circuit that outputs an electric signal according to the inductance, a bridge circuit that takes in the electric signal output from the displacement meter, and detects the voltage difference between the electric signals that flowed through the coils, and the bridge circuit detects the difference voltage. A rectifier circuit that generates a DC voltage signal from a differential voltage, and a correction that sets an input / output characteristic that corrects a change in the output characteristic of the displacement meter due to the rotation of the measurement target and a decrease in the main magnetic flux of the displacement meter. Circuit and the path is switched so that the DC voltage signal output from the rectification circuit is output via the correction circuit when the rotation speed signal of the measurement target reaches a predetermined rotation speed. An inductance-type displacement measuring circuit, comprising: 2. An exciting AC power supply that generates an exciting AC voltage, and a pair of coils whose inductance changes according to the amount of movement of the measurement target. The AC voltage is applied from the exciting AC power supply to the coil. , A bridge circuit that outputs an electric signal according to the inductance, a bridge circuit that takes in the electric signal output from the displacement meter, and detects the voltage difference between the electric signals that flowed through the coils, and the bridge circuit detects the difference voltage. A rectifier circuit that generates a DC voltage signal from the differential voltage, and a DC voltage signal that is output from this rectifier circuit are respectively input, and the output of the displacement meter due to rotation of the measurement target and reduction of the main magnetic flux of the displacement meter A plurality of correction circuits having input / output characteristics for correcting characteristic changes and having input / output characteristics corresponding to a plurality of rotation speeds separately set, and a rotation circuit based on the rotation speed signal. An inductance type displacement measuring circuit, comprising: a selecting means for selecting an output of a corresponding correction circuit when the number of rotations reaches a rotation number corresponding to an input / output characteristic set in the correction circuit. 3. The inductance type displacement measuring circuit according to claim 1 or 2, wherein the rotation speed detection signal output from a rotation speed detector measuring the rotation speed of the measurement target is used as the route selecting means. An inductance-type displacement measuring circuit, which is provided with a rotation speed measuring circuit for converting a signal corresponding to the above into a rotation speed signal.