JPH08201412A - Eddy current type current meter - Google Patents

Abstract

PURPOSE: To make possible an eddy current type current meter used for a conductive fluid, such as the molten steel from a continuous casting machine, etc., to accurately measure the flow velocity of the fluid by correcting gap variation. CONSTITUTION: A C-type core 1 is provided near molten steel 9 and an exciting coil 2 and gap variation detecting coil 3 are wound around the core 1 and connected to an AC power source 5 and amplifier 7. A magnetic flux detecting coil 4 is provided at the central part of the core 1 and inputs detecting signals to a correction circuit 8 through a phase rectifying circuit 6. When the coil 2 is excited, a magnetic flux ϕs is generated by an eddy current at each magnetic pole of the molten steel 9 and, as the molten steel 9 moves at a speed (V), a magnetic flux ϕv is generated at the central part of the core 1 owing to the movement of the magnetic flux ϕs . Since the magnetic flux ϕv is measured by means of the magnetic flux detecting coil 4 and the variation caused by the gap variation measured by the gap variation detecting coil 3 is corrected by means of the correction circuit 8, the flow velocity (v) of the molten steel 9 can be measured with accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current anemometer capable of measuring the flow velocity of a conductive fluid such as molten steel in a meniscus in a mold of a continuous casting facility.

[0002]

2. Description of the Related Art A typical example of a conventional eddy current type velocity meter is shown in FIG. In FIG. 4A, the exciting coil 30 is excited by an AC power supply 35, and
One set of two detection coils 32 is arranged so as to be orthogonal to each other, and an eddy current is generated in the metal body 39 moving in close proximity,
The magnetic flux generated by the eddy current generated by the movement of the metal body 39 is differentially connected to the two detection coils 31 and 32, and the amplifier 3
The speed of the metal body 39 which is amplified and moved in 3 is detected.

The operation of the conventional eddy current type anemometer having the structure shown in FIG. 4A will be described. As shown in FIG. 4B, the eddy current i _s ′ is generated in the metal body 39 by the magnetic flux φ generated by the exciting coil 30 (see the dotted line in FIG. 4B). By the magnetic flux φ and the movement of the metal body 39, the metal body 39-
The currents _iv 'and _iv ' flow (see the solid line in FIG. 4B). This current -i _v ', i _v' occurs '-.phi _iv and' flux phi _iv by the detection coil 3 of the differential these flux
It is converted into a voltage by 1, 32, amplified by an amplifier 33, and detected as a speed signal.

FIG. 4C shows the distribution of the eddy current i _s ′ generated by the magnetic flux φ as seen from the side, and FIG. 4D shows the magnetic flux φ.
And the distribution of the current i _v ′ generated by the movement of the metal body 39 as viewed from the side.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the anemometer, as shown in FIG.
Magnetic flux φ generated by this and vortex generated by movement of metal body 39
Current i_sMagnetic flux φ created by _iv′, −φ_iv′ Is almost the same
Therefore, the excitation coil 30 and the detection coils 31 and 32
Is required to be placed on top of each other as shown in FIG.
There is. As a result, from the metal body 39 to the coil 30 or 3
Either one of the coils 1, 32 will be placed apart
Eddy current flows due to excitation or movement of the metal body 39.
The magnetic flux generated as a result decreases according to the distance,
Sufficient sensitivity cannot be obtained. In addition, the coil and the metal body 39
When the gap changes, so does the output.
However, there is a drawback that accurate detection cannot be performed.

When such a conventional eddy current type velocity meter is used for measuring the flow velocity of molten steel on the meniscus of a continuous casting machine (continuous casting machine), the output changes as described above when the meniscus changes. , The accurate flow velocity measurement is not possible.

In order to solve such a problem, the present invention places an exciting coil and a detecting coil close to a conductor to improve electromagnetic coupling with the conductor, and further measures a gap change between the coil and the conductor. The purpose of the present invention is to provide an eddy current type anemometer capable of compensating the output change due to the gap change, and further disposing such an anemometer on the meniscus of the continuous casting machine to measure the molten steel flow velocity. An object of the present invention is also to provide an eddy current type velocity meter which can accurately adjust the current of the electromagnetic brake and can be applied to reliably prevent inclusion of oxides and impurities in the powder.

[0008]

Therefore, according to the present invention, there is provided an eddy current type anemometer comprising a C-shaped core, a coil wound around the C-shaped core, and a magnetic flux detecting coil arranged at the center of the C-shaped coil. And Further, the coil in such an anemometer is composed of a primary coil and a secondary coil, the secondary coil detects the gap fluctuation between the C-shaped core and the conductive fluid, and the value detected by the magnetic flux detection coil. With a means for correcting
Furthermore, the magnetic flux detection coil of such an eddy current type velocity meter is arranged in the meniscus part of the upper part of the mold of the continuous casting machine, and the eddy current that controls the electromagnetic brake of the continuous casting machine by the output of the detected molten steel flow velocity. A velocity meter configuration is also provided.

That is, according to the present invention, (1) a C-shaped core arranged along a flow path of a conductive fluid, a coil wound around the C-shaped core, and a C-shaped core arranged at the center of the C-shaped core. A magnetic flux detecting coil that detects the magnetic flux due to an eddy current generated in the conductive fluid when the conductive fluid moves due to the excitation of the coil, and detects the moving speed of the conductive fluid. An eddy current type velocity meter is provided.

Further, (2) in the above invention (1),
The coil wound around the C-shaped core is composed of a primary coil and a secondary coil, and the primary coil is excited to generate an output due to a change in the gap between the C-shaped core and the conductive fluid generated in the secondary coil. An eddy current type anemometer is provided, which is provided with a means for correcting a magnetic flux detection value detected by the magnetic flux detection coil and reduces an error.

(3) In the invention of (1) or (2) above, the magnetic flux detecting coil measures the molten steel flow velocity in the mold in order to properly supply powder to the mold wall, and the measured value is the same. The eddy current method characterized in that it is arranged on the mold meniscus of a continuous casting machine having a braking force adjusting means for adjusting the braking force of the electromagnetic brake to prevent powder inclusion and is used for measuring the molten steel flow velocity. It also provides a velocity meter.

[0012]

According to the present invention, according to the invention of (1), when the coil wound around the C-shaped core is excited at a predetermined frequency, the conductive fluid adjacent to the C-shaped core is electromagnetically induced. An eddy current flows, and the magnetic flux (φ _s ) at each pole position decreases the magnetic flux (φ) of each magnetic pole due to the current.
Occurs, and the magnetic flux in the opposite direction cancels out in the middle of the C-shaped core, resulting in almost “0”. When the conductive fluid moves in this state, the generated magnetic flux (φ _s ) and an eddy current flow due to the movement, and a magnetic flux (φ _v ) is generated in the middle portion of the C-shaped core.
The magnetic flux (φ _v ) is detected by the magnetic flux detecting coil, and the flow velocity of the conductive fluid is detected from the change in the magnetic flux.

In the invention of (2), the flow velocity of the conductive fluid is detected in the same manner as described above, but the coil is composed of primary and secondary coils, and is excited by the primary coil and the secondary coil is used. The coil detects changes in magnetic flux, and C
When the gap between the mold core and the conductive fluid changes, the magnetic flux (φ _s ) changes, and the output detected by the secondary coil also changes. As the output increases, the magnetic flux (φ _s ) also decreases as the gap increases, and φ-φ _s increases, so that the output of the secondary coil also increases. The output measured by the secondary coil is used to correct the value measured by the magnetic flux detecting coil by the correcting means, so that the velocity of the conductive fluid can be detected with high accuracy.

Further, in the invention of (3), since the eddy current type anemometer is arranged so that the magnetic flux detecting coil detects the flow velocity of the molten steel on the meniscus, the electromagnetic brake is adjusted by its output, and the brake is applied. The flow velocity of the molten steel that is injected from the nozzle by force and flows in the mold can be made an appropriate flow. Therefore, applying such an eddy current type velocity meter to a continuous casting machine, the molten steel flow rate of the continuous casting machine is properly controlled by its output, and the molten steel directly hits the mold wall at the flow rate of the molten steel injected from the nozzle and solidifies. The thickness of the shell is not reduced and the shell is not damaged, and it is possible to reliably prevent insufficient lubrication due to insufficient powder, and to prevent the powder from being wound into a slab.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of an eddy current type velocity meter according to an embodiment of the present invention. The configuration of the figure is shown as a specific configuration example when the molten steel flow velocity on the mold meniscus of the continuous casting machine is measured. In the figure, 1 is a C-shaped core, 2 is an exciting coil, 3 is a gap change detecting coil, 4 is a magnetic flux detecting coil arranged in the central portion of the C-shaped core 1, and 5 is an AC power source for exciting the exciting coil 2. 6 is a phase rectifier circuit, 7 is an amplifier that amplifies the detection signal of the gap detection coil 3, 8 is a correction circuit that inputs and corrects the detection signal of the gap detection coil 3 and the signal from the phase rectification circuit 6,
9 is molten steel.

Next, the operation of the eddy current type anemometer having such a structure will be described with reference to FIG. As shown in FIG. 2A, the excitation coil 2 on the primary side has a frequency of several tens to several tens.
It is excited by 0 MZ AC power supply 5 and at a certain moment, as shown in FIG.
It is assumed that the magnetic flux φ is generated as shown in (a).

The magnetic flux φ causes the molten steel 9 to move to the molten steel 9 shown in FIG.
Eddy current i due to electromagnetic induction_s1, I_s2(Figure
(Indicated by the dotted line), to reduce the magnetic flux φ of each pole.
Towards φ _sOccurs, but as shown in Fig. 2 (c), a C-shaped core
In the middle part of 1, it is canceled by the reverse magnetic flux of the left and right magnetic poles.
Is almost zero.

When the molten steel 9 moves as shown by the flow velocity V as shown in FIG. 2 (b), eddy currents i _v1 and i _v2 (shown by solid _lines ) flow in the molten steel 9, and as shown in FIG. 2 (d). C type core 1
A magnetic flux of φ _v is generated in the middle part of. This magnetic flux φ _v can be efficiently detected by the magnetic flux detecting coil 4 installed close to the molten steel 9.

2 (c) shows the magnetic flux φ.₁-Φ for molten steel 9
Shows the distribution of the eddy current generated in₁
-Eddy current i generated in φ_s1, I_s2, The dotted line synthesizes it
Current i_sIs shown. Fig. 2 (d) shows the magnetic flux φ₁-Φ and molten steel 9
The distribution of the eddy current generated by the movement of
The solid line is the eddy current i_v1, I_v2, The dotted line is the synthetic current i
_vIs shown.

Next, when the gap between the C-shaped core 1 and the molten steel 9 changes due to the change of the molten metal surface, the magnetic flux φ _s shown in FIGS. 2 (b) and 2 (c) changes, which causes the gap change detecting coil 3 to change. Output changes according to the following equation (1).

[0021]

[Equation 1]

In the case of molten steel in the equation (1), as the gap increases, the eddy current i _s flowing in the molten steel 9 decreases, so φ _s also decreases, φ-φ _s increases, and the output generated in the secondary coil 3 becomes To increase. The output of the magnetic flux detecting coil 4 is as shown in the following equation (2).

[0023]

[Equation 2]

When the gap changes in the equation (2),
From B = φ / S, the magnetic flux density B can be calculated from the equation (1) to the following (3)
It looks like an expression.

[0025]

(Equation 3)

Therefore, the change in the magnetic flux density B due to the change in the gap is corrected by the correction circuit 8 composed of a multiplication circuit ((3)
By substituting B obtained by the equation into B of the equation (2)), the change in the output V _d of the magnetic flux detecting coil 4 due to the gap change is corrected, and the speed of the molten steel 9 can be accurately detected.

FIG. 3 is a diagram showing a configuration in which the eddy current type velocity meter having the above-mentioned configuration is arranged on the meniscus of the continuous casting machine. This figure shows an example in which the molten steel velocity on the meniscus is detected by an eddy current anemometer and applied to the current control of an electromagnetic brake. In the figure, 100 and 101 are molten steel velocity detectors corresponding to the magnetic flux detection coil of FIG. 1, 102 is a brake current adjusting device, 1
03 is an electromagnetic brake, 104 is a nozzle, 105 is powder, 106 is molten steel, 107 and 108 are mold walls, 10
9, 110 is a solidification shell.

In such a structure, the molten steel 106 injected from the nozzle 104 is supplied into the mold, and its flow flows as shown by the solid line 120 in FIG.
By directly hitting 7, 108, a flow can be made toward the upper and lower parts of the mold. The solidified shells 109, 110 are washed with the flow of directly hitting the mold walls 107, 108, and the discharge flow of the nozzle 104 is controlled by the electromagnetic brake 102 in order to prevent breakout or the like due to a decrease in the thickness of the solidified shell.

When the discharge flow is braked or the braking force is increased, the molten steel flow toward the meniscus is reduced. When the molten steel flowing toward the meniscus decreases, the molten steel temperature of the meniscus lowers, the melting of the powder 105 becomes insufficient, the lubrication with the mold walls 107 and 108 becomes insufficient, and the surface properties of the slab are adversely affected.

When the braking force is weakened, the molten steel directed to the meniscus increases, the melting of the powder is promoted as the temperature of the molten steel rises, and the swirl flow increases, and the powder 1 in the slab 1 increases.
A problem that 05 is involved occurs.

Therefore, the molten steel flow velocity detectors 100 and 101 detect the flow velocity on the meniscus, and the brake current adjusting device 10 is detected.
By adjusting the brake current in step 2 to optimize the flow of molten steel on the meniscus, it becomes possible to produce a slab with good quality.

By applying the eddy current type speed meter to the continuous casting machine as described above, even if the molten steel flow on the meniscus changes due to a change in the discharge flow due to melting damage or clogging of the nozzle 104, the molten steel flow velocity By detecting the flow velocity with the detectors 100 and 101 and controlling the braking force of the electromagnetic brake 103, the powder 105 can be appropriately supplied, so that the quality can be improved.

[0033]

As described above in detail, the present invention provides an eddy current including a C-type core, a coil wound around the C-type core, and a magnetic flux detecting coil arranged in the center of the C-type coil. The configuration of a current meter. In addition, the coil in such an anemometer is composed of a primary coil and a secondary coil, and the secondary coil detects the gap variation between the C-shaped core and the conductive fluid, and the value detected by the magnetic flux detecting coil is A configuration provided with a means for correcting, further, the magnetic flux detection coil of such an eddy current type velocity meter is arranged in the meniscus portion of the mold upper part of the continuous casting machine,
Since the configuration of the eddy current type velocity meter which controls the electromagnetic brake of the continuous casting machine by the output of the detected molten steel flow velocity is also provided, the following effects are achieved.

(1) By using the C-type core, the magnetic flux density on the surface of the conductive fluid can be increased and a large eddy current can be passed through the conductor.

(2) By using the C-type core, the magnetic flux generated by the movement of the conductive fluid becomes maximum in the middle part of the C-type core, and a large output can be obtained by installing the magnetic flux detecting coil in this part. .

(3) The flow velocity can be accurately measured by detecting the gap change of the C-shaped core by the secondary coil for detecting the gap change and correcting the measured value.

(4) The entrainment of powder can be predicted by detecting the molten steel flow on the meniscus in the continuous casting machine, and the powder lubrication can be optimized and entrainment can be prevented by adjusting the braking force of the electromagnetic brake. The quality of the cast pieces in the vertical casting machine is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an eddy current type velocity meter according to an embodiment of the present invention.

2A and 2B are explanatory views of the operation of an eddy current type anemometer according to an embodiment of the present invention, in which FIG. 2A shows the structure of a detection unit, and FIG. Occurrence state, (c)
Shows the waveform and magnetic flux of the eddy current, and (d) shows the waveform and magnetic flux of the current generated by the movement of the molten steel.

FIG. 3 is a configuration diagram when an eddy current type velocity meter is arranged on a meniscus of a continuous casting machine according to an embodiment of the present invention.

4A and 4B are explanatory views of the configuration and action of a conventional eddy current type velocity meter, where FIG. 4A shows the configuration of the velocity meter, and FIG. 4B shows the current generated by electromagnetic induction, the magnetic flux, and the movement of the metal body. The states of current and magnetic flux are shown in (c), the waveform of the current generated by electromagnetic induction and the magnetic flux, and (d), the waveform of the current generated by the movement of the metal body and the magnetic flux.

[Explanation of symbols]

 1 C-type core 2 Excitation coil 3 Gap change detection coil 4 Magnetic flux detection coil 5 AC power supply 6 Phase rectification circuit 7 Amplifier 8 Correction circuit 9 Molten steel 100, 101 Molten steel speed detector 102 Brake current regulator 103 Electromagnetic brake 104 Nozzle 105 Powder 106 Molten steel 107,108 Mold wall 109,110 Solidified shell

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Motoki Nakajima 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute

Claims (3)

[Claims] 1. A C arranged along a flow path of a conductive fluid.
A core wound around the C-shaped core and a coil wound around the C-shaped core, the coil is excited at the center of the C-shaped core, the conductive fluid moves, and the eddy current is generated in the fluid. An eddy current type anemometer, comprising: a magnetic flux detecting coil for detecting a magnetic flux, and detecting a moving speed of the conductive fluid. 2. The coil wound around the C-shaped core is composed of a primary coil and a secondary coil, and the primary coil is excited so that the coil between the C-shaped core and the conductive fluid is generated in the secondary coil. 2. The eddy current type velocity meter according to claim 1, further comprising means for correcting a magnetic flux detection value detected by the magnetic flux detection coil by an output due to a gap change, thereby reducing an error. 3. The magnetic flux detecting coil measures the molten steel flow velocity in the mold in order to properly supply the powder to the mold wall, and adjusts the braking force of the electromagnetic brake with the measured value to prevent the powder from being caught. The eddy current type anemometer according to claim 1 or 2, wherein the eddy current type anemometer is arranged on a mold meniscus of a continuous casting machine having a braking force adjusting means, and used for measuring the molten steel flow velocity.