JPH0434802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a superconducting coil that can obtain a strong magnetic field without loss.

[Technical background of the invention]

Superconducting coils are generally cooled with liquid helium at minus 269 degrees Celsius and one atmosphere of pressure, so that their electrical resistance becomes zero and they become superconducting. This superconducting coil has an advantage over a general normal conducting coil (the same applies hereinafter) in that there is no power loss and a strong magnetic field can be obtained in a small amount.

However, there is a problem in that a superconducting coil in a superconducting state changes to normal conductivity due to heat generation due to a sudden change in current, frictional heat due to movement of a superconducting conductor, etc., and may even quench in some cases. The occurrence of this quench causes a huge power loss in the superconducting coil, and the superconducting conductor constituting the superconducting coil is heated, causing failures such as burnout and dielectric breakdown of the superconducting coil.

To prevent this, there is a method to protect the superconducting coil by detecting the quench as soon as possible, immediately cutting off the power, and consuming the energy stored in the superconducting coil through an externally connected discharge resistor. is commonly practiced.

Quench detection of the superconducting coil is performed by measuring the terminal voltage of the superconducting coil. That is, when the superconducting coil transitions to normal conductivity, electrical resistance occurs, and this electrical resistance and the current in the superconducting coil generate a voltage, and this voltage is measured to perform quench detection. However, since the superconducting coil has a large inductance, in addition to the voltage generated by the electrical resistance, a voltage is also generated due to current changes and inductance during excitation and demagnetization of the superconducting coil.

In conventional quench detection, a bridge circuit is connected to the midpoint and both terminals of a superconducting coil, thereby removing the voltage generated by the inductance of the superconducting coil, and detecting the voltage due to the electrical resistance of the superconducting coil.

Figure 1 shows a circuit diagram of a conventional superconducting coil.
A bridge circuit 3 is connected to the superconducting coil 1,
As a result, the voltage generated due to the inductance of the coil 1 is removed, and only the voltage generated due to the resistance change of the coil 1 is output. When the voltage obtained by the bridge circuit 3 exceeds a certain set value, the abnormal voltage detection device 4 outputs a failure signal. This output activates the shield breaker 5 to immediately cut off the current. When this shingle 5 breaks, the superconducting coil 1 is configured to consume energy stored in the superconducting coil 1 by a discharge resistor 6 to protect it. Note that 2 is a DC power supply device that excites the superconducting coil 1.

Bridge circuit 3 has two ends of superconducting coil 1 at point A,
Since the point C and the neutral point B are connected and balanced, the difference between the voltage from one end of the superconducting coil 1 to point A to the neutral point B, and from the neutral point B to the other end point C. voltage can be obtained. The voltage due to inductance is uniformly generated in the superconducting coil 1, and A
The voltage from point B to point B is equal to the voltage from point B to point C, and no output is generated. On the other hand, in the case of quenching, a voltage is generated only in the quenched portion, and the balance of the bridge circuit 3 is disrupted, resulting in an abnormal voltage.

Figure 2 is a cross-sectional view of a conventional superconducting coil.
7 is a superconducting coil, 8 is its superconducting conductor, and 9 is a voltage measurement line connected to both terminals of the superconducting coil 7 at point A, point C, and neutral point B.

This voltage measurement line 9 has an inductance due to the area of the shaded portions D and E due to the structure of the superconducting coil. If the areas of the shaded portions D and E are not equal, or if non-uniform magnetic flux due to disturbance interlinks, a noise voltage will occur in the voltage measurement line. Particularly in the case of a pulsed magnet that operates in a pulsed manner, a large noise voltage is generated because changes in magnetic flux generated from an external power supply line, power supply, etc. also change as rapidly as the current of the pulsed magnet. Since the abnormal voltage of the superconducting coil is a weak voltage of about several mV, when such a noise voltage occurs, it becomes difficult to detect the quench of the superconducting coil.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a superconducting coil that can improve the above-mentioned drawbacks of the prior art, reduce the noise voltage generated in the voltage detection line of the superconducting coil, and accurately detect quench.

[Structure of the invention]

To achieve the above object, the present invention uses a support material around which a plurality of superconducting wires are wound as a detection wire, and is equipped with a device for detecting the difference in voltage between the detection wire and the superconducting coil.

[Embodiments of the invention]

An embodiment in which the present invention is applied to a pulse magnet will be described below with reference to FIGS. 3 and 4.

FIG. 3 is an external perspective view of a superconducting conductor for a pulsed magnet, where 10 is a superconducting wire and 11 is a support member that supports the electromagnetic force acting on the superconducting wire 10. In this way, the superconducting conductor 8 in this embodiment has a structure in which a plurality of superconducting wires 10 are wound around the supporting material 11 made of a long conductor. The support material 11 is generally made of stainless steel, and its surface is coated with an insulating coating to insulate it from the superconducting wire 10 and used as a detection wire.

FIG. 4 is a circuit diagram, and the same parts as in FIG. 1 are given the same reference numerals.

Reference numeral 12 denotes a superconducting coil, which is a portion consisting of the superconducting wire 10 shown in FIG. Further, 13 is a detection winding, which is a part made of the support member 11 shown in FIG.

One end of the detection winding 13 is connected to one end of the superconducting coil 12 at point E, and the detection winding 13 and the superconducting coil 1
The other ends of point F and point G of 2 are connected to an abnormal voltage detection device 4.

In the above configuration, since the detection winding 13 is wound together with the superconducting coil 12, it is wound the same number of times in the same part as the superconducting coil 12. Therefore, the magnetic flux of the superconducting coil 12 and the magnetic flux of the detection winding 13 are equal, and since the shapes of the coils are the same, the inductance is also equal. Superconducting coil 1
2 generates voltage at points E and G due to current changes and inductance during excitation and demagnetization. However, the detection winding 13 also generates the same voltage at points E and F. Therefore, the detection winding 13 and the superconducting coil 1
When both ends of 2 are connected at point E, the detection winding 1
3 and the same voltage of the superconducting coil 12 are erased, and no voltage is generated at points F and G.

On the other hand, when the superconducting coil 12 is quenched,
The voltage due to the current and resistance of the superconducting coil 12 is E
It occurs at point G. However, since no current flows through the detection winding 13, this voltage is not generated. Therefore, a difference is created between the voltages of the superconducting coil 12 and the detection winding 13, and voltages are generated at points F and G due to the current and resistance of the superconducting coil 12. This point F and G
A superconducting coil quench is detected by connecting a measurement line to the point and connecting it to the abnormal voltage detection device 4.

In addition, the measurement wires are connected to points F and G at one end of the superconducting coil, and the distance between the superconducting conductor and the detection winding within the superconducting coil is also shortened, reducing the area where magnetic flux interlinks. , it is possible to reduce noise voltage due to magnetic flux changes from disturbances.

As described above, in this embodiment, since the support material disposed at the center of the conductor is used as the detection line, the amount of disturbance between the conductor and the detection line is approximately equal, and malfunctions are reduced.

[Modified example of the invention]

Next, another embodiment will be described.

In the embodiment shown in FIG. 5, both ends of the detection winding 13 are connected at both ends of the superconducting coil 12 at points H and I,
The central cut point K and L point and the neutral point J of the superconducting coil 12 are both connected to the bridge circuit 3. As a result, the area created by the voltage measurement line can be reduced, and noise voltage can be reduced.

Still other embodiments are shown in FIGS. 6 and 7. In this embodiment, the support material 11 shown in FIG.
They are set as 14 and 15 as a pair. In the circuit diagram shown in FIG. 7, reference numerals 16 and 17 indicate detection windings made up of the supporting materials 14 and 15, the detection winding 16 being located at one end of the superconducting coil 12 at point M, and the detection winding 17 being located at a point M at one end of the superconducting coil 12. are connected at the center N point. The bridge circuit 3 is connected to one end O of the superconducting coil 12.
It is connected to point, P point, and Q point. With this configuration, the area due to the connection lines can be reduced and noise voltage can be reduced.

〔Effect of the invention〕

As explained above, in the present invention, since the superconducting wire surrounds the detection wire, the area surrounding the magnetic flux can be reduced, the generated noise voltage can be reduced, and abnormalities in the superconducting coil can be accurately detected. I can do it.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional superconducting coil, Fig. 2 is a sectional view of a conventional superconducting coil, Fig. 3 is an external perspective view of a superconducting conductor used in a superconducting coil according to an embodiment of the present invention, and Fig. 4 5 is a circuit diagram of a superconducting coil showing one embodiment of the present invention, FIG. 5 is a circuit diagram showing another embodiment, FIG. 6 is a perspective view of a superconducting conductor showing still another embodiment, and FIG. This is a superconducting coil using the superconducting conductor shown in FIG. 1, 7, 12...Superconducting coil, 2...DC power supply device, 3...Bridge, 4...Abnormal voltage detection device, 5...Shield breaker, 6...Discharge resistor, 8...Superconducting conductor, 9... Voltage measurement wire, 10... Superconducting wire, 11, 14, 15... Support material, 13, 16,
17...Detection winding.

Claims (1)

[Claims] 1. Detecting the voltage difference between a superconducting coil formed by winding a superconducting conductor made by winding a plurality of superconducting wires around a supporting material, a detection winding formed by the supporting material, and the superconducting coil. A superconducting coil equipped with a device.