JPH01129765A - Superconducting rotor - Google Patents

Abstract

PURPOSE:To sufficiently utilize cooling medium of a current lead by folding a current lead a plurality of times in the axial direction in a vacuum heat insulating space in a torque tube. CONSTITUTION:A first stage current lead 1a made of a normal conducting conductor is connected at its end to a superconducting field winding 5, and temporarily connected at its joint shaft 7 side to a first connection pipe 8a having a U-shaped hole. A folding-second stage current lead 1b is connected to the pipe 8a. A second connection pipe 8b having a U-shaped hole is connected to the other end of the lead 1b, folded to a second stage pipe 8b, and connected with a third stage current lead 1c. The leads 1a-1c are folded in a torque tube 6 and a vacuum heat insulating space 9 in the torque tube 6 surrounded by the end faces of a low temperature rotor 3 and the shaft 7. The folded opposite end of the lead 1c is connected through the shaft 7 to a collector ring 10 by a connection conductor 10.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a superconducting rotor for a rotating electric machine.

(Prior Art) Recently, a generator equipped with a so-called superconducting rotor that uses a superconducting conductor as a rotating field winding has been developed. Field windings using superconducting conductors must be cooled to below a critical temperature in order to maintain their superconductivity.1For example, if NbTi, Nb, or Sn is used as the conductor, the cooling medium must be cooled to about 4. liquid helium.

Such low-temperature refrigerants generally have a small latent heat of vaporization and are easily vaporized. Therefore, in order to maintain the superconducting state of the superconducting field windings, it is necessary to minimize the heat intruding into the low-temperature rotor equipped with the field windings. need to be reduced.

Invasive heat is classified into radiant heat transfer, lean gas heat transfer, conductive heat transfer, etc., but in order to suppress these, conventionally, a vacuum layer with low vacuum pressure was created around the low-temperature rotor, and mechanically the low-temperature rotor was separated from the room temperature rotor. The structural members connecting the rotors were cooled by a gaseous refrigerant vaporized within the low temperature rotor. In other words, the refrigerant is not simply discharged and recovered by the vaporized refrigerant inside the low-temperature rotor, but is used as a medium to cool the torque tubes, current leads, etc. in order to suppress the heat that enters the low-temperature rotor through heat conduction. Gas is used effectively and Tutu (A
n Approach to Optimag The
n'nd Design of 5 ups condu
cting Generator Rotor;
, 5ato.

et al. IEEE/PES, 1985. (8
55M 334-8)) has been recovered.

This conventional superconducting generator is arranged in a structure in which the end of the superconducting field winding on the collector ring side and the collector ring are electrically connected by penetrating the vacuum insulation space in a straight line in the axial direction. ing.

FIG. 5 shows a schematic layout of current leads of a conventional superconducting rotor. As shown in the figure, a low-temperature refrigerant flows in the direction of the arrow in the figure through the cooling path (2) inside the current lead (2) (usually a normally conducting conductor) insulated with an insulating material, cooling the current lead (ω). That is, by making the current lead (11) hollow and providing a cooling path (2) inside, it itself has the function of a heat exchanger. In order to suppress the heat entering the low temperature rotor ■ through the current lead ω,
It is common to consider the configuration of the cooling path (2) and reduce the cross-sectional area of the current leads.

In the structure of a conventional superconducting rotor, as mentioned above, a certain length is secured from the end of the field winding ■ on the collector ring (to) side to the collector ring (a), and the length is The length was approximately equal to the axial length of the torque tube 0 plus the axial length of the connecting shaft (2). In general, even if the generator capacity increases, the length of the current lead does not increase proportionally to the length of the torque tube 0 or joint shaft ■.
It was about m.

Incidentally, in recent years, attempts have been made to further improve the thermal performance (cooling performance) of superconducting rotors and to use refrigerants more efficiently, and consideration has been given to mounting superconducting conductors on small aircraft.

(Problems to be Solved by the Invention) As mentioned above, it is possible to reduce the heat entering the low-temperature rotor through the current lead without increasing the machine, especially the rotor shaft length.
Therefore, it is necessary to create a current lead structure with low heat penetration, but if a method is used to reduce the cross section of the current lead, the current density in the normally conducting part will increase, causing overheating of the current lead and eventually burnout. I'll wake you up.

In addition, in the ultra-fast adaptively excited superconducting generators that have been developed in recent years to improve system stability, the excitation voltage during long trips is several kV.
This increases dramatically compared to the conventional several volts, and therefore the current lead insulation thickness increases. This increases the cross-sectional area of the current lead and increases the amount of heat that enters.

The present invention has been made in view of the above circumstances.

The object is to provide a superconducting rotor with current leads that reduce the amount of heat conduction to the low temperature rotor.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a superconducting rotor in which current leads are cooled by flowing low-temperature gas inside them.
The present invention provides a superconducting rotor characterized in that the current leads are folded back multiple times in the axial direction in the vacuum insulation space within the torque tube.

(Function) With this structure, it is possible to increase the total length of the current lead by folding it, for example, without reducing the cross-sectional area of the normal conductor, or
Even in small-capacity machines with limited dimensions, the current lead length can be secured, reducing heat intrusion.Furthermore, the thick insulation coating of the current leads enables safe ultra-fast response excitation, resulting in high cooling performance and reliability. It is possible to provide a superconducting rotor with high performance.

(Example) Example 1 The following figures 1 and 2 show the first embodiment of the present invention.
This will be explained with reference to the figures. In addition, Fig. 1 and Fig. 21;! I
In the figure, the same parts as those in FIG. 5 of the conventional example are given the same reference numerals and explanations are omitted, and unexplained parts will be explained.
Please use this as a reference for understanding conventional examples.

The first stage current lead (la) made of normal current 4 conductors is connected to the superconducting rotor IiA■ at the end, and once connected to the first stage connection pipe (8a) having a U-shaped hole on the joint shaft ■ side. . A second stage current lead (1b) is connected to the first connection pipe (8a) by turning it back. The other end of the second stage current lead (1b) is connected to a second connecting pipe (8b) having a U-shaped hole, and the second connecting pipe (8b) is folded back and connected to the third stage current lead (1c). Concatenate. These current leads (l
The folding of a), (lb)=(lc) is performed in the vacuum insulation space 0 within the torque tube surrounded by the torque tube 0, the end face of the low temperature rotor (2), and the end face of the joint shaft (2). The folded opposite end of the third stage current lead (1c) passes through the joint shaft ■ in the same manner as the conventional installation method, and connects the connecting conductor (10
) to connect to the collector ring (a).

FIG. 2 shows a cross section of the current lead arranged in the vacuum insulation space 0 mentioned above, and shows the first lead 1' which has a cooling path .
2nd and 3rd stage current leads (la).

(lb) and (lc) are located on the small radius side from the center of the superconducting rotor, and are electrically insulating (11
) through the first, second and third vacuum pipes (12a).

(12b) and (12c) constitute a closed system.

The refrigerant supply pipe (21) and the refrigerant recovery pipe (22) form a refrigerant supply/discharge pipe (23), and after supplying liquid helium (24) to the field winding (a), gas helium (25) is One part passes through the current lead ω, and the gas helium exhaust hole (26)
The refrigerant is recovered from the remaining portion through the communication pipe (27), and the remaining refrigerant is recovered through the refrigerant recovery pipe (22).

Next, the operation of the first embodiment will be explained.

According to this embodiment, since the current lead (2) is folded back, the cooling medium passing through the current lead can be fully utilized, and the current lead ω length can be increased without increasing the rotor length. Since the amount of penetration can be reduced from a few minutes to an order of magnitude, it is possible to provide an extremely safe superconducting rotor that maintains a stable superconducting state of the superconducting wire in the low-temperature rotor. From the perspective of refrigerant consumption, it is possible to provide a machine with better cooling efficiency as the amount of heat that enters is reduced. This advantage is particularly magnified in small capacity machines. Furthermore, since the temperature gradient of the current lead is reduced, sufficient electrical insulation thickness can be secured without increasing the amount of heat transferred to the low-temperature rotor via the current lead compared to conventional methods, making it suitable for ultra-fast excitation type generators. is also effective and can significantly improve reliability.

In addition, conventionally, during cool-down, the exhaust gas from the current lead may reach minus 10 [C], which may cause a malfunction in the refrigerator system compressor installed in the exhaust loop (outside the generator body). However, in this embodiment, the current lead length is long and the amount of heat exchange is increased, so that the exhaust gas can be stably maintained at room temperature, and the reliability of the entire generator system can be improved.

Embodiment 2 FIG. 3 shows a second embodiment of the present invention, and is a view corresponding to the cross section of FIG. 2 showing the first embodiment.

That is, as the temperature increases, the electrical resistance of the conductor of the normal conduction current lead (2) increases, so the Joule loss in that part increases. Therefore, the cross-sectional area of the first stage current lead (la) in the low temperature part is larger than that of the current lead (1b) in the second stage and third stage in the high temperature part.
The method in which the cross section of (1c) is enlarged and folded back in the axial direction is basically the same as in the first embodiment.

In this way, each current lead (la) - (lb)
*The temperature gradient of (lc) becomes even smaller, and in addition, Example 1
The same effects can be obtained.

Embodiment 3 FIG. 4 shows a third embodiment of the present invention, and is a view corresponding to the cross section of FIG. 2 showing the first embodiment.

That is, this is an example in which the vacuum insulation space (b) in the torque tube in which the current lead is folded back does not have enough space in the radial direction, and is arranged with a phase shift in the circumferential direction.

The rest is the same as in Example 1.

In this way, the same effects as in the first embodiment can be obtained even with a small diameter rotor.

[Effects of the Invention] As explained above, according to the present invention, since the current leads are folded back and made longer, the cooling medium of the current leads can be fully utilized, and the current lead length can be increased without increasing the rotor length. Since the amount of heat penetration can be reduced from a few minutes to an order of magnitude, it is possible to provide an extremely safe superconducting rotor that maintains a stable superconducting state of the superconducting wire in the low-temperature rotor. From the perspective of refrigerant consumption, it is possible to provide a machine with better cooling efficiency as the amount of heat that enters is reduced. This advantage is particularly magnified in small capacity machines.

Furthermore, since the temperature gradient of the current lead is reduced, sufficient electrical insulation thickness can be secured without increasing the amount of heat transferred to the low-temperature rotor via the current lead compared to conventional methods, making it suitable for ultra-fast excitation type generators. is also effective and can significantly improve reliability.

In addition, conventionally, during cool-down, the exhaust gas from the current lead may reach minus 10 [C], which may cause a malfunction in the refrigerator system compressor installed in the exhaust loop (outside the generator body). However, in the present invention, since the current lead length is long and the amount of heat exchange is increased, the exhaust gas can be stably maintained at room temperature, and the reliability of the entire generator system can be improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of the upper half of a first embodiment of the superconducting rotor of the present invention, FIG. 2 is an enlarged sectional view taken along the line ■-■ in FIG. 1, and FIGS. FIG. 4 is a sectional view showing a portion corresponding to FIG. 2 of the second and third embodiments, and FIG. 5 is a vertical sectional view of the upper half of the conventional example. 1... Current lead, 5... Field winding, 6...
...Torque tube, 9...Vacuum insulation space, 25
...Helium is a low-temperature gas.

Claims (2)

[Claims] (1) A superconducting rotor in which current leads are cooled by flowing low-temperature gas therein, characterized in that the current leads are folded back multiple times in the axial direction in a vacuum insulation space within a torque tube. (2) The superconducting rotor according to claim 1, wherein the folded current leads have a larger current carrying cross-sectional area as they are connected to the room temperature side rather than the low temperature side.