JP2694480B2 - Superconducting generator rotor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor of a superconducting generator, and more particularly, to a quench in the case where a transmission system accident or the like occurs by enhancing the cooling capacity of a superconducting field winding housed in the rotor. The present invention relates to a means for improving resistance to normal conduction transition.

[0002]

2. Description of the Related Art A cooling system for a rotor of a superconducting generator is disclosed in, for example, Japanese Examined Patent Publication No. 64-8538. In this example, the superconducting field winding is supported and fixed in the slot provided in the rotor winding mounting shaft. The liquid helium that cools the superconducting field winding flows in the radial direction from the outer circumference to the inside through the slot, passes through the through holes provided in the winding mounting shaft at the bottom of the slot, and passes through the liquid helium of the winding mounting shaft. Return to the refrigerant pool that stores the.

[0003]

In the prior art,
For example, when heat is generated due to AC loss during a short-circuit accident in the power transmission system, or when frictional heat is generated due to the movement of the superconducting conductor itself due to transient torque, there is a problem that the superconducting field winding is easily quenched. there were.

FIG . 5 is a sectional view schematically showing a structure around a superconducting field winding of a rotor of a conventional superconducting generator.
The supercritical pressure liquid helium 3 that is a refrigerant flows from the outer side to the inner side in the slot 5 of the winding mounting shaft 2 to which the superconducting field winding 1 is supported and fixed.

FIG. 2 is a view showing a cross section of the superconducting generator cut perpendicularly to its rotation axis. As shown in FIG. 2, the liquid helium originally exists in the coolant pool 4 at the center of the rotor, and once flows out radially outward at the magnetic pole portion of the winding mounting shaft 2 and then flows in the circumferential direction. Pour into 5.

[0006] In such a system, the thermal load basically acting on the flow does not change in both the steady state and the transient state, and the insufficient cooling performance is obtained in the transient state where more cooling capacity is required. There wasn't.

In other words, the cooling capacity could not be enhanced even in the situation where there is a short circuit accident in the power transmission system or heat is generated due to transient torque.

In order to solve this kind of problem, for example,
Kaihei No. 2-219458 is heat that heats liquid helium.
Generator and power supply and open / close switch for supplying heat to the heat generator
Than the local normal conducting part of the superconductor
Generate a large amount of heat, promote the convection of liquid helium,
Proposal of a method that can stably cool the local normal conducting part
I have.

However, in this method, a heat generator is provided.
Space must be secured, and power supply and open / close switch
It is necessary to devise the connection of the
Is it complicated to control the opening / closing timing of the open / close switch?
It was subtle.

The object of the present invention is to provide an external power source when heat is generated due to AC loss during a short-circuit accident in the power transmission system, or when frictional heat is generated due to the movement of the superconducting conductor itself due to transient torque.
The heat generator that is supplied with electricity from the
It is an object of the present invention to provide a rotor for a superconducting generator equipped with a means for enhancing the cooling capacity of the superconducting field winding and reliably preventing quenching without the need of providing an switch .

[0011]

In order to achieve the above object, the present invention provides a plurality of slots for accommodating superconducting field windings of a winding mounting shaft and liquid helium at the axial center of the winding mounting shaft. In a rotor of a superconducting generator in which a refrigerant reservoir to be stored is connected by a refrigerant passage hole, a superconducting generator in which a metal tube of an electric conductor having a lower electric resistance than the metal of the winding mounting shaft is formed in the refrigerant passage hole. The rotor is proposed.

The metal tube has, for example, a cylindrical shape, and can be provided with fin-shaped projections parallel to the flow of the refrigerant toward the refrigerant reservoir inside the cylinder.

The metal tube is specifically made of copper, copper alloy, aluminum, or aluminum alloy .

[0014]

Operation: The superconducting field winding is cooled by liquid helium. Liquid helium becomes supercritical pressure helium due to a large centrifugal force in the superconducting rotor, and does not cause a rapid phase change such as a boiling phenomenon. Therefore, its cooling capacity largely depends on the flow velocity of the refrigerant flowing through it.

Therefore, in the present invention, a heating portion utilizing Joule heat generation is provided in the flow path of the refrigerant, the density of the refrigerant passing through the portion is reduced, and a very large centrifugal force field in the superconducting rotor is obtained. The siphon effect is brought out by increasing the flow velocity of the refrigerant to improve the cooling performance during the transition.

Specifically, the Joule heat generated in the metal, which is a good electric conductor, by the asynchronous magnetic field acting on the rotor portion during the transition is utilized.

As a result, in the present invention, the external supply is used.
The heat generator to be charged and the power supply and open / close switch for it.
There is no need to install it, and there are multiple
Even if you do not perform coarse and delicate control,
Extraction of siphon effect due to extremely large centrifugal field
To increase the flow velocity of the refrigerant and improve the cooling performance during transition.
Can be.

[0018]

1 is a cross-sectional view schematically showing the structure of a superconducting field winding adopted in an embodiment of a rotor of a superconducting generator according to the present invention.

The flow path through which the refrigerant flows is basically the same as that of the prior art example shown in FIG. 5, so the same reference numerals are given and the description thereof is omitted.

In this embodiment, a metal tube 7 of a good electric conductor that forms a flow path is installed in the portion from the bottom of the slot 5 to the coolant reservoir 4 at the center of the winding mounting shaft 2. The tube 7 made of a good electric conductor is not limited to a cylinder as long as it has a cylindrical shape. For example, a polygonal cross section may be used. On the other hand, the winding mounting shaft 2 for supporting and fixing the superconducting field winding 1 is made of a metal having a relatively high electric resistance such as austenitic stainless steel or heat resistant alloy.

FIG. 3 is a diagram showing a configuration of an example of a power generation / transmission system using a superconducting generator including the rotor of FIG.
The superconducting generator 15 is connected to the transmission line 1 via the transformer 16.
7 is connected. The power transmission line 17 includes a breaker 18 that disconnects the power transmission system in the event of a short-circuit accident in the power transmission system, and is connected to the infinite bus bar 19.

When a short circuit accident occurs in the power transmission system as shown in FIG. 3, the following phenomena occur. In the axial cross section of the superconducting generator of FIG. 2, when the asynchronous magnetic flux accompanying the fault current from the air gap winding 13 enters the rotor, a part of the electromagnetic shield 12, the radiation shield 11 or the superconducting field winding is generated. Shielded by 1 itself.

However, the remaining components, particularly the component in the direction perpendicular to the superconducting field winding 1, penetrates into the winding mounting shaft 2 without being shielded so much. The asynchronous AC magnetic flux penetrating into the winding mounting shaft 2 induces an eddy current in the electric conductor tube 7 shown in FIG. 1 and causes a large Joule loss.

The liquid helium 3 for cooling the superconducting field winding 1 is in the coolant pool 4 at the center of the rotor, and as shown in FIG. 2, for example, in the magnetic pole portion of the winding mounting shaft 2,
Refrigerant reservoir 4 to winding mounting shaft 2 and helium vessel 10
It appears in the space formed between and. During this time, the liquid helium 3 becomes supercritical pressure helium due to the pressurization by the very large centrifugal force in the rotor, and abrupt phase change such as boiling phenomenon does not occur. After the supercritical pressure helium 3 flows in the circumferential direction in the space, it enters the slot 5 in which the superconducting field winding 1 is housed from the outside in the radial direction, and cools the superconducting field winding 1 in the slot. It returns to the original coolant reservoir 4 through the pipe 7 of a good electric conductor. The state of this flow is shown by an arrow.

The driving force for this refrigerant circulation is the centrifugal force and the heat entering the helium vessel 10 from the outside. Buoyancy acts on the supercritical pressure helium 3 which has been warmed by the heat of penetration and has a relatively low density, and moves toward the smaller radius. This is the origin of circulation.

On the other hand, the tube 7 of a good electrical conductor according to the present invention is
Joule loss occurs during the transition and heat is generated. This heat warms the supercritical pressure helium 3 flowing in the pipe portion, raises the temperature, relatively reduces the helium density, and a so-called thermosyphon effect can provide a large refrigerant circulation force.

The tube 7 made of a good electric conductor can be installed not only between the slot 5 and the coolant reservoir 4 in FIG. 1, that is, in the space or the magnetic pole part of the winding mounting shaft 2, but in this case, The supercritical helium 3 whose temperature has risen passes through the superconducting field winding portion 1 while returning to the refrigerant pool 4.
It is disadvantageous in terms of temperature margin.

The field winding mounting shaft 2 is acted upon by a speed of 2000 G or more in a centrifugal field. Therefore, the tube 7 having good electrical conductivity needs to have strength. As a material of the tube 7 having a good electric conductor, a metal having a low electric resistance and a required mechanical strength, such as copper, copper alloy, aluminum, or aluminum alloy, is suitable.

It is desirable that the tube 7 made of a good electric conductor has a large Joule heat generation and that the generated heat can be quickly transferred to the supercritical helium in the tube 7. Therefore,
As shown in FIG. 4, fins 9 placed in a direction parallel to the flow of the refrigerant and integrated with the tube wall may be formed inside the tube.

In the case of this structure, the eddy current due to the asynchronous magnetic flux flows along the wall of the tube 7 which is a good electrical conductor and the fin 9.
The Joule heat based on this eddy current is rapidly transferred to the supercritical pressure helium 3 from the large heat transfer surface of the fin 9 and the wall of the tube 7 which is a good electric conductor .

[0031]

According to the present invention, a heating element is provided in the refrigerant circulation path of the superconducting field winding, and when a short-circuit accident or the like occurs in the power transmission system connected to the generator, the internal temperature of the rotor is increased. Due to the thermosyphon effect using the centrifugal field, the cooling performance of the superconducting field winding can be enhanced and the quench of the field winding, that is, the normal conduction transition can be prevented.

Therefore, a heat generator that is supplied with power from the outside
There is no need to install a power source or open / close switch for
The opening and closing timing of the opening and closing switch is complicated and delicate.
You do not have to carry out control.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure around a superconducting field winding adopted in an embodiment of a rotor of a superconducting generator according to the present invention, which uses a metal tube having a good electric conductor.

FIG. 2 is a view showing a cross section of the superconducting generator cut perpendicularly to its rotation axis.

3 is a diagram showing a configuration of an example of a power generation / transmission system using a superconducting generator including the rotor of FIG.

FIG. 4 is a perspective view schematically showing the structure of an embodiment of a rotor of a superconducting generator according to the present invention, in which fins are provided in a metal cylinder of a good electric conductor.

FIG. 5: Superconducting field winding of rotor of conventional superconducting generator
It is a sectional view showing the structure of the circumference typically.

[Explanation of symbols]

1 superconducting field winding 2 winding mounting shaft 3 (supercritical pressure) liquid helium 4 refrigerant reservoir 5 slot 6 refrigerant passage hole 7 tube of good electric conductor 8 heater 9 fins 10 helium vessel 11 radiation shield 12 electromagnetic shield 13 void Armature winding 14 Magnetic shield (stator core) 15 Superconducting generator 16 Transformer 17 Transmission line 18 Circuit breaker 19 Infinity bus

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Maki 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Ltd. (56) References JP-A-56-74061 (JP, A) JP-A-55- 83439 (JP, A) JP-A-55-17299 (JP, A)

Claims (4)

(57) [Claims] 1. A superconducting generator in which a plurality of slots for accommodating a superconducting field winding of a winding mounting shaft and a refrigerant reservoir for accumulating liquid helium at the shaft center of the winding mounting shaft are connected by a refrigerant passage hole. The rotor of the superconducting generator according to claim 1, wherein a metal tube of an electric conductor having an electric resistance lower than that of the metal of the winding mounting shaft is formed in the refrigerant passage hole. 2. The rotor for a superconducting generator according to claim 1, wherein the metal tube has a cylindrical shape and has fin-shaped projections parallel to the flow of the refrigerant toward the refrigerant reservoir inside the cylinder. The rotor of the superconducting generator. 3. The rotor of a superconducting generator according to claim 1, wherein the metal tube is made of copper, copper alloy, aluminum, or aluminum alloy. 4. A superconducting generator equipped with the rotor according to claim 1 .