JPH0449842A - Superconducting rotor - Google Patents

Abstract

PURPOSE:To obtain a superconductive rotor having highly reliable protection and monitoring function by arranging a liquid level detecting element such as a carbon resistance element at the liquid level position as the protection and monitoring for level drop of liquid helium. CONSTITUTION:A carbon resistance element 13 for alarm is attached to an insulating plate 12 provided to a coolant supply path 11 at the position in the side of inner diameter than the inner diameter position of coil attaching shaft and a carbon resistance element 14 for trip radially outside the carbon resistance element 13. When the liquid level drops up to the alarm setting point, the electrical resistance of the element 13 is rapidly reduced. An electrical signal of the element 13 is transferred to a comparator 17 through a slip ring and it compares the signal with the preset reference voltage to issue the alarm for drop of liquid level by driving an alarm circuit of an alarm/trip circuit 18. In the same manner, when the liquid level drops up to the trip setting point, the electrical resistance of the element 14 is reduced rapidly and the comparator 17 urgently stops a superconductive motor by driving a trip circuit of the alarm/trip circuit 18.

Description

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

(Prior Art) Conventionally, in the operation of a superconducting rotating electric machine, it has been important to monitor the liquid level of liquid helium, which is a refrigerant for maintaining a superconducting coil in a superconducting state. For this reason, superconducting liquid level needles are widely used in which a superconducting wire is arranged in the depth direction of the liquid and the liquid level is monitored by the electrical resistance of the superconducting wire. In addition, since the superconducting liquid level needle described above has problems in terms of mechanical strength and reliability when applied to rotating machines, carbon resistance pairs are connected in series in the depth direction of the liquid, and the electrical resistance A carbon resistance level needle may be used to monitor the level.

(Problems to be Solved by the Invention) In liquid level monitoring in a rotating machine, superconducting liquid level needles have problems in terms of mechanical strength as described above. Furthermore, in the carbon resistance liquid level needle, the boiling point of liquid helium rises due to an increase in internal pressure due to an increase in gravitational acceleration in a rotating field, so the electrical resistance of the carbon resistance changes. Therefore, the output (electrical resistance) of the level meter as a whole also changes, resulting in poor resolution as a level needle for monitoring the level. Therefore, when a superconducting coil is operated as a rotating machine, using a carbon resistance liquid level needle to protect and monitor the drop in liquid level poses a problem in reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a superconducting rotor having highly reliable protection and monitoring functions against a drop in liquid helium level in a superconducting rotating electric machine.

[Structure of the invention]

(Means for Solving Problem m1) In order to solve the above problems, in the present invention, the liquid level position of the alarm setting point, Alternatively, at the trip set point liquid level position.

Liquid level detection elements such as carbon resistance elements are arranged to detect whether the liquid level is above these positions.

The position of the alarm set point is on the inner diameter side of the inner diameter position of the winding installation shaft, and the position of the trip set point is on the outer diameter side including the inner diameter position of the winding installation shaft, and further than the inside diameter of the superconducting field winding. Arranged on the inner diameter side.

Further, the signal from the liquid level detection element is led to a comparator, and the judgment signal from the comparator drives the alarm or trip circuit of the protection/monitoring panel.

(Function) A carbon resistance element suddenly changes its electrical resistance characteristics at extremely low temperatures, and exhibits high electrical resistance.

The electrical resistance also varies greatly depending on the cooling state of the heat generated inside the carbon resistance element due to the weak current applied to measure the electrical resistance. That is, when the carbon resistance element is surrounded by liquid helium, the heat transfer coefficient is significantly higher than when the surrounding area R is gaseous helium, so that the electrical resistance exhibits a high value. By utilizing this characteristic, it is possible to determine whether the surroundings of the carbon resistance element are in a liquid phase or a gas phase. Similar functions also apply to temperature measuring elements such as germanium elements.

In other words, the above-mentioned characteristics of the 2I@ element are used to protect and monitor the drop in the liquid helium level in the rotor helium container. Since this method determines whether the liquid level is higher than the current level, it has better resolution and accuracy than a method that continuously monitors the liquid level using a liquid level needle or the like.

Additionally, the alarm set point or trip set point has the following meanings.

In a superconducting rotor, the liquid helium stored in the helium container sticks to the inner periphery of the helium container due to the centrifugal force caused by the rotation of the rotor, so the liquid level rises from the inner periphery of the helium container toward the inner diameter side. That will happen. On the other hand, for cooling the superconducting field windings.

The winding mounting shaft is provided with a refrigerant passage as in the conventional method. That is, a refrigerant supply passage from the inner diameter side of the winding attachment shaft to the outer diameter side, a passage connecting the field winding and the outer diameter side of the winding attachment shaft, and a passage connecting the field winding and the inner diameter side of the winding attachment shaft. Liquid helium is circulated through these passages to cool the field windings. If the liquid helium level drops below the inner diameter of the winding installation shaft, the refrigerant passage will be cut off, making it impossible to sufficiently cool the field winding in the event of an emergency such as a quench (normal conduction transition). There will be fears that are not there. Further, when the liquid level is lower than the inner diameter of the winding shaft, the amount of liquid helium stored is only in the refrigerant passage, and therefore the amount of liquid helium stored is insufficient for the above-mentioned emergency.

If the liquid level continues to drop for some reason and falls below the inner diameter position of the winding shaft, this is a situation in which operation must be stopped to protect the equipment.

Therefore, the trip set point should be provided on the outer diameter side including the inner diameter position of the winding attachment shaft and on the inner diameter side than the field winding inner diameter position. Also, the alarm set point should be set on the inner diameter side of the trip set point, considering the time margin until tripping, and therefore the alarm set point should be set on the inner diameter side of the winding installation shaft inner diameter position. .

In addition, the electrical resistance signal of the resistance element is led to a comparator, which determines whether the liquid level is above the mounting position of the temperature measuring element, and if the liquid level is low, activates a protection/monitoring alarm or trip circuit. This system protects and monitors superconducting rotating electrical machines against the drop in liquid helium level.

(Example) An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, a superconducting field winding 1 is held and fixed by a winding mounting shaft 2 and a wedge 3. On the outer diameter side,
A helium container 4 for holding liquid helium is installed. The above is kept at an extremely low temperature using liquid helium during operation. As a superconducting rotor, an outer cylinder 7 is installed on its outer diameter side as a heat insulating structure from a normal temperature part via a vacuum heat insulating part 5 and a radiation shield 6.

Further, in order to cool the superconducting field winding 1, there is a coolant passage 8 around the superconducting field winding 1, which is connected to the outer diameter of the winding mounting shaft through the communication holes 9 and 10 of the winding mounting shaft 2. It communicates with the side and inner diameter side. In addition to these, the winding mounting shaft 2
There is a refrigerant supply passage 11 that communicates between the inner and outer spaces, and these form a circulation path for liquid helium.

An insulating plate 12 installed in the refrigerant supply passage 11 has a carbon resistance element 13 for alarm on the inner diameter side of the shaft where the winding is attached, and a carbon resistance element 13 for alarm on the outer diameter side including the inner diameter of the winding attachment shaft. A carbon resistance element 14 is attached to the carbon resistance element 14, and a lead wire (not shown) for detecting electrical resistance is connected to each of the carbon resistance elements 14.

In FIG. 2, the electric resistance signals of the alarm carbon resistance element 13 and the trip carbon resistance element 14 are transmitted to the comparator 17, and the judgment signal is sent to the t-alarm trip circuit 18.
By driving the system, it protects and monitors the drop in liquid level. Also, for measuring the electrical resistance of carbon resistance elements,
In this example, a constant current source 19 is provided to supply a constant current to the carbon resistance element. Carbon resistance elements 13.14 are located on the rotation side, and comparators 17. Alarm/trip circuit 18
, and the constant current source 19 are located on the stationary side, the components on the rotating side and the stationary side are electrically interconnected via the slip ring 20.

During operation of the superconducting rotating electrical machine, if the liquid helium level starts to drop from the normal level for some reason, the alarm carbon resistance element 13
The electrical resistance of is rapidly reduced.

At this time, the alarm carbon resistance element 13 is supplied with a constant current from the constant current g19 through the slip ring 20.
The voltage drop decreases in proportion to the decrease in electrical resistance. The electrical resistance signal, that is, the voltage signal, of the alarm carbon resistance element 13 is transmitted to the comparator 17 through the slip ring 20, and the voltage is compared with a preset reference voltage, and the alarm circuit of 8 is connected to the alarm/trip circuit. The system is activated and issues an alarm for low liquid level. At this point, although some cause has occurred that lowers the liquid level, it is still possible to continue operating as a superconducting rotating electric machine.

Similarly, when the liquid level drops to the trip set point, the electrical resistance of the tripping carbon resistance element 14 decreases rapidly, and the comparator 17 drives the trip circuit of the alarm/trip circuit 18 to drive the superconducting rotating electrical machine. Perform emergency stop operation. At this point, it is dangerous to continue driving any further.

As described above, in this embodiment, since the drop in the liquid level is monitored at each of the alarm set point or the trip set point to see whether the liquid level is higher than that position, the resolution is good and the accuracy is high.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, a germanium element or the like may be used as a resistance element used as a detection element for alarm or trip for low liquid level. In measurement,
In addition to the voltage drop measurement by constant current supply shown in the above embodiment, current measurement by constant voltage supply may also be used.

Furthermore, in the above embodiment, the rotation side and the stationary side are interconnected via the slip ring 20, but in addition, a temperature measuring element, a comparator, a constant current source, etc. are provided on the rotation side, and the comparator issues an alarm.・The trip circuit drive signal is transmitted to the alarm located on the stationary side by non-contact signal transmission means such as optical signals or radio signals such as FM.
The signal may be transmitted to a trip circuit to perform protection and monitoring operations.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a superconducting rotor having a high resolution and reliable liquid level drop protection/monitoring function against a drop in liquid helium level during operation of the rotor.

[Brief explanation of drawings]

1st y! I is a cross-sectional view of a superconducting rotor that is an embodiment of the present invention, FIG. 2 is a block diagram for explaining liquid level drop protection and monitoring of the superconducting rotor shown in FIG. 1, and FIG. FIG. 1 is a longitudinal cross-sectional view of a superconducting rotor, and FIG. 4 is a cross-sectional view of a conventional superconducting rotor. l...Superconducting field winding 2...Winding mounting shaft 4...
Helium container 13...Carbon resistance element for alarm 14...Carbon resistance element for trip Agent Patent attorney Noriyuki Chika Illustration

Claims (2)

[Claims] (1) In a superconducting field winding formed by winding a superconducting conductor and held by a hollow cylindrical winding mounting shaft, and in a superconducting rotor having a helium container on the outer periphery of the winding mounting shaft, the winding mounting shaft A superconducting rotor characterized in that a liquid level detection device is provided for detecting changes in the liquid helium level in a helium container in a radial direction. (2) The liquid level detection device is located inside the inner diameter position of the winding mounting shaft for the alarm set point, and outside of the inner diameter position of the winding mounting shaft and inside the field winding for the trip set point. The superconducting rotor according to claim 1, wherein the superconducting rotor is disposed on the inner diameter side.