Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – Superconductive type
Reexamination Certificate
1998-03-30
2001-04-24
Donovan, Lincoln (Department: 2112)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
Superconductive type
C505S868000
Reexamination Certificate
active
06222434
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a superconducting toroidal magnet system.
In electrical power technology, the question of the extent to which superconducting magnet systems are suitable at appropriate cost for storing electrical energy has been the subject of recent investigation. Such systems are also known by the abbreviation SMES (Superconducting Magnetic Energy Store).
A superconducting energy store or accumulator is known, for instance, from European Patent 0 348 465 B1. The current store or accumulator shown therein has a toroidal coil system with many subcoils. The various subcoils or coil segments can be selectively connected in series or parallel and can be connected to a supply device for charging or discharging the entire configuration. It is also provided that for charging, for instance, only some of the coil segments are connected together. The interconnection of the coil segments can also be different for charging and for discharging. It is also possible for the energy store or accumulator to be loaded with a series circuit of some of the coil segments or all of the coil segments, and to discharge it in a parallel circuit.
In such superconducting magnet systems, what is known as a quench situation can arise, which can be considered a structural problem. In it, the superconduction is interrupted at one point in the superconductor by an excessive temperature increase.
The tripping event may be a very small local release of energy, which leads to a temperature increase of only a few degrees. However, since the superconductor is normally conductive, that is highly resistive, above its so-called transition temperature, the electrical current must be absorbed by so-called stabilizing material, for example highly conductive copper into which the superconductor is embedded. That leads to further local heating due to so-called Joulean losses, the heat spreads, and the normally conducting zone grows.
Unless countermeasures were taken, that process would not end until all of the energy inductively stored in the magnet of the system was dissipated. When large amounts of energy are stored, the temperature in the hot zone (“hot spot”) could become so high as to cause destruction of the magnet.
In order to overcome that problem, either as much energy as possible can be extracted (case a), or the heated zone in the magnet system can be increased spatially, so that the resultant maximum temperature is not as high (case b).
In case a, when there are large quantities of energy stored, a limitation exists through the use of the discharge voltage (because P=U×I!). The higher the voltage, the faster the energy can be extracted. The lower it is, the lower the maximum temperature which is then attained.
In case b, further quenching locations must be created in the magnet system. That can be carried out, for instance, by externally supplied quench heaters. However, the safety of the magnet system in the quench situation, after quenching is detected, depends on the tripping and functional reliability of the quench heaters. After that so-called secondary quench is created, the entire coil system may finally have to be run down until cold before operation can be resumed. Until then, the coil system is unavailable.
U.S. Pat. No. 5,146,383 discloses a superconducting magnetic energy storing system in which a plurality of magnet systems are divided into two groups. Each of the two groups has an associated supply device. A device for mutual takeover of current between the groups is provided. The magnet systems of the various groups are connected electrically in series.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a superconducting toroidal magnet system, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and in which operation can be at least partially maintained in a simple way, with as little energy as possible being dissipated, upon the occurrence of a quench.
With the foregoing and other objects in view there is provided, in accordance with the invention, a superconducting toroidal magnet system, comprising a plurality of annularly disposed magnet segments each assigned to one of at least two groups; common supply devices each connected to the magnet segments of a respective one of the groups, the common supply devices each including a device for mutual current takeover between the groups; and the magnet segments of the respective groups connected alternatingly in rings and each connected electrically in series.
In this way, an economical protection concept for the magnet system is provided, in which heating can be limited to the affected group in the quench situation. That is, the discharge takes place only for the affected group, so that despite the quench the overall system is still available with the capacity of the other groups. A quasi-automatic creation of secondary quenches occurs. In this process, largely physically automatic mechanisms are employed, which allow a reliable function of the magnet system without requiring expensive control devices. Moreover, the magnet system of the invention is available again more quickly after a failure, than a system of the prior art. That is, in the event of a failure, the energy of the system can be quasi-extracted or dissipated.
Preferably, the magnet segments of the groups are disposed alternatingly in rings. In this way, a uniform distribution of force and energy is provided.
The magnet segments of one group are preferably connected in series. In this way, the layout and the course of the conductors prove to be very simple, and the operating state of all of the individual magnets is always well-defined, regardless of any possible asymmetries.
In accordance with another feature of the invention, the supply devices of the various groups may be formed by an inverter, which may optionally be computer-controlled. Fast, reliable open-loop and closed-loop control of the magnet system is thus possible, and special operating modes or processes or monitoring operations are provided in the form of programs in the computer. This pertains especially to the function of current takeover, which establishes the energy equilibrium in the magnet system.
The magnet system is preferentially used as an energy store or accumulator with a large energy content for reserve purposes or buffer storage of energy and high-voltage or medium-voltage networks. Such a magnet system is rapidly available and because of its high operating safety is very reliable if there is a failure in the event of a quench.
In a preferred embodiment, the magnet system has only two groups, each with its own supply device. In this way, each magnet segment has a symmetrical environment, which is highly favorable with regard to the forces in the magnet system.
In accordance with a further feature of the invention, there is provided a sensor device for detecting a quench event, which is connected to the supply devices through a monitoring device. In this way, a targeted open-loop control of energy distribution, or even a closed-loop control, can be performed. This is especially favorable for active intervention in the event of a problem.
In accordance with an added feature of the invention, the supply devices have a low-impedance internal resistor as their device for mutual current takeover. This makes for an especially simple structure. This embodiment already provides improved performance as compared with the prior art.
In accordance with an additional feature of the invention, the groups are constructed to be galvanically or electrically separate. As a result, lower voltages to ground are possible.
In accordance with a concomitant feature of the invention, the magnet system serves as an energy store or accumulator.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a superconducting toroidal magnet system, it
Donovan Lincoln
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
LandOfFree
Superconducting toroidal magnet system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Superconducting toroidal magnet system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Superconducting toroidal magnet system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2478047