JPH02228007A - Superconducting magnet apparatus - Google Patents

Abstract

PURPOSE:To enhance reliability economically with a compact configuration by distributing and arranging circuit breakers not in a main DC circuit but for each unit circuit on the DC output side corresponding to each phase of the AC input of a converter. CONSTITUTION:This apparatus is composed of an exciting power source 1, a load 2, a transition detector 3 and a controller 4. The load 2 comprises a superconductor coil 5 which is formed by winding a superconductor. The exciting power source 1 comprises a converter 6, circuit breakers 7 which cut off the connection between the converter 6 and the superconductor coil 5 when the superconductor coil 5 is changed into the normal conducting state, a coil 8, a capacitor 9 and a protecting resistor 10. The converter 6 comprises two converter 6A each having an input terminal 11 of three-phase AC. The circuit breaker 7 is provided for every unit circuit on the DC output side corresponding to each phase of the AC input of a thyristor 6B. Six circuit breakers are provided for each thyristor 6B, and total of 12 circuit breakers are provided. In this way, the number of the circuit breakers can be decreased, and the compact configuration and the low cost are made possible. The possibility of the fail in circuit breaking can be decreased, and the reliability is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a superconducting magnet system, and particularly to a superconducting magnet system suitable for a nuclear fusion device or an energy storage device equipped with a high voltage/large current power source. do.

[Conventional technology]

Generally, a superconducting magnet system has a superconducting coil made by winding a superconductor, a converter that converts alternating current to direct current, and an excitation power source that controls the converter and energizes the superconducting coil. It is equipped with By the way, in a superconducting magnet system, it is necessary to protect the superconducting coil when the superconducting coil is transposed to a normal conducting state. For this reason, conventionally, as described in Japanese Patent Application Laid-Open No. 63-3405, a DC breaker was installed in the DC main circuit connecting the converter and the superconducting coil to detect when the superconducting coil has transitioned to normal conduction. When detected, this DC circuit breaker is opened to cut off the connection between the excitation power source and the superconducting coil, and the energy of the superconducting coil is consumed by a resistor connected in parallel to the superconducting coil to protect the superconducting coil. I was doing it.

[Problem to be solved by the invention]

However, in the above conventional technology, the DC circuit breaker is installed in the DC main circuit that connects the converter and the superconducting coil, so there is a limit to the capacity of the DC circuit breaker, and it is not suitable for nuclear fusion devices, energy storage devices, etc. There was a problem in that it was not compatible with the high voltage and large current systems used.

That is, there is an upper limit to the capacity of current DC circuit breakers, and large-capacity systems used in nuclear fusion devices and energy storage devices require the use of a large number of circuit breakers. This configuration is unrealistic in terms of space, wiring, and economy.

Furthermore, it is extremely difficult to operate a large number of circuit breakers at the same time, and when circuit breakers fail, there is a risk that the circuit components and even the load superconducting coils will be burnt out.

An object of the present invention is to provide a compact, economical, and highly reliable superconducting magnet system by appropriately installing a circuit breaker.

[Means to solve the problem]

The above object is achieved by distributing the circuit breakers not in the main DC circuit but in each unit circuit on the DC output side corresponding to each phase of the AC input of the converter.

The circuit breaker may be a mechanical circuit breaker or switch, but may also be a thyristor that interrupts the circuit by gate input.

[Effect]

The circuit breakers provided in each of the n DC output side unit circuits (arms) of the converter are normally closed, but operate to open the respective unit circuits during normal conduction transition. The current flowing through the unit circuit is 1/n of that of the DC main circuit, and unlike the current of the DC main circuit, it is a pulsating current that is interrupted by opening and closing of the conversion element. In other words, the current waveform flowing here is close to the current waveform immediately after half-wave rectification of single-phase AC,
The current is zero while the conversion element is open. Therefore, the circuit breaker placed here will interrupt the ripple current of 1/n in the main 9 circuits, and the current will become zero after at least half a cycle after the conversion element is closed. In the case of a mechanical circuit breaker, the snoke that occurs when the circuit is shut off disappears in a short period of time, and it operates more reliably than a DC circuit breaker, with less risk of circuit breakage failure. In addition, since sparks can be reliably extinguished, circuit breakers can be made smaller and lower in cost, and the number of circuit breakers can be reduced, making simultaneous operation easier, so there is a risk of failure due to difficulty in simultaneous operation. It also reduces

If a thyristor such as a GTO is used as a circuit breaker, the current will be zero after at least half a cycle after closing, so even if the reverse voltage for breaking is smaller than the peak value of pulsating current, it will be reliable. Can be blocked.

Therefore, it is possible to similarly reduce the risk of failure of circuit breaker, and also to reduce the capacity of the circuit breaker, making it possible to downsize and reduce costs. Also, the response of breaking is improved compared to mechanical circuit breakers.

When the opening operation of each unit circuit is completed, the DC output current flowing through the converter is commutated to the load superconducting coil, and the energy stored in the superconducting coil is converted into joules by the resistor connected in parallel. It is extracted as heat and prevents overheating damage to the superconducting coil.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, the superconducting magnet system of this embodiment is composed of an excitation power source 1, a load 2, a transition detector 3, and a controller 4, where the load 2 is a superconducting coil formed by winding a superconductor. It consists of 5.

The excitation power source 1 includes a converter 6 that converts alternating current into direct current in order to energize the superconducting coil 5, and a superconducting coil 5.
A circuit breaker 7 that disconnects the converter 6 and the superconducting coil 5 when the superconducting coil 5 changes to a normal conducting state, a coil 8 and a capacitor 9 that serve as filters, and a protective resistor provided in parallel with the superconducting coil 5. It consists of 10.

In this embodiment, the excitation power source 1 converts six-phase alternating current into direct current, and the converter 6 includes two sets of converters 6A, each having a three-phase alternating current input terminal 11.

Each converter 6A is composed of six thyristors 6B provided corresponding to each phase of the AC input, as shown in FIG. 2, and the circuit breaker 7 is provided in the output circuit 6C@ of the thyristor 6B. There is. That is, the circuit breaker 7 is provided for each unit circuit on the DC output side corresponding to each phase of the AC input of the thyristor converter 6A, and the number of circuit breakers is 12 in total, 6 for each thyristor converter 6A. be. Further, the circuit breaker 7 is constituted by an R mechanical circuit breaker, that is, a cutoff switch.

In the above-described superconducting magnet system, normally, the alternating current input from the alternating current input terminal 11 is converted to direct current by the thyristor converter 6, and the circuit breaker 7 in the closed state is converted to direct current by the thyristor converter 6.
, coil 8 and superconducting coil 5. However, when normal conduction transposition occurs in the superconducting coil 5, this superconducting magnet system operates as follows.

The transition detector 3 detects that the superconducting coil 5 has transitioned to a normal conduction state by detecting the resistance of the superconducting coil 5. The controller 4 receives the normal conduction transition occurrence signal from the transition detector 3 and opens each circuit breaker 7 .

When the circuit breaker 7 opens, the current flowing through the superconducting coil 5 is shunted from the converter 6 to the protective resistor 10, where the energy is recovered as Joule heat and the superconducting coil 5
and other circuit elements from overheating.

Here, in order to understand the operation of the circuit breaker 7 of this embodiment in more detail, consider a superconducting magnet system for nuclear fusion of, for example, 60,000 V or 30,000 A. In the conventional example, as shown in FIG. 4, a large number of DC circuit breakers 22 are installed in the DC main circuit connecting the F/A transformer 21 of the electric a20 and the superconducting coil 5. In this case, if the current maximum capacity class (1500V, 7500A) is used as the circuit breaker 22, the above high voltage, large current system would require 20 circuit breakers in 4 series and 5 parallel configurations. It's coming. For this reason, it is not only impractical in terms of space, economy, and economy, but also extremely difficult to operate 20 circuit breakers at the same time, and in the worst case, it may lead to failure. .

On the other hand, in this embodiment, since the circuit breaker 7 is provided in each of the six arms 6C of the thyristor converter 6, pulsating current is cut off, and the circuit breaker (60000V, 50000A) can not only be made smaller and lower in cost, but also fail to break. There will be no fear of

This will now be explained in detail using FIG.

Each unit circuit (arm) 6C on the DC output side of the converter 6
As shown in Fig. 3, unlike the current in the DC main circuit, a pulsating current flows intermittently due to the opening and closing of the thyristor 6B.
The amount of current of this pulsating current is 1/6 of the current of the DC main circuit.

That is, the current waveform flowing through the arm 6C is close to the current waveform immediately after half-wave rectification of single-phase alternating current, and the current is zero while the thyristor 6B is open. Therefore, the circuit breaker 7 placed here will interrupt 1/6 of the pulsating current in the main circuit, and the current will become zero after at least half a cycle after the thyristor 6B is closed. Even if a spark is generated when shutting off, the spark disappears in a short time, and it operates more reliably than DC shutoff, reducing the risk of failure. In addition, since sparks can be extinguished reliably, circuit breakers can be made smaller and lower in cost, and the number of circuit breakers can be reduced, making simultaneous operation easier, which prevents failures due to difficulty in simultaneous operation. It also reduces fear.

Another embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 shows a thyristor that has the function of breaking the circuit by a gate input, that is, a gate turn-off thyristor (GTO), in place of the mechanical breaker or switch 7 in FIG. 1.
) This is an example using 7A. In this case as well, GTO7A
is provided in each of the six arms 6C of the thyristor converter 6 (see Figure 2), and the current becomes zero after at least half a cycle after the thyristor is closed (see Figure 3). Even if the gate voltage for interrupting the GTO is smaller than the peak value of the pulsating flow, it can be reliably interrupted. Therefore, it is possible to similarly reduce the risk of failure of circuit breaker, and also to reduce the capacity of the circuit breaker, making it possible to downsize and reduce costs. G again
TO has an advantage over mechanical circuit breakers in that it has superior disconnection responsiveness.

Fig. 6 shows a circuit breaker equipped with a fuse 7B that can be forcibly blown from the outside using a trigger input terminal G. In this case as well, each arm 6C of the converter (see Fig. 2) should have a breaking function. Accordingly, the same effect as the embodiment shown in FIG. 1 can be obtained.

〔Effect of the invention〕

According to the present invention, since a circuit breaker is provided for each unit circuit on the DC output side of the converter, the number of circuit breakers can be reduced, the size can be reduced, the cost can be reduced, and the possibility of failure of circuit breaker can be reduced. , miniaturization of superconducting magnet systems, improvement of economic efficiency,
This has the effect of improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a superconducting magnet system according to an embodiment of the present invention, FIG. 2 is a detailed circuit diagram of the converter and circuit breaker portions of the superconducting magnet system, and FIG. FIG. 4 is a circuit diagram of a conventional superconducting magnet system, and FIG. 5 is a diagram showing a converter and a circuit breaker according to another embodiment of the present invention. FIG. 6 is a block diagram showing a converter and circuit breaker part according to still another embodiment of the present invention. Explanation of symbols 1... Excitation power source 5... Superconducting coil 6... Converter 6C... DC output side unit circuit 7... Breaker 7B... GTO

Claims (4)

[Claims] (1) A superconducting coil formed by winding a superconductor, a converter that converts alternating current to direct current, and when the superconducting coil transitions to a normal conduction state, communication between the converter and the superconducting coil is cut off. A superconducting magnet system including a circuit breaker and an excitation power supply that controls the converter and energizes the superconducting coil, wherein the circuit breaker is connected to a DC input corresponding to each phase of the AC input of the converter. A superconducting magnet system characterized by being provided for each unit circuit on the output side. (2) The superconducting magnet system according to claim 1, wherein the circuit breaker is constituted by a thyristor that interrupts the circuit by gate input. (3) It has a converter that converts alternating current into direct current and a circuit breaker that cuts off communication between the converter and the superconducting coil when the superconducting coil transitions to a normal conduction state, and controls the converter to An excitation power supply that energizes a conductive coil, wherein the breaker is provided for each output unit circuit corresponding to each phase of input AC of the converter. (4) A converter device for an excitation power source that has a converter that converts alternating current to direct current, and controls this converter to energize a superconducting coil, corresponding to each phase of the input alternating current of the converter. 1. A converter device characterized in that a circuit breaker is provided for each unit circuit of an output that cuts off communication between the converter and the superconducting coil when the superconducting coil transitions to a normal conduction state.