JPH05326259A - Protection resistor for superconducting magnet with circuit opening/closing function - Google Patents

Abstract

PURPOSE:To protect a superconducting coil and a permanent current switch from burning by using an arrester as a circuit opening/closing device connected to a protection resistor in series. CONSTITUTION:The contacts of an arrester are kept open at a voltage produced across a superconducting coil 1 in magnetizing or demagnetizing operation; no circuit is constituted of the superconducting coil 1, a permanent current switch 2 and protection resistor 4. The contacts are closed at up to a voltage produced across the superconducting coil 1 in quenching thereof and at the occurrence of troubles in the permanent current switch 2; a circuit is constituted of the superconducting coil 1, permanent current switch 2 and protection resistor 4. This inhibits the shunt to the protection resistor 4 in magnetizing and demagnetizing operations, eliminating problems due to shunt. It also reduces the time of magnetizing/demagnetizing operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective resistor having a circuit opening / closing function for protecting a superconducting magnet when the superconducting coil is quenched or a trouble occurs in a permanent current switch.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional technique in which a protective resistor and a diode are not connected. 1 is a superconducting coil, 2 is a permanent current switch, 3 is a current lead wire, 4
Is a protective resistor, and 6 is a power source for excitation. In FIG. 3, the excitation power source 6 is cut off when the superconducting coil 1 is excited or demagnetized. The current flowing through the superconducting coil 1 flows through a closed circuit made up of the superconducting coil 1 in the superconducting state and the permanent current switch 2. A protective resistor 4 is incorporated in series with this circuit for the purpose of absorbing energy emitted from the circuit when an abnormality occurs in this circuit. Therefore, no means for connecting and disconnecting the superconducting coil 1 and the protective resistor 4 is provided. The excitation method will be described with reference to FIG. When exciting the superconducting magnet, the permanent current switch 2 is energized with the open state, a predetermined current is passed through the superconducting coil 1, and then the permanent current switch 2 is closed. As a result, the current of the superconducting coil 1 is in the permanent current mode even after the power source 6 for excitation is disconnected, and the current continues to flow inside to keep a strong magnet. Next, the degaussing method will be described. When demagnetizing the superconducting magnet, the superconducting coil 1 in the permanent current mode is energized from the exciting power source 6 with the permanent current switch 2 closed, and the current flowing in the superconducting coil 1 is started. After raising the current to the value, open the permanent current switch 2 and lower it to zero amperes. This eliminates the strong magnetic force of the superconducting coil 1. When the superconducting magnet is excited or demagnetized by such a method, the voltage V generated across the coil is V = L · (dI / dT). Here, L is the self-inductance of the superconducting coil 1, and dI / dT is the rate of change of the current flowing through the superconducting coil 1 when being excited or demagnetized. The voltage V causes a shunt to the protective resistor. FIG. 4 is an example of a conventional technique in which a protective resistor and a diode are connected.
1 is a superconducting coil, 2 is a permanent current switch, 3 is a current lead wire, 4 is a protective resistor, 6 is a power source for excitation, and 9 is a diode. In FIG. 4, the diode 9 incorporates the idea of blocking the current flowing in the protective resistor 4 in a specific direction. The excitation and demagnetization methods in this circuit are the same as in the case of FIG. 3, but since the diode is mounted in the direction that blocks the current flowing during excitation, it does not shunt to the resistor, thus shortening the excitation time. There is. The diode 9 may be considered as a thyristor in some cases.

[0003]

In the circuit configuration as shown in FIG. 3, not only when the superconducting coil is quenched or when a trouble occurs in the permanent current switch, which is the original purpose of the protection resistor, is not only the excitation that is usually performed frequently but Even during the degaussing work, the voltage V generated across the superconducting coil and the permanent current switch causes a shunt current to the protective resistor, which requires time for the exciting and degaussing work and causes a considerable heat loss in the resistor. Further, the method of disposing a diode in series with the protective resistor as shown in FIG. 4 to prevent shunting of current to the protective resistor during excitation is an effective means for solving the problem during excitation, but it occurs during degaussing work. Since the voltage goes in the opposite direction,
This means that the work time can be shortened and the diversion prevention function cannot be obtained. Therefore, there is an idea that a thyristor is used instead of a diode to prevent shunting in both directions.
However, as a protection system, it is required that the current flowing through the superconducting coil be surely passed through the protection resistor when an accident occurs. In the method that uses a thyristor,
When protection of the superconducting magnet is required, it is required to have a control function for conducting the thyristor. And the control function when adopting a thyristor is configurable, but in order to ensure the reliability of the protection function, it is desirable that the protection function be utilized without relying on an external signal,
There is a problem that the shunt blocking method using a thyristor is not always suitable as protective equipment.

[0004]

In order to solve the above problems, the voltage is higher than the voltage generated across the superconducting coil during excitation or degaussing work, and when the quench of the superconducting coil or the trouble of the permanent current switch occurs, the superconducting (EN) A protection resistor for protecting a superconducting coil and a persistent current switch from being burnt out by using a lightning arrester having a circuit configuration lower than a voltage generated across the coil.

[0005]

The protection resistor with a lightning arrester according to the present invention provides means for solving these problems. Under normal conditions, a circuit for protecting the superconducting magnet is not formed, but a specific voltage is applied. If it becomes above, a circuit will be comprised. As a result, if the value of this specific voltage is equal to or higher than the voltage generated during excitation / demagnetization, shunting to the protective resistor can be prevented during the excitation or degaussing work, and the value of this specific voltage will burn out the permanent current switch. Below the voltage,
Without externally operating the circuit to the protective resistor, the energy released in the event of a quench of the superconducting coil or a trouble of the persistent current switch can be sufficiently absorbed, and as a result, the protective resistor during excitation and degaussing work It is intended to solve the problems associated with diversion.

[0006]

1 is a circuit diagram of the present invention, and FIG. 2 is a block diagram of the present invention. 1 is a superconducting coil, 2 is a permanent current switch,
3 is a current lead wire, 4 is a protective resistor, 5 is a lightning arrester, 6 is a power source for excitation, 7 is a connection terminal, and 8 is a resistor housing container. Since the lightning arrester 5 is in a state where the contacts are opened by the voltage generated at both ends of the superconducting coil 1 during the excitation or degaussing work, the superconducting coil 1, the permanent current switch 2 and the protective resistor 4 are not configured in the circuit, and the superconducting coil 1 The contact is closed below the voltage generated at both ends of the superconducting coil 1 at the time of quenching or the trouble of the persistent current switch 2, and the superconducting coil 1, the persistent current switch 2, and the protective resistor 4 form a circuit configuration. Is. The mechanism of the present invention will be described with reference to FIG. When the superconducting coil 1 is energized or degaussed, the lightning arrester 5 keeps the circuit open, so no shunt to the protective resistor 4 occurs during both operations. Therefore, loss due to shunting can be eliminated and the work time can be shortened. When the superconducting coil 1 is quenched or the permanent current switch 2 has a trouble, the surge arrester 5 is closed by the voltage generated at both ends of the superconducting coil 1 or the persistent current switch 2, and is stored in the superconducting coil 1 as a strong magnetic field. This energy can be consumed by the protective resistor 4. FIG. 2 is an example of a specific configuration. Only the connection terminal 7 and the resistor housing container 8 are exposed to the outside. In the resistor housing container, the protective resistor 4 connected to the upper connection terminal 7 and the lightning arrester 5 connected to the lower connection terminal 7 are connected. It is connected.

[0007]

When the protection resistor with the lightning arrester according to the present invention is used as a protection resistance system, it has the following effects. 1. It is possible to prevent shunting to the protective resistor during excitation or degaussing work, and it is possible to solve the problem due to shunting. 2. It is possible to shorten the work time for excitation and demagnetization. 3. Since the current flows only when the superconducting coil is quenched and the permanent current switch has a trouble, which is the original role of the protective resistor, the protective resistor can be downsized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment according to the present invention.

FIG. 2 is a configuration diagram of an embodiment according to the present invention.

FIG. 3 is a circuit diagram when a diode is not connected in the related art.

FIG. 4 is a circuit diagram when a diode is connected according to the related art.

[Explanation of symbols]

 1 Superconducting coil 2 Permanent current switch 3 Current lead wire 4 Protective resistor 5 Lightning arrester 6 Power supply for excitation 7 Connection terminal 8 Resistor storage container 9 Diode

Claims (1)

[Claims] 1. A circuit connected in series with a protective resistor in a protection system provided in a room temperature range for the purpose of protecting the superconducting coil and the persistent current switch from burning out when the superconducting coil is quenched or a trouble occurs in the persistent current switch. A protective resistor for a superconducting magnet with a circuit switching function, characterized by using a lightning arrester as a switch.