JPH041485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting electromagnet device that can prevent dielectric breakdown of a superconducting electromagnet having a voltage application section in vacuum.

[Conventional technology]

Figure 2 is a circuit diagram showing a conventional superconducting electromagnet device, as shown on page 126 of ``Superconducting Engineering'' published by the Institute of Electrical Engineers of Japan. It is a low-temperature container, and together with the superconducting coil 1 constitutes a superconducting electromagnet 40 . R1 is a first protection element electrically connected between both ends of the superconducting coil 1, such as a first protection resistor, PS is an excitation power source that supplies current to the superconducting coil 1, and S1 is the superconducting coil 1 and the excitation power source
This is a current disconnection device that electrically connects or disconnects the PS. Note that these excitation power supply PS, first protection resistor R1, and current cutoff device S1 are connected to the excitation circuit 5.
Configure 0. The superconducting electromagnet device 60 includes a superconducting electromagnet 40 and an excitation circuit 50.

The conventional superconducting electromagnet device is configured as described above, and when the current cutoff device S1 is closed, the excitation power source is turned off.
Electric current is supplied from the PS to the superconducting coil 1, and electromagnetic energy is stored in the superconducting coil 1. However, if electrical resistance occurs in the superconducting coil 1 for some reason, (note that whether or not electrical resistance has occurred in the superconducting coil 1 is detected by a separately provided detection device (not shown), This detection device and the current shielding device S1 are designed to be linked.) The current shielding device S1 is opened and the current flowing through the superconducting coil 1 is transferred to the first protective resistor R1.
By causing the first protective resistor R1 to consume a part of the electromagnetic energy stored in the superconducting coil 1, the temperature rise in the superconducting coil 1 is reduced. If the temperature rise of the superconducting coil 1 is small, the time required to cool the superconducting coil 1 to a temperature at which it can be re-excited will be shortened, and the operating efficiency will be increased. When the current cutoff device S1 is opened, between both ends of the superconducting coil 1 (first protective resistor R
A voltage equal to the product of (current flowing through R1) and (resistance value of R1) is applied.

Next, let us consider the operation of a superconducting electromagnet device in which the superconducting coil 1 is placed in a vacuum. In this type of superconducting electromagnet, the cryogenic container 2
Heat intrusion into the superconducting coil 1 from the outer periphery of the superconducting coil 1 is blocked by the thermal resistance of the vacuum. However, while the superconducting coil 1 is being energized, if the vacuum atmosphere in which the superconducting coil 1 is installed deteriorates due to, for example, an abnormality in the vacuum evacuation equipment (not shown), and as a result the vacuum pressure increases, the superconducting coil 1 The heat entering the coil 1 is increased, the temperature of the superconducting coil 1 becomes high, electric resistance is generated, and the current breaker S1 is opened. When the current cutoff device S1 opens, a voltage having a magnitude equal to the product of the current value and the protective resistance value is applied between both ends of the superconducting coil 1, as described above. On the other hand, a part of the voltage application part of the superconducting coil, the current lead (not shown) electrically connected to the superconducting coil, and the voltage measurement line (not shown) for detecting the voltage of the superconducting coil is in a vacuum. They are often exposed to the environment naked. Electrical insulation when the voltage application part is in direct contact with the vacuum atmosphere is as follows:
Depends on the insulation resistance of the vacuum surrounding air. Figure 3 shows
An actual measurement example is shown in which the horizontal axis represents vacuum pressure and the vertical axis represents insulation resistance. From this measurement result, the electrical insulation resistance is sufficiently high at vacuum pressures of 10 ^-4 mmHg or less, where superconducting electromagnets are normally operated, but if the vacuum pressure increases due to some abnormality as mentioned above, the electrical insulation resistance will decrease dramatically. However, there was a possibility of dielectric breakdown occurring.

[Problem that the invention seeks to solve]

In conventional superconducting electromagnet devices, the vacuum pressure increases for some reason, electrical resistance occurs in the superconducting coil, and when the current cutoff device opens, the superconducting coil, whose electrical insulation resistance has decreased due to the vacuum pressure increase, and the current There was a problem in that voltage was applied to the leads and voltage measurement wires, destroying their insulation.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a superconducting electromagnet device that can reduce the voltage applied to the superconducting coil to prevent dielectric breakdown when the vacuum pressure is high. do.

[Means for solving problems]

The superconducting electromagnet device according to the present invention includes a pressure detection switch that detects the vacuum pressure when opening the current cutoff device, and an opening/closing switch that closes if the pressure detected by the pressure detection switch exceeds a predetermined value. The device is provided with a second protective element inserted into the excitation circuit by the switch.

In this invention, when the detected pressure exceeds a predetermined value, the protection resistor is switched to a smaller value and the voltage applied to the superconducting coil is lowered to prevent dielectric breakdown.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1, R1, S1 and PS are completely the same as those in the conventional device. 2A is a cryogenic container similar to cryogenic container 2. VS is a pressure detection switch, such as a vacuum switch, and is installed in a vacuum atmosphere [inside cryogenic container 2A] where all or any of the superconducting coil 1, current lead (not shown), and voltage measurement line (not shown) are in contact. It is used to determine whether the pressure of the vacuum surrounding air is high or low. Superconducting electromagnet 1
0 is these superconducting coil 1, cryogenic container 2A,
Consists of vacuum switch VS. R2 is the second
A protective element, for example a second protective resistor, is connected in series with the switch S2 and is connected in parallel with the first protective resistor R1 when the switch S2 is closed. The excitation circuit 20 includes the above-mentioned excitation power supply PS and current cutoff device S.
1, a switch S2, a first protective resistor R1, and a second protective resistor R2, and the superconducting electromagnet device 30 includes a superconducting electromagnet 10 and an excitation circuit 20.

Superconducting electromagnet device 3 configured as described above
0, the superconducting coil 1 is
At this time, the current cutoff device S1 is closed and the switch S2 is open. In this state, if electrical resistance occurs in the superconducting coil 1 for some reason and the vacuum switch VS indicates a predetermined vacuum pressure or lower (that is, normal pressure), the current is turned off with the switch S2 open. By opening the disconnection device S1, a current flows through the first protection resistor R1. When electrical resistance occurs in the superconducting coil 1 due to a vacuum abnormality, etc., the vacuum switch VS indicates a pressure exceeding the predetermined vacuum pressure (that is, abnormal pressure), first closes the switch S2, and then closes the current cutter S1. open, in this case the current flows through the first protective resistor R
1 and the second protective resistor R2, the voltage applied to the superconducting coil 1 can be lowered compared to the case of normal vacuum pressure, thereby preventing dielectric breakdown.

In the above embodiment, the first protection element and the second protection element are resistors, but they may be diodes or the like. Moreover, the current cutoff device S1 and the switch S2 may be a thyristor or a switch. Further, the protective resistor switching circuit does not need to be the one shown in FIG. 1, as long as it provides the same effect.

〔Effect of the invention〕

As described above, the present invention includes a pressure detection switch that determines whether the vacuum pressure is normal or abnormal, and a protective resistance value that is set to a small value if the vacuum pressure detected by the pressure detection switch exceeds a predetermined value. By providing the means, the voltage applied to the superconducting coil can be lowered to prevent dielectric breakdown, and a highly reliable superconducting electromagnet device can be obtained.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an embodiment of the present invention, Figure 2 is a circuit diagram of a conventional superconducting electromagnet device, and Figure 3 is an example of measuring insulation resistance of a superconducting electromagnet with a superconducting coil installed in vacuum. It is a diagram. In the figure, 1 is a superconducting coil, 2A is a cryogenic container, VS is a vacuum switch, S1 is a current breaker, S2 is a switch, R1 is a first protective resistor, R2 is a second protective resistor, 10 and 40 are Superconducting electromagnet, 2
0 and 50 are excitation circuits, and 30 and 60 are superconducting electromagnet devices. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A superconducting coil, a current lead and a voltage measurement wire electrically connected to the superconducting coil, a cryogenic container housing the superconducting coil, the current lead, and the voltage measurement wire, and the superconducting coil and the voltage measurement wire. A superconducting electromagnet having a pressure detection switch that detects the pressure of a vacuum atmosphere in which all or any of the current leads and the voltage measurement wires are installed, an excitation power source that supplies current to the superconducting coil, the superconducting coil and the excitation. a current interrupting device that electrically connects or disconnects the power supply; a first protection element electrically connected between both ends of the superconducting coil; and a first protection element connected in parallel with the first protection element via a switch. and an excitation circuit having two protection elements, and when the superconducting coil and the excitation power source are electrically disconnected, if the pressure detected by the pressure detection switch is less than a predetermined value, the switch and the current A superconducting electromagnet device characterized in that both of the cutoff devices are opened, but if the detected pressure exceeds the predetermined value, the switch is closed and only the current cutoff device is opened. 2. Claim 1, characterized in that the current cutoff device and the switch are thyristors and breakers.
The superconducting electromagnet device described in Section 1. 3. Claim 1 or 2, characterized in that the pressure detection switch is a vacuum switch.
The superconducting electromagnet device described in Section 1. 4. The superconducting electromagnet device according to any one of claims 1 to 3, wherein the first protection element and the second protection element are resistors. 5. The superconducting electromagnet device according to any one of claims 1 to 3, wherein the first protection element and the second protection element are diodes.