JPS58111305A - Superconducting electromagnet device - Google Patents

Abstract

PURPOSE:To shorten the time required for excitation and demagnetization, by detecting the magnetic field of a superconducting coil, and controlling the output current of a power unit so that the intensity of the magnetic field changes at a predetermined rate of change. CONSTITUTION:A magnetic field detecting element 21 for detecting the magnetic field generated in a superconducting coil 2 is provided in a cryostatic container 1. The output of the element 21 is supplied as a control signal Z for a DC power unit 23 through an amplifier 22 provided outside the container 1. When a signal P representative of the starting of excitation is introduced, the output current of the unit 23 is increased so that increase rate of the signal Z equals to the current increase rate determined by the characteristics of the coil 2. On the other hand, when a signal Q representative of the starting of demagnetization, is introduced, the output current is decreased so that the decrease rate of the signal Z equals to the current decrease rate determined by the characteristics of the coil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Distribution of the Invention The present invention relates to a superconducting electromagnet device in which a component that can serve as a current dividing element during excitation and demagnetization is provided between both ends of a superconducting coil constituting the electromagnet.

Technical Background of the Invention In recent years, superconducting electromagnet devices have been used not only in stationary equipment but also in rotary equipment. As is well known, a superconducting electromagnet device mainly consists of a low-temperature container whose interior is kept at an extremely low temperature, a superconducting coil housed in the low-temperature container, and a DC power supply that excites the superconducting coil. ing. If the superconducting coil can be switched to the persistent current mode for operation, a persistent current switch is provided in the low-temperature container to selectively short-circuit both ends of the superconducting coil. Further, generally, a protective resistor is connected between a pair of lead wires that connect the superconducting coil and a DC power supply located outside the low temperature container.

Figure 1 shows an example of a superconducting electromagnet device that can be switched to persistent current mode, in which both ends of a superconducting coil 1 housed in a low-temperature container 1 are connected to a variable output direct current via lead wires jm and 3b. A thermal persistent current switch 5 connected to the output end of the power supply device 4 and selectively shorting both ends of the superconducting coil 2 is provided in the low current container 1, and a protective resistor 6 is provided between the lead wires 34.3b. ing. The persistent current switch 5 includes a switch body 11 made of an i-conducting wire, and a switch body 11 that is selectively heated by input from the outside and switched to a normal conduction mode (off) and a superconductivity mode (on). It is composed of a heater 12. Note that 13 in the figure indicates the equivalent resistance in the normal conduction mode.

Therefore, the device configured as described above is configured to switch to the persistent current mode (excitation) and cancel the persistent current mode (demagnetize) in the following manner. That is, during excitation, the heater 12 is energized to turn off the switch body 11 of the persistent current switch 5, and in this state, the output current of the DC power supply 4 is linearly increased at a predetermined current increase rate, Set to a predetermined value. Next, the switch body 11 of the persistent current switch 5 is turned on by stopping the power supply to the heater 12. Subsequently, the output current of the DC power supply device 4 is lowered to zero. Through such control, a switch is made to a so-called persistent current mode in which a large current flows permanently in a closed circuit consisting of the superconducting coil 2 and the switch body 11 of the persistent current switch 5. In addition, during demagnetization, first, one output current of the DC power supply device 4 is increased to a value equal to the persistent current flowing through the superconducting coil 2, and then the heater 1z is energized to switch the switch body 11 of the persistent current switch 5. Switch off.

In this state, the output current of the DC power supply device 4 is decreased at a predetermined current reduction rate, and finally becomes zero. Then, the power supply to the heater 12 is stopped to complete the demagnetization control.

Problems with the Background Art The above-described control certainly makes it possible to switch to persistent current mode and eliminate persistent current mode. However, in conventional devices, the output current of the DC power supply during excitation and demagnetization is continuously determined from zero during excitation, and from the persistent current value during demagnetization.
Therefore, there is a problem in that the time required for excitation and the time required for demagnetization inevitably become longer. That is, during excitation, for example, the solid line in the left half of Figure 2! . When the output current of the DC power supply device 4 is increased as shown in , even if this output current reaches the set value at time t, the current actually flowing through the superconducting coil 2 depends on its own inductance and the protective resistance 6. And, due to the presence of the resistance associated with the normal conduction mode of the persistent current switch 5, that is, the presence of the shunt element, the current flowing through the superconducting coil 2 coincides with the set value, as shown in FIG. is considerably later than time t. Therefore, not only does excitation take a long time, but it is also necessary to energize the heater 12 of the persistent current switch 5 for that length of time, resulting in a large loss of refrigerant.

This was true not only during excitation but also during demagnetization as shown in the left half of FIG. During excitation and demagnetization, the rate of increase (rate of decrease) of the current flowing through the superconducting coil 2 is suppressed by the characteristics of the coil. Therefore, since the conventional device changes the output current of the DC power supply device 4 from zero (set value) at an increase rate (decrease rate) determined by the above-mentioned characteristics, the above-mentioned problems cannot be avoided. Note that H in FIG. 2 indicates the strength of the magnetic field generated in the superconducting coil 2.

OBJECTS OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to provide a superconducting electromagnet device that can shorten the time required for excitation and demagnetization. .

Overview of Isomei The superconducting electromagnet device according to the present invention is provided with magnetic field detection elements for detecting the strength of the magnetic field generated in the superconducting coil, and detects the magnetic field detected by the magnetic field detection element during excitation and demagnetization. The % characteristic is that a DC power supply device is provided that sends out an output current whose strength is determined and changes at a rate of change.

Effects of the Invention Let H be the strength of the magnetic field detected by the magnetic field detection element described above, and let IL be the current flowing through the superconducting coil at that time.
and the constant is K, then 1l-=KH-1--
-(11) Therefore, if the DC power supply device changes the output current so that the rate of change in the magnetic field strength H becomes equal to the current increase (decrease) rate determined by the characteristics of the superconducting coil, then A current !L with a rate of change determined by the characteristics of the superconducting coil flows through the superconducting coil.The device of the present invention utilizes the above-mentioned relationship.Therefore, the current !L is determined by the characteristics of the superconducting coil, regardless of the shunt element. Excitation and demagnetization can be performed in the shortest allowable time.Also, it is possible to always match the coil current and magnetic field strength to the target.Furthermore, with models that can be switched to persistent current mode, excitation and demagnetization can be performed in the shortest allowable time. Coolant loss during demagnetization can be reduced.

Embodiment of the Invention FIG. 3 shows a circuit configuration of a superconducting electromagnet device according to an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. Therefore, the explanation of the overlapping parts will be omitted.

8 In this embodiment, a magnetic field detection element 21 such as a pole element that detects the strength of the magnetic field generated by the superconducting coil l is provided in the low temperature vessel 1, and the output signal of this magnetic field detection element 21 is transmitted to the low temperature vessel 1. The signal is introduced as the control signal 2 of the DC power supply 23 via an externally provided amplifier 2z.

The DC power supply device 23 can also send out a negative output current, and when the signal P indicating the start of excitation is introduced, the control signal 2
Output current so that the rate of increase in is equal to the rate of increase in current determined by the characteristics of the superconducting coil l! . is increased until the magnitude of control signal 2 reaches a predetermined value. Furthermore, when the signal q indicating the start of demagnetization is introduced, the control signal 2
The output current 2 is reduced so that the rate of decrease in the current decrease rate is equal to the current decrease rate point determined by the characteristics of the superconducting coil 1, and the magnitude of the control signal 2 is decreased until the magnitude of the control signal 2 becomes zero.

Therefore, according to this device, during excitation, as shown in the left half of FIG. 4, the output current of the DC power supply J3!
. , the current flowing through superconducting coil 2! L and the magnetic field strength H change linearly, and a current IIl flows from zero through the superconducting coil 2 at an increasing rate determined by the characteristics of this coil. Similarly, during demagnetization, the fourth
As shown in the right half of the figure, in the superconducting coil 2
The flowing current will decrease at a rate determined by the characteristic number of this coil. For this reason, the allowable shortest time is determined by the characteristics of the superconducting coil 2. The time required for excitation and demagnetization can be significantly shortened compared to conventional devices. Also, since the coil current is controlled by detecting the strength of the magnetic field,
The coil current and magnetic field strength can always be adjusted to the target value.

In the embodiments described above, a DC power supply device capable of outputting a negative output current is used, or a DC power supply device capable of outputting only a positive output current may be used. In this case, the rate of change of the coil current becomes gradual in the final stage of demagnetization, but it does not have much of an effect. The present invention is also applicable to cases where a superconducting coil is wound around an iron core, where multiple superconducting coils are connected in series, where a persistent current switch is not present (however, a retaining resistor is present), etc. can.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a conventional superconducting electromagnet device, Fig. 2 is a diagram for explaining waveforms of various parts during excitation and demagnetization of the same device, and Fig. 3 is a superconducting electromagnet device according to an embodiment of the present invention. FIG. 4 is a diagram for explaining waveforms of various parts during excitation and demagnetization of the same embodiment device. 1... Low temperature container, 2... Superconducting coil, 11...
Magnetic field detection element, 13... DC power supply device.

Claims (1)

[Claims] A superconducting electromagnet device comprising: a superconducting coil constituting an electromagnet; The superconducting coil is equipped with a direct current power supply device whose output ends are connected to both ends of the superconducting coil and which controls an output current so that the strength of the magnetic field obtained by the magnetic field detection element changes at a predetermined rate of change during excitation and demagnetization. A superconducting electromagnet device characterized by: