JPS58111304A - Superconducting electromagnet device - Google Patents

Abstract

PURPOSE:To shorten the time required for excitation and demagnetization, by detecting the current flowing through a shunt element in excitation or demagnetization, and supplying an output current corrected by the detected current value. CONSTITUTION:Both ends of a superconducting coil 2 housed in a cryostatic container 1 are connected to both ends of a variable-output DC power unit 21. A permanent current switch 5 and a protective resistor 6 are connected across the coil 2. In excitation or demagnetization, the unit 21 calculates the current flowing through a shunt element constituted by the resistor 6 and a resistor 13 of the switch 5 from the output voltage V and the output current Io and delivers an output current corrected by the calculated current value.

Description

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

Technical Background of the Invention In recent years, superconducting electromagnet devices have been used in not only stationary equipment but also rotating equipment. , which is mainly composed of a superconducting coil housed in this low-temperature container and a DC power supply that excites this superconducting coil6, and which can be operated by switching to persistent current mode. In some cases, a persistent current switch is provided in the low temperature container and selectively shorts 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.

FIG. 1 shows an example of a superconducting electromagnet device that can be switched to persistent current mode.
A thermal persistent current switch 5 is connected to the output end of the variable output DC power supply device 4 through a lead wire, and a thermal persistent current switch 5 is provided in the low temperature container 1 to selectively short-circuit both ends of the superconducting coil 2. A protective resistor C is provided between 1m and 31a. The persistent current switch 5 includes a switch body 11 made of superconducting wire, and a heater that selectively heats the switch body 11 by receiving input from the outside and switches it between a normal conduction mode (off) and a superconductivity mode (on). It consists of 12. Note that 13 in the figure indicates the equivalent resistance in the normal conduction mode.

Therefore, the device configured as described above switches to the persistent current mode (excitation) and cancels the persistent current mode (demagnetization) in the following manner. That is, during excitation, the heater 11 is energized and the switch body 11 of the persistent current switch 5 is turned off. , set to a predetermined value. next,
By stopping the power supply to the heater 1-, the switch body 11 of the persistent current switch 5 is turned on. Subsequently, the output current of the DC power supply device 4 is lowered to zero.

Through such control, a switch is made to the so-called persistent current mode in which a persistent current flows 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, the output current of the DC power supply device 4 is first increased to a value equal to the persistent current flowing through the superconducting coil 2, and then the heater 12 is energized to turn off the switch body 11 of the persistent current switch 5. Switch to In this state, the output current of the DC power S 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 changed from zero at the time of excitation and from the persistent current value at the time of demagnetization at a determined current increase rate (decrease rate). Therefore, there is a problem in that the time required for excitation and the time required for demagnetization are inevitably increased. 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 4 is increased as shown by 0, even if this output current reaches the set value at time t1, the current actually flowing through the superconducting coil 2 depends on its own inductance and the protective resistor 6. 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 becomes equal to the set value, as shown in FIG. , is time point 1. It's even more delayed. For this reason, not only does excitation take a long time, but also
Since it is necessary to energize the heater 12 of the persistent current switch 5, there is a problem in that there is 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, the conventional device has an increase rate (
Since the output current of the DC power supply device 4 is changed from zero (set value) at a decreasing rate), the above-mentioned problems cannot be avoided. Note that although H in FIG. 2 indicates the strength of the magnetic field generated in the superconducting coil 1, the present invention has been made in view of the above circumstances.
The purpose is to provide a superconducting electromagnet device that can shorten the time required for excitation and demagnetization.

Summary of the Invention The superconducting electromagnet device according to the present invention, as a DC power supply device, detects the current flowing through the shunt element from the output terminal voltage and the resistance value of the shunt element during excitation and demagnetization, and only the detected current value. It is characterized by using a configuration that sends out a modified output current.

Effects of the Invention Since the DC power supply device with the above configuration is used, a current with an increase rate (decrease rate) determined by the characteristics of this coil can be reliably passed through the superconducting coil during excitation and demagnetization, and as a result,
Excitation and demagnetization can be performed in the shortest allowable time determined by the characteristics of the superconducting coil. Therefore, compared to conventional devices, the time required for excitation and demagnetization can be shortened, and if the device can be switched to persistent current mode, the refrigerant loss per excitation 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.

This embodiment differs from the conventional device in the configuration of the DC power supply device 21. That is, the DC power supply device 21 can also output a negative output current, and when excitation and demagnetization are performed, the output terminal voltage V and the V-yant 22 produce an output of 1 current! . Detects this V,! , the output current ■ is controlled as follows. Now, the resistance value of the protective resistor 6 is RK, the resistance value of the first resistor of the persistent current switch 5 is ip, the parallel resistance value of Rx and RP is 8, and it is determined from the characteristics of the superconducting coil 2. The time function of the coil current “IL” is expressed as IL=K(t
When the general value of the coil current is 1M,
When the control signal P indicating the start of excitation is given, the output current increases as follows: When the control signal Q indicating the start of demagnetization is given, = (IM -LL) -V/B -------(
21 However, the maximum value of IL is configured to transmit an output range tlx* that decreases in the relationship IM. That is, in the above equation (11, tK1), since (■) is the protective resistance l and the resistance resistance during excitation and demagnetization, v/it is the current flowing through the parallel combined resistance, that is, the shunt element.In the device of the present invention, calculates R in advance, calculates V/R using this 8, sends out the output range ft,!, with v/R added when magnetizing, and subtracts V/R when demagnetizing. Therefore, the output current of the DC power supply 21 during excitation is as shown in the left half of Fig. 4, and at this time, the output current of the DC power supply 21 is The flowing current is shown by rL in the figure, and the strength of the magnetic field generated in the superconducting coil 2 is shown by H in the figure. In addition, during demagnetization, the current flowing through the superconducting coil 2 decreases at a rate selected depending on the characteristics of this coil, as shown in the right half of Figure 4. Therefore, excitation and demagnetization can be performed in the minimum allowable time T determined by the characteristics of the superconducting coil 2, which reduces the time required for excitation and demagnetization and reduces the refrigerant loss during excitation and demagnetization. In addition, during excitation, the current flowing through the superconducting coil 2 reaches the set value at the time when the output current of the DC power supply 21 reaches the maximum value, so the output current of the DC power supply 21 reaches the maximum value. By stopping the energization of the heater 12 when the value is reached, it is possible to generate the desired persistent current and the desired magnetic field.

In the above-mentioned embodiments, a DC current device that can send out the output current of the member is used, but it may be possible to send out only the positive output current. In this case, the rate of change in the current flowing through the superconducting coil at the final stage of demagnetization becomes gradual, but it does not have much of an effect.

Furthermore, it goes without saying that the present invention can also be applied to a device in which only a protective resistor is present and no persistent current switch is present. Further, the control signal and the detection body may be digitized and used.

[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 waveform examples of various parts during excitation and demagnetization of the same device, and Fig. 3 is a superconducting electromagnet according to an embodiment of the present invention. FIG. 4, a circuit diagram of the apparatus, is a diagram for explaining waveforms of various parts during excitation and demagnetization of the same embodiment. l...Low temperature container, 2...Superconducting coil, 511@I
I persistent current switch, d...protective resistor, 21...DC power supply device. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1, Figure 92, Figure 3, Figure 4

Claims (1)

[Claims] In a superconducting electromagnet device in which a variable output DC power supply device for excitation and demagnetization is connected to both ends of a superconducting coil constituting an electromagnet, and a shunt element is connected, the DC power supply device adjusts the output terminal voltage at the time of excitation and demagnetization. A superconducting electromagnet device characterized in that it is configured to detect a current flowing through the shunt element from the resistance value of the shunt element and to send out an output current corrected by the detected current value.