DC magnetic field superconducting coil power supply unit

Abstract

A superconducting coil power supply device for DC magnetic fields using a superconducting coil is realized at low cost. [Solution] A superconducting coil power supply device for a DC magnetic field comprises a superconducting coil, a power supply device capable of supplying DC voltage, a plurality of chopper circuits connected in parallel between one end of the power supply device and one end of the superconducting coil, a control unit that controls the chopper circuits, and a current sensor connected between one end of the power supply device and one end of the plurality of chopper circuits, and the control unit operates the plurality of chopper circuits in a time-division manner when the superconducting coil is being charged.

Description

[Technical Field]

[0001] The present disclosure relates to a DC magnetic field superconducting coil power supply device. [Background technology]

[0002] 2. Description of the Related Art DC magnetic field generators using superconducting coils have been known in the past. In order to generate a high magnetic field using a DC magnetic field generator using a superconducting coil, it is necessary to pass a large current through the superconducting coil.

[0003] As a technique for passing a large current through a superconducting coil, a technique is known in which the current passing through the superconducting coil is gradually increased to charge the superconducting coil, thereby passing a large current through the superconducting coil.

[0004] For example, Patent Document 1 discloses a technique for gradually increasing the current flowing through a superconducting magnet by repeatedly turning on and off a switch installed between an exciting transformer capable of supplying current and the superconducting magnet. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2011 / 074092 Summary of the Invention [Problem to be solved by the invention]

[0006] When charging a superconducting coil, a current is usually supplied to the superconducting coil from a power supply via a lead. Because a large current needs to be supplied, the power supply and the lead must be able to handle the large current, but power supplies and leads that can handle large currents are expensive.

[0007] An object of the present disclosure is to realize, at low cost, a DC magnetic field superconducting coil power supply device used in a DC magnetic field generating device using a superconducting coil. [Means for solving the problem]

[0008] The DC magnetic field superconducting coil power supply device according to the present disclosure comprises: a superconducting coil; a power supply device capable of supplying DC voltage; a plurality of chopper circuits connected in parallel between one end of the power supply device and one end of the superconducting coil; a control unit that controls the chopper circuit; a current sensor connected between one end of the power supply device and one end of the plurality of chopper circuits, The control unit operates the plurality of chopper circuits in a time-division manner when the superconducting coil is being charged.

[0009] In the DC magnetic field superconducting coil power supply device according to the present disclosure, The current sensor may detect a current flowing through an operating chopper circuit among the plurality of chopper circuits.

[0010] In the DC magnetic field superconducting coil power supply device according to the present disclosure, The control unit may adjust a duty ratio when operating each of the chopper circuits based on the current flowing through each chopper circuit detected by the current sensor.

[0011] In the DC magnetic field superconducting coil power supply device according to the present disclosure, The control unit may calculate the current flowing through the superconducting coil by adding up the currents flowing through the chopper circuits detected by the current sensors.

[0012] In the DC magnetic field superconducting coil power supply device according to the present disclosure, The superconducting coil, the plurality of chopper circuits, the current sensor, and the control unit may be installed inside a cooling vessel.

[0013] In the DC magnetic field superconducting coil power supply device according to the present disclosure, the superconducting coil, the plurality of chopper circuits, and the control unit are installed inside a cooling vessel, The current sensor may be installed outside the cooling vessel.

[0014] In the DC magnetic field superconducting coil power supply device according to the present disclosure, The superconducting coil and the plurality of chopper circuits may be installed inside a cooling vessel, and the current sensor and the control unit may be installed outside the cooling vessel.

[0015] In the DC magnetic field superconducting coil power supply device according to the present disclosure, further comprising a low resistance switch capable of short-circuiting both ends of the superconducting coil; When the current flowing through the superconducting coil reaches or exceeds a predetermined threshold, the control unit may stop charging the superconducting coil, and then control the low resistance switch to turn on to short-circuit both ends of the superconducting coil and transition to a non-charging state.

[0016] In the DC magnetic field superconducting coil power supply device according to the present disclosure, The control unit, in the non-charging state of the superconducting coil, controlling the low resistance switch to be off; The plurality of chopper circuits are operated in a time-division manner, and a current flowing through the operating chopper circuit is detected by the current sensor; The current flowing through the superconducting coil in the non-charging state may be calculated by adding up the currents flowing through the chopper circuits detected by the current sensors. [Effects of the Invention]

[0017] According to the present disclosure, a DC magnetic field superconducting coil power supply device using a superconducting coil can be realized at low cost. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing the configuration of a DC magnetic field superconducting coil power supply device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a chopper circuit. [Figure 3] FIG. 1 is a diagram illustrating an example of the configuration of a low-resistance switch. [Figure 4] 10 is a timing chart showing an example of the on / off timing of a switch of a chopper circuit. [Figure 5] 10 is a flowchart illustrating an example of the operation of a DC magnetic field superconducting coil power supply device according to an embodiment of the present disclosure. [Figure 6] 10 is a diagram showing an example in which the on / off timing of a chopper circuit switch, the detection result of the power supply current, and the inductor current are arranged in chronological order. [Figure 7] FIG. 10 is a diagram showing the configuration of a DC magnetic field superconducting coil power supply device according to a first modified example of the present disclosure. [Figure 8] FIG. 10 is a diagram showing an example of the on / off timing of the chopper circuit switch, the on / off timing of the low resistance switch, and the detection results of the power supply current when detecting the current flowing through the superconducting coil in a non-charging state, arranged in chronological order. [Figure 9] FIG. 10 is a diagram showing the configuration of a DC magnetic field superconducting coil power supply device according to a second modified example of the present disclosure. [Figure 10] FIG. 10 is a diagram showing the configuration of a DC magnetic field superconducting coil power supply device according to a third modified example of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0020] FIG. 1 is a diagram showing the configuration of a DC magnetic field superconducting coil power supply device 1 according to an embodiment of the present disclosure.

[0021] The DC magnetic field superconducting coil power supply device 1 includes a power supply device 11, first leads 12-1 to 12-2, chopper circuits 13-1 to 13-4, a low resistance switch 14, a current sensor 15, second leads 16-1 to 16-2, a superconducting coil 17, a control unit 18, and a current sensor 19 for detecting the superconducting coil current.

[0022] Hereinafter, the first leads 12-1 and 12-2 may be simply referred to as "first leads 12" when there is no particular need to distinguish between them.

[0023] Hereinafter, the chopper circuits 13-1 to 13-4 may be simply referred to as "chopper circuits 13" when there is no particular need to distinguish between them.

[0024] Hereinafter, the second leads 16-1 to 16-2 may be simply referred to as "second leads 16" when there is no particular need to distinguish between them.

[0025] First lead 12 , chopper circuit 13 , low resistance switch 14 , current sensor 15 , second lead 16 , superconducting coil 17 , control unit 18 and current sensor 19 for detecting superconducting coil current are installed inside cooling vessel 5 .

[0026] The cooling vessel 5 is a device capable of cooling the inside to a low temperature. For example, the cooling vessel 5 is capable of cooling the inside to about 20K.

[0027] The power supply device 11 is a device capable of supplying a DC voltage. The power supply device 11 may include, for example, an AC / DC converter that converts an AC voltage supplied from a commercial power source or the like into a DC voltage. The DC voltage supplied by the power supply device 11 may be, for example, about 3 V.

[0028] A first lead 12-1 and a first lead 12-2 are connected to two output terminals of the power supply device 11. One output terminal of the power supply device 11 is connected to a plurality of chopper circuits 13-1 to 13-4 via the first lead 12-1 and a current sensor 15. In this embodiment, the term "connected" means not only direct connection but also indirect connection. The other output terminal of the power supply device 11 is connected to the low-resistance switch 14 and a second lead 16-2 via the first lead 12-2. In addition, the first lead 12-2, the second lead 16-2, and the low-resistance switch 14 are connected to the ground of each chopper circuit 13.

[0029] The first lead 12 is a conductor capable of passing an electric current.

[0030] The plurality of chopper circuits 13-1 to 13-4 are connected in parallel between one end of the power supply device 11 and one end of the superconducting coil 17.

[0031] One of the plurality of chopper circuits 13-1 to 13-4 connected in parallel is connected to one end of power supply device 11 via current sensor 15 and first lead 12-1. The other of the plurality of chopper circuits 13-1 to 13-4 connected in parallel is connected to one end of superconducting coil 17 via current sensor 19 for detecting superconducting coil current and second lead 16-1. The ground of each chopper circuit 13 is connected to low resistance switch 14, and is connected to the other end of power supply device 11 via first lead 12-2 and the other end of superconducting coil 17 via second lead 16-2.

[0032] In this embodiment, a configuration in which four chopper circuits 13-1 to 13-4 are connected in parallel will be described as an example, but the number of chopper circuits 13 connected in parallel is not limited to 4. The number of chopper circuits 13 connected in parallel may be any number equal to or greater than two.

[0033] The chopper circuit 13-1 includes a first switch SA1, a second switch SB1, and an inductor L1. Similarly, the chopper circuit 13-2 includes a first switch SA2, a second switch SB2, and an inductor L2. Similarly, the chopper circuit 13-4 includes a first switch SA4, a second switch SB4, and an inductor L4. The chopper circuit 13-3 is not shown in FIG. 1.

[0034] Since the chopper circuits 13-1 to 13-4 have the same configuration, the chopper circuit 13-1 will be described as an example.

[0035] The first switch SA1 and inductor L1 of the chopper circuit 13-1 connect in series one end of the power supply device 11 and one end of the superconducting coil 17. The second switch SB1 connects a node between the first switch SA1 and the inductor L1 to ground.

[0036] Chopper circuit 13-1 charges superconducting coil 17 and inductor L1 with a current supplied from power supply device 11 when first switch SA1 is on and second switch SB1 is off.

[0037] The first switch SA1 and the second switch SB1 of the chopper circuit 13-1 are controlled by the control unit 18.

[0038] 2 shows an example of the circuit configuration of the chopper circuit 13-1. As shown in FIG. 2, the first switch SA1 and the second switch SB1 may be MOSFETs. The first switch SA1 may be a P-channel MOSFET. The second switch SB1 may be an N-channel MOSFET.

[0039] When the first switch SA1 and the second switch SB1 are MOSFETs, the gates of the MOSFETs are controlled by the control unit 18.

[0040] By using MOSFETs as the first switch SA1 and the second switch SB1, the operation speed of the first switch SA1 and the second switch SB1 can be increased. Furthermore, by using MOSFETs as the first switch SA1 and the second switch SB1, the on-resistance of the MOSFETs is small, so that the conduction loss of the first switch SA1 and the second switch SB1 can be reduced.

[0041] Since the chopper circuit 13-1 is installed inside the cooling container 5, the on-resistance of the first switch SA1 and the second switch SB1 is smaller than when they are installed at room temperature. Also, since the chopper circuit 13-1 is installed inside the cooling container 5, the series resistance value of the inductor L1 is smaller than when they are installed at room temperature.

[0042] Low resistance switch 14 is a switch capable of short-circuiting both ends of superconducting coil 17. One end of low resistance switch 14 is connected to one end of superconducting coil 17 via current sensor 19 for detecting superconducting coil current and second lead 16-1. The other end of low resistance switch 14 is connected to the other end of superconducting coil 17 via second lead 16-2.

[0043] It should be noted that low resistance switch 14 short-circuiting both ends of superconducting coil 17 does not mean a complete short circuit, but means that low resistance switch 14 connects both ends of superconducting coil 17 with a resistance value equal to or less than a predetermined resistance value. The predetermined resistance value may be, for example, about 0.01 to 0.1 mΩ.

[0044] The on / off of low-resistance switch 14 is controlled by control unit 18. While superconducting coil 17 is being charged, low-resistance switch 14 is off. That is, while superconducting coil 17 is being charged, low-resistance switch 14 does not short-circuit both ends of superconducting coil 17. When charging of superconducting coil 17 is completed, low-resistance switch 14 is turned on. That is, when charging of superconducting coil 17 is completed, low-resistance switch 14 short-circuits both ends of superconducting coil 17 and transitions to a non-charging state.

[0045] When charging of the superconducting coil 17 is completed and the low resistance switch 14 is turned on to transition to a non-charging state, current flows through the closed loop connecting the low resistance switch 14, the current sensor 19 for detecting the superconducting coil current, the second lead 16-1, the superconducting coil 17, and the second lead 16-2.

[0046] 3 shows an example of the circuit configuration of the low-resistance switch 14. The low-resistance switch 14 may have a configuration in which a plurality of parallel circuits, each of which is made up of a MOSFET 141 and a diode 142, are connected in parallel. The low-resistance switch 14 may also have a configuration including a MOSFET 141 having a plurality of parasitic diodes connected in parallel. The low-resistance switch 14 may have a configuration in which, for example, ten parallel circuits, each of which is made up of a MOSFET 141 and a diode 142, are connected in parallel. Note that the MOSFET 141 may be a type of circuit element other than a MOSFET, as long as it can function as a switch.

[0047] Since the low resistance switch 14 is installed inside the cooling vessel 5, the on-resistance of the MOSFET 141 is smaller than when it is installed at room temperature.

[0048] In this way, by configuring low resistance switch 14 to include low loss MOSFET 141, it is possible to reduce loss when current is passed through superconducting coil 17 in a closed loop.

[0049] The current sensor 15 is connected between one end of the power supply device 11 and one end of each of the plurality of chopper circuits 13-1 to 13-4. The current sensor 15 detects a current flowing through an operating chopper circuit 13 among the chopper circuits 13-1 to 13-4 that operate in a time-division manner. The current sensor 15 may be, for example, a CT (Current Transformer).

[0050] The second lead 16 is a conductor capable of passing a current. The second lead 16 may be, for example, a superconducting current lead. Since the resistance value of a superconducting current lead is approximately zero, the cross-sectional area of ​​the lead can be reduced. Therefore, the superconducting current lead has high thermal insulation properties, and can suppress the transfer of heat to the superconducting coil 17.

[0051] The superconducting coil 17 may include a coil formed from high-temperature superconducting wire. The superconducting coil 17 may be, for example, an uninsulated coil in which a metal tape of a relatively high-resistance normal-conducting material is sandwiched between coil-shaped high-temperature superconducting wire. If the superconducting coil 17 is an uninsulated coil, deterioration of the mechanical properties of the superconducting coil 17 can be prevented. Furthermore, if the superconducting coil 17 is an uninsulated coil, thermal runaway of the superconducting coil 17 can be suppressed, improving stability.

[0052] The control unit 18 controls the operation of the chopper circuit 13. The control unit 18 controls the operations of the chopper circuits 13-1 to 13-4 by controlling the first switches SA1 to SA4 and the second switches SB1 to SB4.

[0053] Control unit 18 operates multiple chopper circuits 13-1 to 13-4 in a time-division manner when charging superconducting coil 17. Details of the control of multiple chopper circuits 13-1 to 13-4 by control unit 18 will be described later.

[0054] The control unit 18 may have a configuration including a logic IC without including a processor such as a CPU (Central Processing Unit), or may have a configuration including a processor such as a CPU.

[0055] If the control unit 18 is configured not to include a processor such as a CPU, it is possible to improve the reliability of the control unit 18. Alternatively, if the control unit 18 is configured to include a processor such as a CPU, the control unit 18 can perform advanced processing.

[0056] Current sensor 19 for detecting superconducting coil current detects the current flowing through superconducting coil 17. Current sensor 19 for detecting superconducting coil current may be, for example, a CT (Current Transformer).

[0057] Next, the operation of the DC magnetic field superconducting coil power supply device 1 to charge the superconducting coil 17 will be described in detail.

[0058] When charging of superconducting coil 17 starts, control unit 18 controls low resistance switch 14 to be turned off.

[0059] Subsequently, the control unit 18 operates the plurality of chopper circuits 13 in a time-division manner to charge the superconducting coil 17 .

[0060] Operating the multiple chopper circuits 13 in a time-division manner means dividing the time of one cycle by the number of chopper circuits 13 and operating one chopper circuit 13 during each divided time. In other words, the control unit 18 operates each chopper circuit 13 once during one cycle.

[0061] 1, the number of chopper circuits 13 is four. Control of chopper circuits 13-1 to 13-4 by control unit 18 when the number of chopper circuits 13 is four will be described with reference to the timing chart shown in FIG.

[0062] The control unit 18 divides one cycle time into four, and in the example shown in FIG. 4, operates each chopper circuit 13 in turn for each 1 / 4 cycle time. One cycle is the time from t1 to t9. The control unit 18 operates chopper circuit 13-1 from t1 to t3. The control unit 18 operates chopper circuit 13-2 from t3 to t5. The control unit 18 operates chopper circuit 13-3 from t5 to t7. The control unit 18 operates chopper circuit 13-4 from t7 to t9.

[0063] Between t1 and t2, the control unit 18 controls the first switch SA1 of the chopper circuit 13-1 to be on and the second switch SB1 to be off. At this time, the control unit 18 controls the first switches SA2 to SA4 of the other chopper circuits 13-2 to 13-4 to be off and the second switches SB2 to SB4 to be on.

[0064] By this control, the inductor L1 and the superconducting coil 17 of the chopper circuit 13-1 are charged by the current supplied from the power supply device 11 between t1 and t2.

[0065] Subsequently, from t2 to t3, the control unit 18 controls the first switch SA1 of the chopper circuit 13-1 to be turned off and the second switch SB1 to be turned on. At this time, the control unit 18 controls the first switches SA2 to SA4 of the other chopper circuits 13-2 to 13-4 to be turned off and the second switches SB2 to SB4 to be turned on.

[0066] Subsequently, from t3 to t4, the control unit 18 controls the first switch SA2 of the chopper circuit 13-2 to be on and the second switch SB2 to be off. At this time, the control unit 18 controls the first switches SA1 and SA3 to SA4 of the other chopper circuits 13-1 and 13-3 to 13-4 to be off and the second switches SB1 and SB3 to SB4 to be on.

[0067] By this control, the inductor L2 and the superconducting coil 17 of the chopper circuit 13-2 are charged by the current supplied from the power supply device 11 from t3 to t4.

[0068] Subsequently, from t4 to t5, the control unit 18 controls the first switch SA2 of the chopper circuit 13-2 to be off and the second switch SB2 to be on. At this time, the control unit 18 controls the first switches SA1 and SA3 to SA4 of the other chopper circuits 13-1 and 13-3 to 13-4 to be off and the second switches SB1 and SB3 to SB4 to be on.

[0069] The control unit 18 repeats this process sequentially for the chopper circuits 13-3 to 13-4. When the operation of the chopper circuit 13-4 ends, that is, when t9 shown in Fig. 4 is reached, the control unit 18 returns to the process of operating the chopper circuit 13-1, and repeats the same process.

[0070] In this manner, control unit 18 charges superconducting coil 17 by repeating the processes shown in t1 to t9 in FIG.

[0071] While superconducting coil 17 is being charged, control unit 18 acquires the value of the current flowing through superconducting coil 17 from current sensor 19 for detecting superconducting coil current, which detects the current through superconducting coil 17. When control unit 18 determines that the current flowing through superconducting coil 17 has reached a predetermined threshold or more, it terminates the charging process for superconducting coil 17. Furthermore, when control unit 18 determines that the current flowing through superconducting coil 17 has reached a predetermined threshold or more, it controls low resistance switch 14 to turn on, short-circuiting both ends of superconducting coil 17 and transitioning to a non-charging state.

[0072] The predetermined threshold value may be the value of the current that needs to be passed through superconducting coil 17 in order to generate a predetermined DC magnetic field. The predetermined threshold value may be, for example, about 150A.

[0073] When the low resistance switch 14 is turned on, a current flows through a closed loop connecting the low resistance switch 14, the current sensor 19 for detecting the superconducting coil current, the second lead 16-1, the superconducting coil 17, and the second lead 16-2.

[0074] In this way, the DC magnetic field superconducting coil power supply device 1 according to this embodiment charges the superconducting coil 17 using four chopper circuits 13 connected in parallel. Therefore, when charging the superconducting coil 17 so that a current of 150 A flows through the superconducting coil 17, the average current flowing through one chopper circuit 13 is 150 A / 4=37.5 A.

[0075] Because chopper circuits 13-1 to 13-4 operate in a time-division manner, power supply device 11 only needs to be able to supply an average current of about 37.5 A. Therefore, power supply device 11 can be a low-cost power supply device compared to a power supply device that can supply 150 A.

[0076] Furthermore, when charging superconducting coil 17 so that a current of 150 A flows through superconducting coil 17, first lead 12 only needs to be able to pass a current of about 37.5 A on average. Therefore, the cross-sectional area of ​​first lead 12 can be made smaller than that of a current lead that can pass 150 A. By making the cross-sectional area of ​​first lead 12 smaller, the amount of heat that enters cooling vessel 5 from the outside through first lead 12 can be reduced.

[0077] Furthermore, each chopper circuit 13 only needs to be able to pass an average current of about 37.5 A. Therefore, the chopper circuit 13 can be made smaller than a chopper circuit that can pass 150 A. This makes it easier to install the chopper circuit 13 inside the cooling vessel 5.

[0078] When the charging process of superconducting coil 17 is completed, control unit 18 may control first switches SA1 to SA4 and second switches SB1 to SB4 of chopper circuits 13-1 to 13-4 to be turned off.

[0079] Alternatively, when the charging process of superconducting coil 17 is completed, control unit 18 may control first switches SA1 to SA4 of chopper circuits 13-1 to 13-4 to be turned off and second switches SB1 to SB4 of chopper circuits 13-1 to 13-4 to be turned on.

[0080] When the second switches SB1 to SB4 of the chopper circuits 13-1 to 13-4 are controlled to be turned on, the series configuration of the inductor L1 and the second switch SB1, the series configuration of the inductor L2 and the second switch SB2, and the series configuration of the inductor L4 and the second switch SB4 are connected in parallel to the low-resistance switch 14, and the resistance value across the low-resistance switch 14 when the low-resistance switch 14 is turned on can be further reduced. For example, when the resistance value of the series-parallel configuration of the inductors L1 to L4 and the second switches SB1 to SB4 when they are on is small, such as when the inductors L1 to L4 are superconducting coils, the low-resistance switch 14 may be omitted.

[0081] The control unit 18 can adjust the duty ratio when operating the chopper circuit 13. Taking the chopper circuit 13-1 as an example, the duty ratio is the ratio of the time during which the first switch SA1 is on to the time during which the chopper circuit 13-1 is operating. That is, in FIG. 4, if the time from t1 to t3 during which the chopper circuit 13-1 is operating is defined as TA, and the time from t1 to t2 during which the first switch SA1 is on is defined as TB, the duty ratio is expressed as TB / TA.

[0082] Control unit 18 can adjust the charging capacity for superconducting coil 17 by adjusting the duty ratio. For example, control unit 18 can maximize the charging capacity for superconducting coil 17 by setting the duty ratio close to 100%. Control unit 18 can also correct imbalances in currents of chopper circuits 13-1 to 13-4 by individually adjusting the duty ratios of chopper circuits 13-1 to 13-4.

[0083] The operation of the DC magnetic field superconducting coil power supply device 1 will be described with reference to the flowchart shown in FIG.

[0084] Control unit 18 controls low resistance switch 14 to be turned off (step S101). Thereafter, control unit 18 controls first switches SA1 to SA4 and second switches SB1 to SB4 of chopper circuits 13-1 to 13-4 as shown in the timing chart of FIG. 4, thereby charging superconducting coil 17 (step S102).

[0085] While charging superconducting coil 17, control unit 18 acquires the value of the current flowing through superconducting coil 17 detected by current sensor 19 for detecting superconducting coil current from current sensor 19 for detecting superconducting coil current (step S103).

[0086] Control unit 18 determines whether the current flowing through superconducting coil 17 is equal to or greater than a predetermined threshold value (step S104).

[0087] If the current flowing through superconducting coil 17 is less than the predetermined threshold value (No in step S104), control unit 18 returns to step S103.

[0088] If the current flowing through superconducting coil 17 is equal to or greater than the predetermined threshold (Yes in step S104), control unit 18 stops charging superconducting coil 17 (step S105). After stopping charging, control unit 18 controls low-resistance switch 14 to turn on (step S106).

[0089] <Correction of current imbalance in chopper circuits> FIG. 6 is a diagram showing, in the same time series, the operating states of the four chopper circuits 13-1 to 13-4, the power supply current detected by the current sensor 15, and the inductor currents flowing through the inductors L1 to L4.

[0090] 6 is a graph showing the operating state of chopper circuit 13. When the first switch SA1 is on and the second switch SB1 is off, chopper circuit 13-1 is on, and when the first switch SA1 is off and the second switch SB1 is on, chopper circuit 13-1 is off. The same applies to chopper circuits 13-2 to 13-4. That is, chopper circuit 13-1 is on from t1 to t2, chopper circuit 13-2 is on from t3 to t4, chopper circuit 13-3 is on from t5 to t6, and chopper circuit 13-4 is on from t7 to t8.

[0091] The middle graph in Figure 6 is a graph showing the power supply current detected by the current sensor 15. The chopper circuit 13 is controlled in a time-division manner, so that when the first switch SA1 of chopper circuit 13-1 is on and the second switch SB1 is off, the first switches SA2 to SA4 of the other chopper circuits 13-2 to 13-4 are off and the second switches SB2 to SB4 are on. Therefore, the power supply current flows only through the chopper circuit 13-1. In other words, the power supply current i1 from t1 to t2 flows only through the chopper circuit 13-1. Therefore, the current sensor 15 can detect the current i1 flowing through the chopper circuit 13-1 by detecting the power supply current from t1 to t2.

[0092] Similarly, current sensor 15 can measure current i2 flowing through chopper circuit 13-2 by detecting the power supply current from t3 to t4. Similarly, current sensor 15 can measure current i3 flowing through chopper circuit 13-3 by detecting the power supply current from t5 to t6. Similarly, current sensor 15 can measure current i4 flowing through chopper circuit 13-4 by detecting the power supply current from t7 to t8.

[0093] With the above-described configuration, the current sensor 15 can detect the current flowing through an operating chopper circuit among a plurality of chopper circuits that operate in a time-division manner.

[0094] It should be noted that no power supply current flows through any of the chopper circuits 13 during periods t2 to t3, t4 to t5, t6 to t7, and t8 to t9, and therefore the power supply current is zero.

[0095] The control unit 18 adjusts the duty ratio when operating each chopper circuit 13, based on the currents i1 to i4 flowing through each chopper circuit 13 measured by the current sensor 15. This allows the control unit 18 to correct the imbalance in the currents of the chopper circuits 13-1 to 13-4.

[0096] 6 is a graph showing the currents flowing through inductors L1 to L4 provided in chopper circuits 13-1 to 13-4. Inductors L1 to L4 are charged only while chopper circuits 13-1 to 13-4 including inductors L1 to L4 are on. For example, the current through inductor L1 increases only between t1 and t2 when chopper circuit 13-1 is on, and decreases between t2 and t9 when chopper circuit 13-1 is off.

[0097] (First Modification) A superconducting coil power supply device for a DC magnetic field 1a according to a first modified example of the present disclosure will be described below with reference to Fig. 7. Fig. 7 is a diagram showing the configuration of the superconducting coil power supply device for a DC magnetic field 1a according to the first modified example of the present disclosure. The superconducting coil power supply device for a DC magnetic field 1a is the same as the superconducting coil power supply device for a DC magnetic field 1 shown in Fig. 1 except that it does not include a current sensor 19 for detecting superconducting coil currents.

[0098] Current sensor 15 measures currents i1 to i4 flowing through chopper circuits 13-1 to 13-4, respectively. Control unit 18 adds up the measured currents i1 to i4 and calculates the result as the current flowing through superconducting coil 17.

[0099] Chopper circuits 13 are controlled in a time-division manner, so that only one of chopper circuits 13 is turned on. Therefore, by detecting and adding up currents i1 to i4 flowing through chopper circuits 13-1 to 13-4, the current flowing through superconducting coil 17 can be calculated.

[0100] With this configuration, it is possible to calculate the current flowing through the superconducting coil 17 without providing the current sensor 19 for detecting the superconducting coil current. The DC magnetic field superconducting coil power supply device 1a according to the first modified example can omit the current sensor 19 for detecting the superconducting coil current, thereby reducing costs accordingly.

[0101] <Current detection in the non-charging state after charging of the superconducting coil 17 is completed> Hereinafter, a method for detecting the current flowing through the superconducting coil 17 in a non-charging state after charging of the superconducting coil 17 is completed will be described in the superconducting coil power supply device 1a for a DC magnetic field according to the first modified example of the present disclosure shown in FIG. 7 in which the current sensor 19 for detecting the superconducting coil current is omitted.

[0102] In the DC magnetic field superconducting coil power supply device 1a, when charging of the superconducting coil 17 is completed and the superconducting coil 17 transitions to a non-charging state, the low resistance switch 14 is turned on, and current flows through the closed loop connecting the low resistance switch 14, the second lead 16-1, the superconducting coil 17, and the second lead 16-2.

[0103] In the DC magnetic field superconducting coil power supply device 1a, the current sensor 15 is connected outside the closed loop. Therefore, it is not possible to directly detect the current flowing through the superconducting coil 17. However, by performing the following process, the DC magnetic field superconducting coil power supply device 1a according to the first modified example can detect the current flowing through the superconducting coil 17 in the non-charging state.

[0104] Hereinafter, a method for detecting the current flowing through superconducting coil 17 in the non-charging state after charging of superconducting coil 17 is completed in DC magnetic field superconducting coil power supply device 1a will be described with reference to Fig. 8. Fig. 8 is a diagram showing the operating states of four chopper circuits 13-1 to 13-4, the states of the low resistance switches, and the power supply current detected by current sensor 15 in the same time series.

[0105] The control unit 18 turns off the low resistance switch 14, turns off the first switches SA1 to SA4 of the chopper circuits 13-1 to 13-4, and turns on the second switches SB1 to SB4.

[0106] Between t1 and t2, control unit 18 turns on first switch SA1 of chopper circuit 13-1 and turns off second switch SB1. At this time, first switches SA2 to SA4 of chopper circuits 13-2 to 13-4 are off and second switches SB2 to SB4 are on. Current sensor 15 detects the power supply current between t1 and t2 to detect current i'1 flowing through chopper circuit 13-1.

[0107] Similarly, current sensor 15 detects current i'2 flowing through chopper circuit 13-2 from t3 to t4. Similarly, current sensor 15 detects current i'3 flowing through chopper circuit 13-3 from t5 to t6. Similarly, current sensor 15 detects current i'4 flowing through chopper circuit 13-4 from t7 to t8.

[0108] Control unit 18 can calculate the current flowing through superconducting coil 17 in the non-charging state by adding together i'1 to i'4.

[0109] When control unit 18 completes detection of the current flowing through superconducting coil 17 in the non-charging state, it turns on low resistance switch 14, turns off first switches SA1 to SA4 of chopper circuits 13-1 to 13-4, and turns on second switches SB1 to SB4.

[0110] By adopting such a configuration, even in a non-charging state, the current flowing through the superconducting coil 17 can be calculated without the current sensor 19 for detecting the superconducting coil current, thereby reducing costs.

[0111] (Second Modification) A superconducting coil power supply device for a DC magnetic field 1b according to a second modified example of the present disclosure will be described below with reference to Fig. 9. Fig. 9 is a diagram showing the configuration of the superconducting coil power supply device for a DC magnetic field 1b according to the second modified example of the present disclosure. The superconducting coil power supply device for a DC magnetic field 1b is the same as the superconducting coil power supply device for a DC magnetic field 1a shown in Fig. 1, except that a current sensor 15 is installed outside the cooling vessel 5 and is connected between the power supply device 11 and the first lead 12-1.

[0112] The DC magnetic field superconducting coil power supply device 1b can be operated in the same manner as the DC magnetic field superconducting coil power supply device 1 and the DC magnetic field superconducting coil power supply device 1a, and can detect the current flowing in each of the chopper circuits 13-1 to 13-4 and the current flowing in the superconducting coil 17. By providing the current sensor 15 outside the cooling vessel 5, it is not necessary to make the current sensor 15 compatible with low temperatures, thereby reducing costs.

[0113] (Third Modification) A DC magnetic field superconducting coil power supply device 1c according to a third modified example of the present disclosure will be described below with reference to Fig. 10. Fig. 10 is a diagram showing the configuration of a DC magnetic field superconducting coil power supply device 1c according to the third modified example of the present disclosure. The DC magnetic field superconducting coil power supply device 1c is the same as the DC magnetic field superconducting coil power supply device 1b shown in Fig. 9 except that a control unit 18 is installed outside the cooling vessel 5.

[0114] The DC magnetic field superconducting coil power supply device 1c can be operated in the same manner as the DC magnetic field superconducting coil power supply device 1 and the DC magnetic field superconducting coil power supply device 1a, and can detect the current flowing in each of the chopper circuits 13-1 to 13-4 and the current flowing in the superconducting coil 17. By providing the current sensor 15 and the control unit 18 outside the cooling vessel 5, it is not necessary to make the current sensor 15 and the control unit 18 compatible with low temperatures, thereby reducing costs.

[0115] The present disclosure is not limited to the above-described embodiments. For example, multiple blocks shown in the block diagrams may be integrated, or a single block may be divided. Other modifications may be made without departing from the spirit of the present disclosure.

[0116] For example, in the above embodiment, an example has been described in which four chopper circuits 13 are connected in parallel, but the number of chopper circuits 13 connected in parallel may be any number equal to or greater than two.

[0117] For example, in the above-described embodiment, examples have been given in which current sensor 15 and control unit 18 are both installed inside cooling container 5, current sensor 15 is installed outside cooling container 5 and control unit 18 is installed inside cooling container 5, and both current sensor 15 and control unit 18 are installed outside cooling container 5. However, current sensor 15 may be installed inside cooling container 5 and control unit 18 may be installed outside cooling container 5. Alternatively, control unit 18 may be installed in different locations, such as by installing part of control unit 18 inside cooling container 5 and other part of control unit 18 outside cooling container 5. [Industrial Applicability]

[0118] The DC magnetic field superconducting coil power supply device of the present disclosure is suitable for applications in which a DC magnetic field is generated using a superconducting coil. [Explanation of symbols]

[0119] 1, 1a, 1b, 1c DC magnetic field superconducting coil power supply unit 5 Cooling container 11 Power supply 12 First Lead 13 Chopper Circuit 14 Low resistance switch 15 Current Sensor 16 Second Lead 17 Superconducting coil 18 Control Unit 19 Current sensor for detecting superconducting coil current L1~L4 inductors SA1~SA4 1st switch SB1~SB4 Second switch

Claims

1. a superconducting coil; a power supply device capable of supplying DC voltage; a plurality of chopper circuits connected in parallel between one end of the power supply device and one end of the superconducting coil; a control unit that controls the chopper circuit; a current sensor connected between one end of the power supply device and one end of the plurality of chopper circuits, The control unit operates the plurality of chopper circuits in a time-division manner when charging the superconducting coil.

2. 2. The DC magnetic field superconducting coil power supply device according to claim 1, The current sensor detects a current flowing through an operating chopper circuit among the plurality of chopper circuits.

3. 3. The DC magnetic field superconducting coil power supply device according to claim 2, The control unit adjusts a duty ratio when operating each chopper circuit based on the current flowing through each chopper circuit detected by the current sensor.

4. 3. The DC magnetic field superconducting coil power supply device according to claim 2, The control unit calculates the current flowing through the superconducting coil by adding up the currents flowing through each chopper circuit detected by the current sensors.

5. 2. The DC magnetic field superconducting coil power supply device according to claim 1, The superconducting coil power supply device for a DC magnetic field, wherein the superconducting coil, the plurality of chopper circuits, the current sensor, and the control unit are installed inside a cooling vessel.

6. 2. The DC magnetic field superconducting coil power supply device according to claim 1, the superconducting coil, the plurality of chopper circuits, and the control unit are installed inside a cooling vessel, The current sensor is installed outside the cooling vessel.

7. 2. The DC magnetic field superconducting coil power supply device according to claim 1, the superconducting coil and the plurality of chopper circuits are installed inside a cooling vessel, The current sensor and the control unit are installed outside the cooling vessel.

8. 3. The DC magnetic field superconducting coil power supply device according to claim 2, further comprising a low resistance switch capable of short-circuiting both ends of the superconducting coil; When the current flowing through the superconducting coil reaches or exceeds a predetermined threshold, the control unit stops charging the superconducting coil, and then controls the low resistance switch to turn on to short-circuit both ends of the superconducting coil, thereby transitioning to a non-charging state.

9. 9. The DC magnetic field superconducting coil power supply device according to claim 8, The control unit, in the non-charging state of the superconducting coil, controlling the low resistance switch to be off; The plurality of chopper circuits are operated in a time-division manner, and a current flowing through the operating chopper circuit is detected by the current sensor; The superconducting coil power supply device for a DC magnetic field calculates the current flowing through the superconducting coil in the non-charging state by adding up the currents flowing through each chopper circuit detected by the current sensors.

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