JPH0560274B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is a combination of a superconducting magnet and a refrigerant refrigerator, and is applicable to a superconducting electromagnet device used in, for example, a single crystal growth device or a nuclear magnetic resonance device. Regarding improvements. [Technical Background of the Invention] An example of a conventional superconducting electromagnet device of this type is one constructed as shown in FIG. That is, a radiation shield plate 2 is arranged inside an outer tank 1, an inner tank 3 is arranged inside this, and a cold storage container 4 is constituted by these. The inner tank 3 is kept at an extremely low temperature, e.g. 4.2K, by a refrigerant refrigerator which will be described later.
A superconducting coil 6 is supported within the inner tank 3 by a superconducting coil support material (not shown). This superconducting coil 6 is electrically connected to one end of a power lead 7, and the other end of this power lead 7 is provided so that one end is located in a normal temperature space outside the cold storage container 4, and the power lead One end of the superconducting coil 7 is electrically connected to an external power source 8, so that the superconducting coil 6 can be excited. One end of a pressure relief pipe 9 is connected to the inner tank 3 so that abnormal helium gas pressure generated within the inner tank 3 can be released to the outside of the outer tank 1, and the other end of the pressure release pipe 9 is connected to the inner tank 3. is located in the external space, and a mechanical pressure relief device 10 and a rupture disk pressure relief device 11 are connected to the other end of the pressure relief pipe. The mechanical pressure relief device 10 has a structure in which the valve body is in an open state when a predetermined pressure is exceeded, and the valve body is in a closed state when the pressure is less than a predetermined pressure. The rupture disk type pressure relief device 11 is constructed such that the member closing the opening of the container ruptures when abnormal pressure occurs. For example, a helium refrigerator (hereinafter referred to as a refrigerator) 12 is used as the refrigerant refrigerator, and is configured as follows. A refrigerator head 13 is provided on the external upper wall surface of the outer tank 1, and a compressor 16 for compressing helium is connected to a refrigerant inflow pipe 14 and a refrigerant return pipe 15 of this refrigerator head 13. is directly connected to an electric motor 17 for driving it. The above refrigerator head 1
3 is provided with a first stage cooler 18 which is disposed inside the outer tank 1 and outside the radiation shield plate 2 for cooling the power lead 7 and the radiation shield plate 2. The first-stage cooler 18 is provided with a second-stage cooler 19 located within the radiation shield plate 2 and for cooling the power lead 7 . The first stage cooler 18 and the second stage cooler 1
9 are pistons (not shown) that compress and expand helium driven by a piston drive mechanism (not shown) included in the refrigerator head 13.
It consists of a cold storage material (not shown) that stores helium cooled by the compression and expansion action of the piston, and members that serve both mechanical support and heat conduction, such as flanges 18A and 19A. The flange 18A of the first stage cooler 18 is mechanically and thermally connected to the radiation shield plate 2, and
Flange 18A of stage cooler 18 and power lead 7
The first-stage heat station 20 is mechanically and heat-transferably connected to the first-stage heat station 20 by a heat-transfer member 21 with good thermal conductivity, and the flange 19A of the second-stage cooler 19 and the first-stage power lead 7 Similarly, it is connected to the two-stage heat station 22 by a heat transfer member 23. Inside the inner tank 3, there is liquid helium 5
A helium recondenser (hereinafter referred to as recondenser) 2 is used to recondense the helium gas generated by evaporation.
4 is provided, and one ends of a J-T inflow pipe 25 and a J-T return pipe 26 are connected to the inlet and outlet sides of the recondenser 24. The other ends of this J-T inflow pipe 25 and J-T return pipe 26 are
It is connected to the refrigerant inflow pipe 14 and the refrigerant return pipe 15 connected to the inlet and outlet sides of the refrigerator head 13, and a first stage The inflow side of the heat exchanger 27, the inflow side of the second stage heat exchanger 28, and the inflow side of the third stage heat exchanger 29 are connected in series. A flange 18A of the first stage cooler 18 is fixedly inserted through the J-T inflow pipe 25 to which the first stage heat exchanger 27 and the second stage heat exchanger 28 are connected. Further, a flange 19A of the second stage cooler 19 is fixedly penetrated in the middle of the J-T inflow pipe 25 to which the second stage heat exchanger 28 and the third stage heat exchanger 29 are connected. There is.
J-T
A valve 30 is provided. Above J-T return piping 2
6 includes the first, second and third stage heat exchangers 2;
The outflow sides of 7, 28, and 29 are connected in series. The refrigerator 12 is configured in this way. Next, the operation of the conventional superconducting magnet device configured as described above will be explained. One end of the power lead 7 is located in a room temperature space (for example, 300K), and the other end is located inside the inner tank 3 via the outer tank 1 and the radiation shield plate 2, so that the action of the power lead 7 is That is, heat conduction,
Heat from the room-temperature space enters the inner tank 3 due to thermal radiation, and the liquid helium 5, which is at an extremely low temperature (for example, 4.2 K), evaporates. In order to minimize the evaporation of this liquid helium 5, a radiation shield plate 2 is provided inside the outer tank 1.
This radiation shield plate 2 is cooled to 70 to 100 K by a first stage cooler 18. Of the heat that enters from the outside room temperature space, the largest amount is the heat that is transmitted from the power lead 7. In order to reduce this intrusion heat, the power lead 7
Heat station 20 cooled to 70-100K
And it is forcibly cooled by a heat station 22 cooled to 10 to 20K. Normally, due to such a reduction in heat intrusion, the amount of evaporation of the liquid helium 5 in the inner tank 3 becomes a small value of 1 to 2/h. This evaporated helium gas is condensed (liquefied) in the recondenser 24, which is cooled to 4.2K.
It becomes liquid helium and returns to the inner tank 3. In this way, the superconducting magnet device can be operated continuously without re-injecting liquid helium. [Problems with Background Art] However, the conventional superconducting magnet device configured as described above has the following drawbacks. The amount of heat that enters through the power lead 7 is proportional to the excitation current value from the external power source 8, as shown in the equation. Q _p = I・√・( _h ² − _c ² ) ... Here, Q _p : Amount of heat intruded from the power lead 7 I: Excitation current value α: Constant (p: power lead resistivity, T: temperature K: Thermal conductivity of the power lead 7 T _h : Temperature of the high temperature part T _c : Temperature of the low temperature part For example, T _h is the temperature of the heat station 22
Set to 10K to 20K, and T _c is the temperature of liquid helium 5.
If it is set to 4.2K, Q _p is the amount of heat that enters the liquid helium, and the liquid helium evaporates due to the heat of vaporization corresponding to this heat. When there is a request to vary the magnetic field generated by the superconducting coil 6 (for example, when used in a single crystal growth device or a nuclear magnetic resonance device), the excitation current value I is changed in proportion to the magnetic field strength, so the formula can be used. In this case, the amount of heat Q _p will change accordingly. Therefore, the amount of liquid helium evaporated will also vary. Here, let us consider the refrigeration operation of the refrigerator 12 . Helium gas in the compressor 16 is driven and compressed by an electric motor 17, and is connected to a refrigerant inflow pipe 14, a refrigerator head 13, a first stage cooler 18, a second stage cooler 19,
The refrigerant flows in a circulation loop that returns to the compressor 16 through the refrigerant return pipe 15. At this time, the helium gas expands adiabatically in the refrigerator head 13, and the first stage cooler 18 heats up to 100K due to the exchange of heat at this time.
~70K, the second stage cooler 19 is cooled to 10K-20K. On the other hand, a part of the helium gas discharged from the compressor 16 is branched from the refrigerant inflow pipe 14 and
- Flows into the T inflow pipe 25. This helium gas passes through the first stage heat exchanger 27, the first stage cooler 18, the second stage heat exchanger 28, the second stage cooler 19, and the third stage heat exchanger 29 to a temperature below the inversion temperature. (for example
(below 20K) becomes cryogenic helium gas. When this helium gas passes through the J-T valve 30, it is brought to extremely low temperatures (e.g.
4.2 K), which becomes a two-phase gas/liquid flow and flows into the recondenser 24. Therefore, the helium gas evaporated in the inner tank 3 is liquefied again by the recondenser 24 and returned to the inner tank 3 as liquid helium. The helium gas flowing out of the recondenser 24 passes through the third stage heat exchanger 29, the second stage heat exchanger 28, the first stage heat exchanger 27, and the J-T return pipe 26, and then returns to the compressor 1.
Return to 6. FIG. 2b shows the refrigerating capacity curve of the recondenser 24 of this refrigerator 12 . The horizontal axis is the temperature T (K) of helium gas in the recondenser 24, and the vertical axis is its refrigerating capacity P-
(Watt), and indicates the operating frequency (50Hz) of the electric motor 17. FIG. 2a shows the amount of heat Q entering the liquid helium with respect to the excitation current value I. Here, Q = Q _p + Q _p , and Q _p is the amount of heat entering from the power lead 7 shown in the above formula, Q _p
is the amount of heat that enters through the superconducting coil support material (not shown) and the radiation shield plate 2, and is not present in the excitation current value and is a substantially constant value. When the excitation current value to the superconducting coil 6 is its lowest value _Inio , the amount of heat penetrating into the liquid helium 5 is _Q1 . In order to recondense all the helium evaporated in Q ₁ ,
The refrigerating capacity of the recondenser 24 is required to be P ₁ =Q ₁ , and from FIG. 2b, in this case, the refrigerator operates at a point on the refrigeration capacity curve, which is b ₁ . At this time, the temperature of the refrigerant and the temperature of the liquid helium 5 in equilibrium with the refrigerant are _T1 . Next, when the excitation current is increased and the superconducting coil 6 is operated at its maximum value _Inax , the amount of heat penetrating into the liquid helium 5 becomes _Q2 . In either case, the helium refrigerator 12 will operate at a point on the refrigerating capacity curve b ₂ in FIG. 2 b where P ₂ =Q ₂ . The temperature of liquid helium 5 at this time is _T2 . When the operation of the superconducting coil 6 is stopped and the excitation current is reduced to zero,
Q ₀ = T ₀ , the refrigerator 12 operates at the point b ₀ on the refrigeration capacity curve, and the temperature of liquid helium 5 is
It becomes T ₀ . However, the operating frequency ₁ of the electric motor 17 is constant. Now, consider the operating temperature of the superconducting coil 6. In this case, as the superconducting coil 6, for example,
Using a wound Nbti superconducting wire, the operating temperature
It is customary to design around 4.2K. The design allowable temperature margin is at most about +1K.
If the temperature is increased beyond this level, the superconducting coil 6 tends to undergo so-called quench, that is, normal conduction transition, which may lead to damage to the superconducting coil 6. In the case of Figure 2b, T ₁ is the design operating temperature (e.g.
4.2K), then T ₂ becomes T ₁ = T ₁ + 1 (for example, 5.2K)
Therefore, T ₀ becomes T ₀ < T ₁ . liquid helium 5
Since the pressure is almost atmospheric at 4.2K, liquid helium is under negative pressure at a temperature of T ₀ . That is, inside the inner tank 3 and the recondenser 24, the J-T inflow pipe 25, the J-T return pipe 26,
The J-T valve 30 is under negative pressure. Under these conditions, atmospheric moisture, nitrogen,
Impurities such as oxygen are present in the welded part of the inner tank 3 and in the recondenser 2.
The J-T piping system (J-T inflow piping 25, J-T return piping 26) is generic term). Impurities mixed into the J-T piping system will solidify at temperatures below 4.2K, so if this operating state continues for a long time, the refrigerant inlet pipe 14 and refrigerant return pipe 15 will be damaged.
The J-T piping system, which has a smaller diameter than the J-T piping system, has the disadvantage that it can become clogged with impurities, resulting in blockage of the J-T piping system, and the refrigerator 12 can no longer demonstrate its performance. In order to prevent the negative pressure phenomenon described above from occurring, it is sufficient to set T ₀ > 4.2K so that the J-T piping system and inner tank 3 are at atmospheric pressure or higher even in the non-excited state, but in this case, T ₂ <5.2K or T ₂ −T ₀
Since there is an operating temperature constraint condition of 1K, T ₀ <4.2K
Compared to the time when I _nio and I _nax can't be taken over a wide range. That is, the magnetic field variable region becomes narrow, and it may not be possible to use it, for example, in a single crystal growth apparatus or a nuclear magnetic resonance apparatus. Furthermore, each operating state shown in Fig. 2b
When the refrigerator 12 is in state nitridation at b ₀ , b ₁ , b ₂ , P
The refrigerating capacity of the refrigerator 12 has poor followability as =Q. That is, the time constant of the change in refrigerating capacity is large, for example, on the order of several hours. Therefore, when the excitation current value is changed, the time constant of the excitation current value change is sufficiently smaller than the time constant of the refrigerating capacity change of the refrigerator 12 , so the amount of heat intrusion and the refrigerating capacity are always out of balance. will operate the superconducting magnet device. For example, when the excitation current value is increased, the amount of heat entering from the outside increases immediately in proportion to the excitation current value, but the refrigerating capacity in the recondenser 24 remains almost the same as before. For this reason, the amount of evaporation of liquid helium rapidly increases, and the pressure in the sealed inner tank increases rapidly. When the internal tank pressure exceeds the design pressure, evaporated helium gas is released from a mechanical pressure relief device 10 provided in the cold storage container 4 . Since tracking of the refrigerating capacity is poor, in the worst case, all of the liquid helium 5 stored in the inner tank 3 will evaporate before the amount of heat intrusion and the refrigerating capacity are balanced and the mechanical pressure relief device 10 stops operating. and releases it into the atmosphere. Alternatively, the internal tank pressure may rise so rapidly that the rupture disk pressure relief device 11 operates and all of the liquid helium 5 is released into the atmosphere. In such a case, J
- There is a method of finding a balance point by manually changing the opening degree of the T-valve 30, but this adjustment itself is difficult and can only be done by an experienced driver. It is almost impossible for an amateur to do it. Therefore, the above-mentioned superconducting magnet device with a refrigerator has the drawback of being difficult to operate and lacking in long-term reliable operation. [Object of the Invention] The present invention has been made in order to eliminate the drawbacks of the above-mentioned prior art, and is to control the refrigerating capacity of a refrigerant refrigerator in response to a change in the amount of heat entering due to a change in the excitation current value of a superconducting coil. A superconducting magnet device that can be operated reliably over a long period of time, with no risk of contamination with impurities, the ability to select the operating current of the superconducting coil from a wide range, and the ability to always control the liquid helium temperature or pressure to a constant value, with superior operability. is intended to provide. [Summary of the Invention] In order to achieve the above object, the first invention includes a rotation speed control means for controlling the rotation speed of an electric motor for driving a compressor of a refrigerant refrigerator; In the third invention, the refrigerant refrigerator is equipped with a refrigerant flow rate control means for controlling the refrigerant discharge flow rate of the compressor, and in the third invention, the J-T piping system of the refrigerant refrigerator is equipped with a refrigerant pressure control means for controlling the refrigerant pressure. This is what I did. [Embodiments of the Invention] The present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIG. 3. The same parts as in FIG. 1 are designated by the same reference numerals and their explanation will be omitted. In order to control the rotational speed of the electric motor 17 for driving the compressor 16, it is configured as follows. An inverter variable speed control device 31 is electrically connected to the electric motor 17 . A frequency setting signal a from a central control device 32, which will be described later, is output to this inverter variable speed control device 31. The central control device 32 is configured to receive a control signal b measured by a rotation speed meter 33 of the electric motor 17 and converted into an electrical signal. The temperature of the recondenser 24 is measured by a temperature measuring device 34,
This measured value is converted into an electrical control signal c by a converter 35 and is input to the central control device 32. Further, the pressure in the inner tank 3, that is, the pressure in the pressure relief pipe 9, is measured by a pressure measuring device 36, and this measured value is converted into an electrical control signal d by a converter 37 and inputted to the central control device 32. It is becoming more and more common. Further, the excitation current value I of the external power source 8 is converted into a control signal e by a converter 40 and input to the central control device 32. The pressure relief pipe 9 is not provided with the mechanical pressure relief device 10, but instead is provided with an automatic valve 39 such as a solenoid valve or an electric valve.
The opening/closing signal f from the central control device 32 is outputted at the same time. The central control device 32 includes a control signal b based on the rotation speed of the electric motor 17, a control signal c based on the temperature of the recondenser 24, a control signal d based on the pressure of the pressure relief pipe 9, and an exciting current of the superconducting coil 6. The signal e based on is input, and the amount of heat Q intruding from the outside is determined by the excitation current signal with the content shown in Fig. 2.
Correspondingly, a frequency setting signal a to be controlled is output to the inverter variable speed control device 31, and the central control device 32 controls the automatic valve 39 by controlling as shown in FIGS. 4, 5, and 6. An open/close signal is given. Next, the operation of the superconducting magnet device of the present invention constructed as described above will be explained. The following relationship is established between the frequency of the electric motor 17 and the refrigerating capacity P of the refrigerator 12 . P=K・ ...where K: proportionality constant As shown in Figure 2b, by changing the frequency, a refrigerating capacity curve as shown can be obtained. However, in the diagram
The curve ₀ is the case when the frequency is selected so that the refrigerating capacity becomes P ₀ at T ₁ , and similarly, the curve ₁ is the case where the refrigeration capacity is P 0 at T ₁ .
The frequencies of P ₁ and ₂ are selected so that P ₂ occurs at T ₁ . Here, ₀ < ₁ < ₂ , and ₁ is the frequency when the rotational speed of the conventional electric motor 17 is not controlled. First, consider the case where the excitation current value to the superconducting coil 6 is zero. In the conventional system shown in _FIG .
Change the value to ₀ and set the refrigerator operating state to b ₄ . At this time, the central control device 32 performs control according to the flowchart shown in FIG. That is, the frequency is set to ₀ , which corresponds to zero excitation current, and the frequency is maintained at a constant value of ₀ by the rotation speed meter 33 and the inverter variable speed control device 31. When = ₀ , the fine adjustment variation Δ is added and subtracted, and = Set it to ₀ .
Let Prl be the temperature of the recondenser 24 and the temperature in equilibrium with it. Let Pro be the design allowable inner tank pressure lower than the inner tank pressure at which the rupture desk type pressure relief device 11 ruptures. Here, Pro>Prl. Operation control is performed according to the steps listed below. (1) Compare the internal tank 3 internal pressure Pr and the design allowable internal tank pressure Pro. If Pr>Pro, the automatic valve 39 is opened and the pressure is released until Pr=Prl. This opening operation number N
count. If this operation becomes frequent and exceeds N _p within a certain period of time, it is determined that the refrigerator 12 is uncontrollable and the operation of the refrigerator 12 is stopped. Pr
<If you are a Pro, proceed to the next step (2). (2) Compare Pr and Prl. If Pr=Prl, this state is maintained. When Pr<Prl, the frequency is decreased by a fine adjustment variation Δ ₀ , the refrigerating capacity is lowered, the amount of evaporated helium is increased, and the pressure in the inner tank 3 is increased. When Pr>Prl, the frequency is increased by a fine fluctuation amount Δ ₀ to increase the refrigerating capacity, increase the amount of helium gas recondensation, and lower the inner tank pressure. After these operations, compare Pr and Prl again. this
Repeat steps (1) and (2) until the characteristic curve shown in Figure 2 appears.
b Controls _{the 4} positions. Next, the superconducting coil 6 is excited so that I _nio <I<
Consider the case where the current is maintained at a value of I _nax . Hereinafter, I=for example, I _nax will be explained. In Figure 2 b, in the conventional system, the refrigerator 1 is placed at position b ₂ .
2 is being operated, but the device of the present invention does not change the frequency.
Change the operating state of the refrigerator 12 to a value of ₂ .
b Set to ₅ position. At this time, the central control device 32
performs control according to the flowchart shown in FIG. Operation control is performed in the following steps (3) and (4). (3) When setting the frequency ₂ corresponding to the required excitation current value I _nax , change the frequency as shown in FIG. In other words, in order to better follow the change in refrigerating capacity, the values of ΔF 2 _and ΔT ₂ that overshoot the frequency at a frequency of = ₂ + ΔF ₂ (ΔF ₂ : overshoot amount) for a period of ΔT ₂ are used. The optimum value is set based on the ability to follow changes in the refrigerating capacity of the refrigerating machine. After overshoot, the frequency is fixed at ₂ and constant frequency control is performed in the same way as when I=O. (4) Perform frequency control so that Pr=Pr1 as in the case of I=O. By repeating steps (3) and (4), the position _b5 on the characteristic curve shown in FIG. 2b is controlled. Next, the superconducting coil 6 is demagnetized so that I _nio <I<
Consider the case where the current is maintained at a value of I _nax . In this case, almost the same control as in the case of excitation described above is performed. However, the law of frequency change _{is 2} in Figure 5.
→ ₁ →ΔF ₁ → ₁ , and in FIG. 6, the frequencies ₂ and ΔF ₂ become ₁ and ΔF ₁ . According to the embodiment described above, since the rotation speed of the electric motor 17 that drives the compressor 16 of the refrigerator 12 can be controlled, the amount of heat intruded due to the change in the excitation current value given to the superconducting coil 6 by the external power source 8 The refrigerating capacity of the refrigerator 12 can be controlled in response to fluctuations,
Moreover, this control response is good, the refrigerating capacity follows changes in the amount of heat intrusion well, and the excitation current applied to the superconducting coil 6 can be selected from a wide range. Furthermore, since negative pressure phenomena in the J-T piping system are avoided,
- There is no contamination of impurities in the piping system near the T30 valve, there is no reduction in the capacity of the refrigerator 12 , and the operability is extremely good. In addition , since the capacity of the refrigerator 12 is controlled by controlling the rotation speed, it is possible to compensate for deterioration of the cooling capacity over time, as will be described later .
2 can be operated for a long period of time. Furthermore, the electric motor 17 is controlled by the inverter variable speed control device 31.
is controlled, the power consumed by the electric motor 17 can be kept to the minimum necessary. Therefore, overall, long-term, highly reliable operation is possible. Next, when the superconducting magnet device of the embodiment described above is operated continuously for a long period of time, the refrigerating capacity of the refrigerator 12 deteriorates over time, so a method for compensating for this will be explained. First, an example will be explained with reference to FIGS. 7 and 8. The refrigerating capacity P of the refrigerator 12 generally deteriorates over time as shown in FIG.
(t). Here, P ₀ indicates the initial refrigeration capacity, and Pf indicates the refrigeration capacity when the maintenance period of the refrigerator is reached. When designing a superconducting magnet device, it is necessary to ensure that Pf > εP ₂ . Here, ε is the safety factor, and P ₂ is the refrigeration capacity in Figure 2b. In FIG. 8, when the excitation current value I is set, the amount of heat intrusion Q is determined, and the frequency that produces the corresponding refrigerating capacity is determined. However, this frequency is a value when there is no deterioration of the refrigerating capacity over time. Since the elapsed time t ₁ from the start of operation is known, the deterioration rate η(t ₁ ) of the refrigerating capacity can be determined as P(t ₁ )/P ₀ obtained from FIG. 7. The refrigerator 12 is operated at a frequency such that the frequency increase rate K(t ₁ ) that compensates for each decrease is η(t ₁ ), thereby compensating for the deterioration of the refrigerating capacity over time.
To do this specifically, the characteristics shown in FIG. 7 are stored in the central controller 32 in advance, and the measured value of the temperature measuring device 34 or the pressure measuring device 36 shown in FIG. When a deviation occurs between the target value and the target value, the central controller 3
2 to output the frequency setting signal a to the inverter variable speed control device 31. Next, another method for compensating for the aging deterioration of the refrigerating capacity of the refrigerator 12 will be explained with reference to FIG. That is, when the exciting current value I of the superconducting coil 6 is set, the frequency corresponding to this value is determined. When operating at this frequency, if the internal pressure Pr of the inner tank 3 is lower than Prl due to deterioration of the refrigerating capacity, the frequency is increased by Δ to operate at a frequency of +Δ. The frequency is increased until Pr becomes equal to Prl to compensate for the deterioration of the refrigerating capacity over time. This compensation method is included in the flowchart of FIG. To specifically do this, the measured values of the temperature measuring device 34 or the pressure measuring device 36 shown in FIG. ,
When a deviation occurs, the inverter variable speed control device 3 is sent from the central control device 32 to compensate for this deviation.
1, the frequency setting signal a may be outputted. Next, a second embodiment of the present invention will be described with reference to FIG. Components that are the same as those in the first embodiment shown in FIG. 3 are given the same reference numerals, and their explanation will be omitted. In the first embodiment shown in FIG. 3, the rotation speed of the electric motor 17 is controlled by the inverter variable speed control device 31, but here, instead of this configuration, a configuration is adopted in which the main flow rate of the refrigerant can be controlled. be.
That is, the medium inflow pipe 14 on the discharge side of the compressor 16
includes a main flow control valve 46 and a main flow meter 47.
are installed in series. The main flow control valve 46
A bypass pipe 45 is provided between the inflow side of the compressor 16 and
is connected to the bypass pipe 45, and a bypass flow rate control valve 49 and a bypass flow rate measuring device 50 are provided in series. The flow rates measured by the main flow rate meter 47 and the bypass flow rate meter 50 are converted into electrical control signals g and h by converters 48 and 51, and are input to the central controller 32. In addition to the electrical control signals g and h mentioned above, this central control device 32 also includes a control signal c based on the temperature of the recondenser 24, a control signal d based on the pressure of the pressure relief pipe 9, and a superconducting coil 6, as shown in FIG. A signal e based on the excitation current is input, predetermined arithmetic processing is performed internally, a valve opening command is given to the main flow control valve 46 and the bypass flow control valve 49, and a valve opening command is given to the automatic valve 39. An open/close signal is given to the opening/closing signal. In the second embodiment of the present invention configured in this manner, not only can the same effects as in the first embodiment described above be obtained, but also a Since the main flow control valve 46 and the bypass flow control valve 49 are provided, the control range of the refrigerator 12 can be widened. Next, a third embodiment of the present invention will be described with reference to FIG. 11, where the same parts as in FIG. 3 are denoted by the same reference numerals and the explanation thereof will be omitted. In the embodiment shown in FIG. 3, the rotation speed of the electric motor 17 is controlled by the inverter variable speed control device 31, but instead of this structure, the J-T piping system is configured to be able to control the pressure of the medium. It is something. That is,
The J-T inflow pipe 25 and the J-T return pipe 26 are not connected to the medium inflow pipe 14 and the medium return pipe 15, but the discharge side and the inflow side of the compressor 52 are connected thereto, and the discharge side of the compressor 52 is A pressure regulating valve 54 is provided between the inlet and the inflow side. An electric motor 53 for driving the compressor 52 is directly connected to the compressor 52. Also J-
A pressure measuring device 55 is provided on the inflow side of the compressor 52 of the T return pipe 26, and the measured value measured by the pressure measuring device 55 is converted into an electrical control signal K by a converter 56 and inputted to the central control device 32. . In addition to this, the central controller 32 receives a control signal c based on the temperature of the recondenser 24, a control signal d based on the pressure of the pressure relief pipe 9, and a control signal based on the excitation current of the superconducting coil 6, as shown in FIG. e is input. Then, predetermined arithmetic processing is performed inside the central control device 32, and a valve opening signal is outputted to the pressure regulating valve 54, and an opening/closing signal is also given to the automatic valve 39. In the third embodiment of the present invention configured in this manner, not only the same effects as the first embodiment described above can be obtained, but also the J-T inflow pipe 25 and the J-T inflow pipe 25 and the J-T
Since the pressure regulating valve 54 is provided between the T-return pipe 26, the medium pressure in the J-T return pipe 26 will not fall below a certain value, that is, it will not become a negative pressure, resulting in high reliability. There are advantages. In addition, in the embodiment shown in FIG. 3 described above, the compressor 16
Although the rotation speed of the electric motor 17 that drives the motor 17 is controlled by the inverter variable speed control device 31, the rotation speed of the electric motor 17 may be controlled by a transmission such as a gear. Further, in the above-described embodiments, the Gifford-McMahon type or the Solvay type refrigerant type was taken into consideration as the refrigerant refrigerator, but similar effects can be obtained even with a reverse Stirling type refrigerant type refrigerant refrigerator. [Effects of the Invention] According to the present invention described above, the cooling capacity of the refrigerant refrigerator can be controlled in response to changes in the amount of heat intruded due to changes in the excitation current value of the superconducting coil, there is no risk of contamination with impurities, and the superconducting coil It is possible to provide a superconducting magnet device in which the operating current can be selected from a wide range, the temperature or pressure of liquid helium can always be controlled at a constant value, the operability is excellent, and long-term reliable operation is possible.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram showing an example of a conventional superconducting magnet device, Figures 2a and b are characteristic curve diagrams showing the amount of heat entering the superconducting coil with respect to the excitation current and the refrigerating capacity of the helium refrigerator. A schematic configuration diagram showing the first embodiment of the superconducting magnet device of the present invention, FIG. 4 is a flow chart showing the operation control method of the superconducting magnet device when the excitation current is zero, and FIG. Diagram showing the frequency change of the electric motor, No. 6
The figure is a flowchart showing a method for controlling the operation of a superconducting magnet device when changing the excitation current, Figure 7 is a diagram showing the deterioration of the refrigerating capacity over time, and Figures 8 and 9 are a diagram showing the method of compensating for the deterioration of the refrigerating capacity over time. The flowchart shown, FIG. 10, and FIG. 11 are schematic configuration diagrams showing second and third embodiments of the superconducting magnet device of the present invention. 1...Outer tank, 2...Radiation shield plate, 3...Inner tank, 4 ...Cool container, 5...Liquid helium, 6...
...Superconducting coil, 7... Power lead, 8... External power source, 9... Pressure relief piping, 10... Mechanical pressure relief device, 11... Lapture desk pressure relief device, 12
... Helium refrigerator, 13 ... Refrigerator head, 1
4... Refrigerant inflow pipe, 15... Refrigerant return pipe, 1
6... Compressor, 17... Electric motor, 18... First stage cooler, 19... Second stage cooler, 20... First stage station, 21... Heat transfer member, 22... Second stage cooler
Stage station, 23...Heat transfer member, 24...Recondenser, 25...J-T inflow pipe, 26...J-
T return pipe, 27...1st stage heat exchanger, 26...
Second stage heat exchanger, 29...Third stage heat exchanger, 30
...J-T valve, 31... Inverter variable speed control device, 32... Central control device, 35, 37, 40...
...Converter, 34...Temperature measuring device, 36...Pressure measuring device, 39...Automatic valve, 45...Bypass piping,
46...Main flow control valve, 47...Main flow measuring device,
48, 51, 56...Converter, 49...Bypass flow rate control valve, 50...Bypass flow rate measuring device, 52
... Compressor, 53 ... Electric motor, 54 ... Pressure control valve, 55 ... Pressure measuring device.

Claims (1)

[Scope of Claims] 1. An inner tank that encloses liquid helium and houses a superconducting coil, an outer tank that houses this inner tank, and a radiation shield disposed between this outer tank and the inner tank. a cold container that maintains the superconducting coil at an extremely low temperature, a power lead that electrically connects the superconducting coil to an external power source installed outside the cold container, and a liquid helium container in the inner tank. A recondenser for recondensing evaporated gas, and a J-T piping system installed such that one end thereof is connected to the refrigerant inflow side and the refrigerant return side of the recondenser, and the other end is located outside the cold storage container. A plurality of coolers that cool the power lead, the radiation shield, and the J-T piping system; A piping system that supplies refrigerant to the power lead, the radiation shield, and the J-T piping system; and the outside of the cold storage container. a refrigerant refrigerator that is arranged in a refrigerant refrigerator and includes a compressor that compresses the refrigerant and an electric motor that drives the compressor; a rotation speed control means that controls the rotation speed of the electric motor of the refrigerant refrigerator; and a rotation speed of the electric motor. A control signal b based on the temperature of the recondenser, a control signal c based on the temperature of the recondenser, a control signal d based on the pressure of the pressure relief piping that releases the pressure in the inner tank, and a control signal e based on the excitation current of the superconducting coil are input. an automatic valve that determines the amount of heat intruding from the outside based on the excitation current signal, outputs a frequency setting signal a to be controlled correspondingly to the rotation speed control means, and is provided in the pressure relief pipe. A superconducting magnet device, comprising: a central control device that gives an open/close signal f to the refrigerant refrigerator, and the refrigerating capacity of the refrigerant refrigerator can be controlled with respect to the amount of heat entering from the outside of the cold storage container. 2 Consisting of an inner tank that encloses liquid helium and houses a superconducting coil, an outer tank that houses this inner tank, and a radiation shield placed between this outer tank and the above-mentioned inner tank, A cold storage container that maintains the coil at an extremely low temperature; a power lead that electrically connects the superconducting coil to an external power source installed outside the cold storage container; and a power lead that recondenses the evaporated gas of the liquid helium in the inner tank. a recondenser; a J-T piping system with one end connected to the refrigerant inflow side and the refrigerant return side of the recondenser and the other end located outside the cold storage container; the power lead; a plurality of coolers that cool the radiation shield body and the J-T piping system; a piping system that supplies refrigerant to the power lead, the radiation shield body, and the J-T piping system; a refrigerant refrigerator comprising a compressor that compresses the refrigerant and an electric motor that drives the compressor, a rotation speed control means that controls the rotation speed of the electric motor of the refrigerant refrigerator, and a temperature measurement device that measures the temperature of the recondenser. a pressure measuring means for measuring the pressure of the pressure relief piping; inputting a temperature measurement value measured by the temperature measurement means or a pressure measurement value measured by the pressure measurement means and a set value; When a deviation occurs in
and a central control device that outputs a frequency setting signal to the rotation speed control means to compensate for this deviation, and the refrigerant refrigerator is provided with a function to compensate for deterioration of the refrigerating capacity over time. Characteristic superconducting magnet device. 3 Consists of an inner tank filled with liquid helium and housing a superconducting coil, an outer tank housing this inner tank, and a radiation shielding body disposed between this outer tank and the above-mentioned inner tank, and the above-mentioned superconducting A cold storage container that maintains the coil at an extremely low temperature; a power lead that electrically connects the superconducting coil to an external power source installed outside the cold storage container; and a power lead that recondenses the evaporated gas of the liquid helium in the inner tank. a recondenser; a J-T piping system with one end connected to the refrigerant inflow side and the refrigerant return side of the recondenser and the other end located outside the cold storage container; the power lead; a plurality of coolers that cool the radiation shield body and the J-T piping system; a piping system that supplies refrigerant to the power lead, the radiation shield body, and the J-T piping system; A refrigerant refrigerator consists of a compressor that compresses the air and an electric motor that drives the compressor, and the main flow rate of the refrigerant provided in the refrigerant inflow pipe installed between the refrigerant refrigerator and the J-T piping system. a flow rate control valve to be adjusted; a bypass flow rate control valve provided in a bypass pipe line connected to an inlet side and a discharge side of the refrigerant refrigerator; and electrical control according to the flow rate of the bypass line and the refrigerant inflow pipe. Signals g and h, a control signal c based on the temperature of the recondenser, a control signal d based on the pressure of the pressure relief piping that releases the pressure in the inner tank, and a control signal e based on the excitation current of the superconducting coil are input. Internally, through predetermined calculation processing, it gives valve opening commands i, j to the flow rate control valve and the bypass flow rate control valve, and also gives open/close signals to the automatic valve installed in the pressure relief pipe. A superconducting magnet device, comprising: a central control device that gives f, and the refrigerating capacity of the refrigerant refrigerator can be controlled with respect to the amount of heat entering from the outside of the cold storage container. 4 Consists of an inner tank filled with liquid helium and housing a superconducting coil, an outer tank housing this inner tank, and a radiation shielding body disposed between this outer tank and the above-mentioned inner tank, A cold storage container that maintains the coil at an extremely low temperature; a power lead that electrically connects the superconducting coil to an external power source installed outside the cold storage container; and a power lead that recondenses the evaporated gas of the liquid helium in the inner tank. a recondenser; a J-T piping system with one end connected to the refrigerant inflow side and the refrigerant return side of the recondenser and the other end located outside the cold storage container; the power lead; a plurality of coolers that cool the radiation shield body and the J-T piping system; a piping system that supplies refrigerant to the power lead, the radiation shield body, and the J-T piping system; A refrigerant refrigerator consists of a compressor that compresses the air and an electric motor that drives the compressor, and the main flow rate of the refrigerant provided in the refrigerant inflow pipe installed between the refrigerant refrigerator and the J-T piping system. a bypass flow control valve provided in a bypass piping line connected to an inlet side and a discharge side of the refrigerant chiller; a temperature measuring means for measuring the temperature of the recondenser; A pressure measurement means for measuring the pressure of pressure piping, and a temperature measurement value measured by the above-mentioned temperature measurement means or a pressure measurement value measured by the above-mentioned pressure measurement means and a set value are input, and a deviation occurs between the two. When,
and a central control device that outputs a frequency setting signal to the rotation speed control means to compensate for this deviation, and the refrigerant refrigerator is provided with a function to compensate for deterioration of the refrigerating capacity over time. Characteristic superconducting magnet device. 5 Comprising an inner tank filled with liquid helium and housing a superconducting coil, an outer tank housing this inner tank, and a radiation shielding body disposed between this outer tank and the above-mentioned inner tank, the above-mentioned superconducting A cold storage container that maintains the coil at an extremely low temperature; a power lead that electrically connects the superconducting coil to an external power source installed outside the cold storage container; and a power lead that recondenses the evaporated gas of the liquid helium in the inner tank. a recondenser; a J-T piping system with one end connected to the refrigerant inflow side and the refrigerant return side of the recondenser and the other end located outside the cold storage container; the power lead; a plurality of coolers that cool the radiation shield body and the J-T piping system; a piping system that supplies refrigerant to the power lead, the radiation shield body, and the J-T piping system; A refrigerant refrigerator consists of a compressor that compresses the air and an electric motor that drives the compressor, and the main flow rate of the refrigerant provided in the refrigerant inflow pipe installed between the refrigerant refrigerator and the J-T piping system. a flow control valve to be adjusted; a pressure control valve provided in a J-T piping system connected to the inlet side and discharge side of the refrigerant refrigerator; and a control signal k according to the pressure on the inlet side of the refrigerant refrigerator. Then, a control signal c based on the temperature of the recondenser, a control signal d based on the pressure of the pressure relief pipe that releases the pressure in the inner tank, and a control signal e based on the excitation current of the superconducting coil are input, and the internal a central control device that gives a valve opening command to the pressure regulating valve through predetermined calculation processing and gives an open/close signal f to the automatic valve provided in the pressure relief piping, A superconducting magnet device characterized in that the refrigerating capacity of a refrigerator can be controlled with respect to the amount of heat entering from the outside of a cold storage container. 6 Consisting of an inner tank filled with liquid helium and housing a superconducting coil, an outer tank housing this inner tank, and a radiation shield placed between this outer tank and the above-mentioned inner tank, the above-mentioned superconducting A cold storage container that maintains the coil at an extremely low temperature; a power lead that electrically connects the superconducting coil to an external power source installed outside the cold storage container; and a power lead that recondenses the evaporated gas of the liquid helium in the inner tank. a recondenser; a J-T piping system with one end connected to the refrigerant inflow side and the refrigerant return side of the recondenser and the other end located outside the cold storage container; the power lead; a plurality of coolers that cool the radiation shield body and the J-T piping system; a piping system that supplies refrigerant to the power lead, the radiation shield body, and the J-T piping system; A refrigerant refrigerator consists of a compressor that compresses the air and an electric motor that drives the compressor, and the main flow rate of the refrigerant provided in the refrigerant inflow pipe installed between the refrigerant refrigerator and the J-T piping system. a pressure regulating valve provided in a J-T piping system connected to an inlet side and a discharge side of the refrigerant refrigerator; a temperature measuring means for measuring the temperature of the recondenser; A pressure measurement means for measuring the pressure of the pressure relief piping, and a temperature measurement value measured by the above-mentioned temperature measurement means or a pressure measurement value measured by the above-mentioned pressure measurement means and a set value are input, and a deviation occurs between the two. When
and a central control device that outputs a frequency setting signal to the rotation speed control means to compensate for this deviation, and the refrigerant refrigerator is provided with a function to compensate for deterioration of the refrigerating capacity over time. Characteristic superconducting magnet device.