JP5518965B2 - Excitation power source for superconducting magnets - Google Patents

Description

  The present invention relates to an excitation power source for a superconducting magnet.

  In superconducting magnets, the superconducting state of quenching is fluctuated, and zero resistance is normally conducted and voltage is generated. is there. Conversely, if the current changes suddenly due to a problem with the excitation power supply itself, the above-mentioned quench occurs, which affects each other. On the excitation power source side, the power element may be damaged due to the reverse flow of high voltage or large energy that has lost its place of travel. On the superconducting magnet side, quenching occurs due to a sudden change in current, which may damage the superconducting magnet. There is.

  Therefore, it is safe to disconnect the mutual relationship (connection) when any abnormality of the exciting power supply and the superconducting magnet is detected. However, it is dangerous to break (cut off) the mutual relationship (connection) when a large current flows. Here, in the technique described in Patent Document 1, a contrivance is made such as arranging a capacitor in parallel with the circuit breaker.

JP 7-177648 A

  However, a protection method that interrupts a contact point that is energized is not suitable for controlling a large current. In the protection method in the control of a large current, generally, a method is adopted in which both ends of the output of the excitation power supply are short-circuited so that the excitation power supply and the superconducting coil are substantially separated.

  Here, the method of short-circuiting both ends of the output of the excitation power supply has a drawback. For example, if the superconducting coil is not actually quenched but is short-circuited due to a false detection (if it malfunctions), a combination of a small resistance (R) and superconducting coil (L) will result in the release of stored energy Takes a long time, and the short circuit at both ends of the output cannot be released for a long time.

  Further, as an abnormality (trouble) from the excitation power source side, there is an abnormality called overheating in which the power element is heated. When the used sequencer or microcomputer detects an instantaneous drop in the main power supply, the current output is stopped as an internal abnormality. If both ends of the excitation power supply output are short-circuited at this time, the LR discharge takes a long time. Similarly, the output short circuit cannot be released. Even if UPS is used as a measure against instantaneous voltage drop, there are restrictions on the backup time and the range that can be backed up, and it can hold only 10 minutes, or it can hold only the control system, but it can not back up to the power system, etc. Again, it is necessary to protect the magnet by short-circuiting both ends of the excitation power supply at any timing, and there is a problem that it is difficult to return to the normal state.

  Further, for example, when the fuse in the excitation power source is blown out, the replacement of the fuse itself is completed by replacing the fuse. However, as described above, it takes a long time to return the unquenched superconducting magnet from the protected state to the normal state.

  On the other hand, from the viewpoint of preventing damage to the excitation power source and the superconducting magnet, it is desirable to raise the level of detection of abnormal conditions such as quenching. In addition, it is desirable that the instantaneous drop can be detected with high sensitivity from the viewpoint of preventing malfunction of the sequencer and the microcomputer. However, increasing the abnormal state detection level increases the frequency of malfunctions (tradeoff problem).

  The present invention has been made in view of the above circumstances, and its purpose is that an abnormal state such as quench, internal abnormality, or instantaneous power supply voltage drop is erroneously detected and both ends of the output of the excitation power supply are short-circuited. Then, it is providing the excitation power supply for superconducting magnets which can be returned to a normal state (state which is not short-circuited) rapidly after that.

  To achieve the above object, the present invention provides an exciting power source for exciting a superconducting magnet comprising a superconducting coil, the power source, a power unit connected to the power source, the power source, the power unit, or the superconducting power source. Provided in a loop that includes a protection means that closes a contact that short-circuits both ends of the output of the power unit and protects it when a magnet abnormality is detected, the superconducting coil, and the contact. A first current detector that detects a current value, wherein the power unit includes an amplifier, a second current detector that detects an output current value of the power unit, and a current control unit that controls the output current value; And when the contact is closed by the protection means, the output value is detected using the detection values of the first current detector and the second current detector. Providing excitation power supply for the superconducting magnet has a return means for returning from protection state to open the contact mixture was allowed to coincide with the current flowing through the superconducting coil and the current value.

  According to this configuration, the contact point is opened by opening the contact point after matching the output current value of the power unit with the current value flowing through the superconducting coil using the detection values of the first current detector and the second current detector. A sudden change in current after opening can be prevented. Thereby, quenching of the superconducting coil can be prevented. That is, according to the present invention, even if an abnormal state is erroneously detected and both ends of the output of the excitation power supply are short-circuited, the contact point is opened after matching the output current value of the power unit and the current value flowing through the superconducting coil. Thus, it is possible to quickly return to the normal state (the state where the short circuit is not short-circuited).

  Further, according to the present invention, it is possible to quickly return to the normal state (the state in which the short circuit is not short-circuited). Therefore, even if a malfunction occurs more frequently by raising the abnormal state detection level such as quenching, No time is required to return to the state. In other words, even if the abnormal state detection level such as quenching is increased, there is no trouble (there is no trouble in returning to the normal state), and the abnormal state detection level is increased to make the contact operate relatively sensitively. This can prevent damage to the excitation power source and superconducting magnet.

  In the above-mentioned “opening the contact after matching the output current value of the power unit and the current value flowing through the superconducting coil”, “match” does not mean only perfect match but almost match. That means. That is, there may be a slight difference between the output current value of the power unit and the current value flowing through the superconducting coil. It is only necessary to match the output current value of the power unit and the current value flowing through the superconducting coil to such an extent that the sudden change of the current value flowing through the superconducting coil after opening the contact can be prevented and quenching of the superconducting coil can be prevented. is there.

  In the present invention, when the return button is pressed, the return means reads the detected value of the first current detector as a target value, sets the detected value of the second current detector as a current value, and a predetermined sweep rate. It is also possible that the contact point is opened after both detection values are matched.

  According to this configuration, it is possible to suppress damage to the power unit when returning from the protection state to the normal state by matching both detection values with a predetermined sweep plate.

  Further, in the present invention, the first current detector is provided at a position where the output current value can be detected in the loop, and the current control means normally uses the detection value of the first current detector. The output current value is controlled and the output current value is controlled by using the detection value of the second current detector when returning from the protection state, thereby controlling the output current at the normal time and the return time. The current detectors may be switched.

  The output current control at the time of return from the protection state may be relatively rougher than the normal output current control. That is, according to this configuration, the second current detector can be a current detector with rough accuracy, and the parts cost of the excitation power source can be reduced.

  Furthermore, in the present invention, the power unit includes a plurality of power units, the first current detector is a current detector that detects an output current value of the entire excitation power source, and the second current detector is provided in each power unit. A current detector for detecting an output current value of the power unit, and outputting a current command value so that a detection value of the first current detector is equal to a set output current value of the entire excitation power source And command value distribution means for distributing the current command value output from the main control means to each power unit, wherein the current control means provided in each power unit is a detection value of the second current detector. However, the output current value of each power unit may be controlled to be equal to the current command value distributed from the command value distribution means.

  According to this configuration, if a component failure occurs in an amplifier in a power unit among a plurality of power units and the power unit is unable to flow a fixed current, a current command that compensates for it from the main control means A value is emitted. Further, the current command value is distributed to each power unit by the command value distribution means. And since each output current value is controlled so that the current control means of each power unit becomes equal to the current command value distributed by the command value distribution means, the current does not extremely drift to the normal power unit, and the current drifts as a whole. The phenomenon can be prevented.

  In the present invention, the first current detector is in a position in series with the contact, and the output loop of the power unit and the loop on the superconducting coil side when the contact is closed are common. The return means is provided in a portion, and when the return button is pushed, the detection value of the first current detector is set to the current value, and the target value of the first current detector is set to zero, and the power unit portion is set to a predetermined value. The contact point may be opened after the detection value of the first current detector is made equal to zero by controlling with the sweep plate.

  According to this configuration, by causing the detection value of the first current detector to match zero with a predetermined sweep plate, it is possible to suppress damage to the power unit when returning from the protection state to the normal state.

  In the above-described “opening the contact after matching the detection value of the first current detector to zero”, “match” does not mean only a perfect match to the zero value, but almost zero. It means that it is a value. That is, it may not be completely zero. The detection value of the first current detector may be made equal to zero to the extent that a sudden change in the current value flowing through the superconducting coil after opening the contact can be prevented and quenching of the superconducting coil can be prevented.

  In the present invention, the first current detector is in a position in series with the contact, and the output loop of the power unit and the loop on the superconducting coil side when the contact is closed are common. When the return button is pressed, the return means sets the power unit portion to a predetermined value using a value obtained by adding the detection value of the first current detector and the detection value of the second current detector as a target value. The contact point may be opened after the detection value of the second current detector is matched with the target value under the control of the sweep plate. In this case, it is preferable that the detection value of the first current detector and the detection value of the second current detector are sequentially added repeatedly to sequentially update the target value.

  According to this configuration, since the control of the power unit is the same as the normal sweep control, the control is easy to perform. Note that “matching” here does not mean only perfect matching, but includes being substantially matched.

  According to the second aspect of the present invention, there is provided an exciting power source for exciting a superconducting magnet having a superconducting coil, the power source, a power unit connected to the power source, the power source, the power unit, Or when the abnormality of the superconducting magnet is erroneously detected, when the contact that closes the both ends of the output of the power unit to make it in a protected state and the contact is closed by the protection means, Storage means for storing the output current value of the power unit immediately before, the power unit comprising an amplifier, a current detector for detecting the output current value of the power unit, and current control means for controlling the output current value. And when the contact is closed by the protection means, the detected value of the current detector and the stored value of the storage means Providing excitation power supply for the superconducting magnet has a return means for returning from protection state to open the contact mixture was allowed to coincide with the current flowing through the superconducting coil and the output current value by using.

  According to this configuration, only one current detector is required. If it is assumed that a microcomputer is originally used for the control, calculation and storage can be handled by a microcomputer program (software), so there is an advantage that a current detector as a hardware component can be omitted.

  Further, in the present invention, a timer for measuring an elapsed time from the time when the storage means stores the output current value, an elapsed time measured by the timer, and a correction value per time stored in advance. Correction means for correcting a stored value, and the return means is a detection value of the current detector and a storage value of the storage means corrected by the correction means when the contact is closed by the protection means. After the output current value and the current value flowing through the superconducting coil are matched with each other, the contact may be opened.

  According to this configuration, not only the storage unit but also the timer and the correction unit are further provided, so that the protected state can be restored more reliably.

  According to the present invention, when the contact is closed by the protection means, the output current value of the power unit and the current value flowing through the superconducting coil are matched, and then the contact is opened to return from the protection state. Even if erroneous detection is performed and both ends of the output of the excitation power supply are short-circuited, it is possible to quickly return to the normal state (the state where the short-circuit is not short-circuited).

It is a block diagram which shows the excitation power supply which concerns on 1st Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of the return from a protection state. It is a block diagram which shows the excitation power supply which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the excitation power supply which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the excitation power supply which concerns on 4th Embodiment of this invention. It is a block diagram which shows the excitation power supply which concerns on 5th Embodiment of this invention. It is a block diagram which shows the excitation power supply which concerns on 6th Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram showing an excitation power source 101 according to the first embodiment of the present invention.

(Configuration of excitation power supply 101)
The excitation power source 101 is a power source for exciting the superconducting magnet 2 including the superconducting coil 2L, and is connected to the superconducting coil 2L. Superconducting coil 2L is formed by winding a superconducting wire.

  As shown in FIG. 1, the excitation power supply 101 includes a power supply 1, a power unit 3, a first shunt resistor 5 (first current detector), and a protection circuit 16 (protection means).

(Power supply)
The power source 1 includes a transformer (not shown) connected to an AC power source, a transistor circuit (not shown) that supplies a DC current that is obtained by rectifying and smoothing the AC power of the transformer to the superconducting coil 2L. For the power supply 1, a commercially available switching regulator or the like may be used.

(First current detector)
As the current detector (first current detector), not a shunt resistor but a non-contact type current detector that detects a magnetic field generated by a current by a Hall element may be used (about a second shunt resistor 8 described later). The same). The first shunt resistor 5 can detect the current value in the loop A including the superconducting coil 2L and the contact 4a of the protection relay 4 (and can detect the output current value of the power unit 3 when the contact 4a is open). (Position in the loop A).

(Power unit)
A power unit 3 is connected to the power source 1. The power unit 3 includes a transistor 7 (usually a plurality of transistors) that is an amplifier, and a second shunt resistor 8 (second current detector) that can detect the output current value of the power unit 3 even in a protected state (contact 4a is closed). ), A current control circuit 9 (current control means) for controlling the output current value of the power unit 3, a current command circuit 10 (current command means) for commanding the current value to the current control circuit 9, and a sweep for the current command circuit 10 A sweep rate setting device 33 for instructing a rate, a return circuit 31 (return means) for returning from the protected state in cooperation with the current command circuit 10, and a return button 32 for instructing the return circuit 31 to return (start return control) And. Note that the sweep plate setting device 33, the return circuit 31, and the return button 32 are not necessarily regarded as components of the power unit 3, that is, they may be regarded as components different from the power unit 3.

(amplifier)
Although a general bipolar transistor is used as the transistor 7, each power element such as a field effect transistor (FET), IGBT, or MOSFET may be used (the same applies to the transistor 17 described later).

(Returning from the protected state)
The return circuit 31 cooperates with the current control circuit 9 to use the detected values of the first shunt resistor 5 and the second shunt resistor 8 when the contact 4a is closed by the protection circuit 16 (during the return control). After the output current value of 3 and the current value flowing through the superconducting coil 2L are matched, the contact 4a is opened to return from the protected state (the state where both ends of the output of the power unit 3 are short-circuited) (The circuit is assembled). That is, after the contact 4a is closed by the protection circuit 16, the return circuit 31 is pressed against the protection relay 4 when the return button 32 is pressed and the output current value of the power unit 3 matches the current value flowing through the superconducting coil 2L. A signal is sent to open the contact 4a.

  In the above-mentioned “opening the contact 4a after matching the output current value of the power unit 3 and the current value flowing through the superconducting coil 2L”, “match” does not mean only perfect match, but almost one. Say what you do. That is, there may be a slight difference between the output current value of the power unit 3 and the current value flowing through the superconducting coil 2L. The output current value of the power unit 3 and the current value flowing through the superconducting coil 2L coincide with each other to prevent sudden change of the current value flowing through the superconducting coil 2L after the contact 4a is opened and to prevent quenching of the superconducting coil 2L. You can do that.

  Further, the current control circuit 9 and the return circuit 31 may not be configured separately as in the present embodiment, but may be configured as one circuit.

  Furthermore, in this embodiment, the current control means, the return means, and the protection means have a circuit configuration. However, a controller that performs program control using a microcomputer (microcomputer) or the like is adopted, and control is performed by the controller. Also good. In this case, since there is a degree of freedom in program setting, it is easy to change the setting (the same applies to a current command circuit 10, a current control circuit (19, 29), a distributor 14, and a main control circuit 12 described later).

  As will be described in detail later, the return circuit 31 is not incorporated in the excitation power supply 101, the first shunt resistor 5 is used as a mere current display detector, and the operator (person) manually controls the return circuit 31. May be.

(Current command means)
The current command circuit 10 normally supplies a current to the current control circuit 9 such as gradually increasing the command current according to the amount of increase determined by the sweep plate setting unit 33 during excitation for increasing the current, for example, by an operation switch (not shown). It is configured to command (output) a value. The current control circuit 9 is configured to control the output current value of the power unit 3 based on the current command value output from the current command circuit 10 and the detected value of the second shunt resistor 8. Here, the normal time means a state where the contact 4a is open (a state where the contact 4a is not short-circuited).

  Further, the return circuit 31 sets the current value to the current control circuit 9 in cooperation with the current command circuit 10 with the detection value (current detection value) of the first shunt resistor 5 as a target value when returning from the protection state. It is configured to output. The return circuit 31 cooperates with the current control circuit 9 to read the detected value of the first shunt resistor 5 as a target value, and after matching the target value with the detected value of the second shunt resistor 8, the contact 4a is connected. (The detection value of the second shunt resistor 8 is used to control the output current value of the power unit 3. The detection value of the first shunt resistor 5 is used as a target value). Here, the protection state means a state where the contact 4a is closed (a state where the contact 4a is short-circuited). Returning refers to a process of shifting from a closed state to an open state.

  Generally, in current feedback control using a current shunt, control is performed by applying feedback to the commanded current. Therefore, basically, when a command is issued, the output current is adjusted to the command current in real time. The description so far has been made to match the detected value of the second shunt resistor 8 for the sake of clarity, but as an actual method, the output value of the current command circuit 10 is set to the first shunt resistor 5 which is the target value. Since the current control circuit 9 adjusts the second shunt resistor 8 and this command value immediately after adjustment, the “detected value of the second shunt resistor 8” is “the output command of the current command circuit 10”. The value is read as “value”. Note that, as in the first description, a method of actually confirming the match using the detection value of the second shunt resistor 8 may be used.

  The protection circuit 16 (protection means) is also supplied with an internal abnormality signal 100 such as an instantaneous voltage drop or power failure generated from a controller (not shown) using the microcomputer.

(Protection relay)
The protection relay 4 includes a contact 4a. The contact 4a is incorporated at a position where both ends of the output of the power unit 3 are short-circuited. In other words, the superconducting coil 2L is incorporated at a position where both ends are short-circuited. The contact 4a of the protection relay 4 may be composed of an A contact or a B contact. When the contact 4a of the protection relay 4 is configured as an A contact, the contact 4a is closed when the electrical signal is turned on, and the contact 4a is opened when the electrical signal is turned off. When the contact 4a of the protection relay 4 is configured as a B contact, the contact 4a is closed when the electrical signal is turned off, and the contact 4a is opened when the electrical signal is turned on. That is, the B contact is closed by the restoring force of the spring when power is not supplied to the relay (protection relay 4), and is opened by electromagnetic force when power is supplied to the relay (protection relay 4). An electrical contact that is in a state.

  In consideration of a power failure (a state in which power is not supplied to the relay (protection relay 4)), the contact 4a of the protection relay 4 is preferably configured as a B contact (normally closed) (the same applies to the embodiments described later). ). If the contact 4a is configured as a B contact, even if the return circuit 31 (return means) does not operate due to a power failure, the contact 4a is closed and both ends of the output are short-circuited. Thereby, the electric current which flows into the superconducting coil 2L which is not quenched can be recirculated through the contact 4a. Thereafter, when the original power supply is restored, the return state can be returned from the protected state to the normal state by the operation of the return circuit 31 (return means). On the other hand, when the contact 4a is configured as the A contact, the return circuit 31 operates for a short time after the power failure. However, when the power failure becomes longer, the return circuit 31 does not operate and the contact 4a opens. As a result, the current flowing through the superconducting coil 2L that has not been quenched cannot be recirculated.

  Here, the protection circuit 16 is an overvoltage detection circuit. For example, if the set value of the excitation voltage of the superconducting coil 2L is 10V, a signal is output to the protection relay 4 and the current command circuit 10 as an overvoltage (abnormal) when the excitation voltage exceeds 12V. There are various protection circuits, and the protection circuit is not limited to the overvoltage detection circuit.

  Here, when receiving a signal from the protection circuit 16, the current command circuit 10 is configured to command the current control circuit 9 so that the output current of the power unit 3 becomes zero. Further, the protection relay 4 is configured to close the contact 4 a when receiving a signal from the protection circuit 16.

  In the present embodiment, an example is shown in which the protection circuit 16 is incorporated in the excitation power source 101 and abnormality of the superconducting magnet 2 is detected. However, a circuit (means) for detecting abnormality of the power source 1 and the power unit 3 is incorporated in the excitation power source 101. Further, quench detection information may be added to this circuit, and a signal may be output from the circuit to the protection relay 4 and the current command circuit 10. The circuit for detecting an abnormality in the power source 1 or the power unit 3 is a circuit configured to detect, for example, overheating, overcurrent, power source voltage drop, and power failure of the power source 1 or power unit 3.

(Return control from the protection state by the excitation power supply)
Next, return control from the protected state will be described. FIG. 2 is a flowchart showing the operation at the time of return from the protected state.

  When the abnormality of the superconducting magnet 2 is detected by the protection circuit 16, the contact 4a is closed by the protection circuit 16 via the protection relay 4, and the output current of the power unit 3 is made zero by the current control circuit 9. At this time, the current flowing through the superconducting coil 2L flows through the loop A including the superconducting coil 2L and the contact 4a of the protective relay 4 as indicated by IA in FIG. On the other hand, the current IB flowing from the transistor 7 of the power unit 3 becomes zero. The same applies when an abnormality of the power source 1 or the power unit 3 is detected.

  Here, when the superconducting coil 2L is quenched, the superconducting coil 2L becomes normal conducting and has resistance, so that IA attenuates quickly. However, the protection circuit 16 may malfunction due to noise or the like. Moreover, even if a voltage is applied to the superconducting coil 2L for a moment, the superconducting coil 2L may return to the superconducting state thereafter. In addition, the protection circuit 16 may operate when the power source voltage drops slightly. In such a case, since the superconducting coil 2L is in a superconducting state, the resistance of the loop A is extremely small, and it may take about one day for the current IA to become zero. If the contact 4a is opened, the current IA can be reduced to zero, but then the superconducting coil 2L is quenched. Forcibly quenching leads to damage to the superconducting coil 2L.

  Here, in the excitation power source 101, control is performed as shown in the flow in FIG. When the return button 32 is pressed (S1, an abbreviation for Step 1), the current command circuit 10 sets the detected value (current value) of the first shunt resistor 5 as a target value and the current value to the current control circuit 9. Is output. The current control circuit 9 reads the detection value (current value) of the first shunt resistor 5 as a target value (S2). Then, the current control circuit 9 sets the read target value of the first shunt resistor 5 as a set value (S3). Further, the current control circuit 9 reads a predetermined sweep plate value or a sweep plate value from the sweep plate setting unit 33 via the current command circuit 10 (S4). Then, the current command circuit 10 causes the current control circuit 9 to send the current command value to the current control circuit 9 with a predetermined sweep rate so that the detected value of the second shunt resistor 8 (the output current value of the power unit 3) matches the set value. (S5). S2 to S5 are repeated until IA and IB match. When IA = IB is confirmed (if IA = IB), the return circuit 31 issues a signal to the protective relay 4 to open the contact 4a, and the contact 4a is opened (S7). Note that IA = IB may be a case where IB is actually a detected value of the second shunt resistor 8 or a current command value from the current command circuit 10 to the current control circuit 9 may be IB. Further, in this flow, the value of the first shunt resistor 5 is taken every time in S2, but since the processing time is short and the coil current (IA) decaying during that time is small, the S2 step is performed only once. Thereafter, S3 to S6 may be repeated.

(Second Embodiment)
FIG. 3 is a configuration diagram showing an excitation power source 201 according to the second embodiment of the present invention. The difference from the first embodiment is the position of the first shunt resistor (first current detector). In the present embodiment, the first shunt resistor 5 is positioned in parallel with the superconducting coil 2L. Thus, the 1st shunt resistance 5 should just be provided in the position which can detect the electric current IA which flows into the superconducting coil 2L, when the contact 4a of the protection relay 4 closes. In other words, the first shunt resistor 5 is located in series with the contact 4a and is common to the loop B of the output of the power unit 3 and the loop A on the superconducting coil 2L side when the contact 4a is closed. It is provided in the part.

  In the present embodiment, the current control circuit 9 increases the output current value of the power unit 3 with a predetermined sweep rate so that the detection value (current detection value) of the first shunt resistor 5 becomes zero. The detection value of the first shunt resistor 5 being zero means that IA and IB flowing in opposite directions coincide with each other. When IA = IB is confirmed (if IA = IB), the current control circuit 9 issues a signal to the protective relay 4 to open the contact 4a, and the contact 4a is opened.

  As a modification, when the return button 32 is pressed, a value obtained by adding the detection value of the first shunt resistor 5 and the detection value of the second shunt resistor 8 is used as a target value, and the second shunt resistor is used with a predetermined sweep plate. Alternatively, the contact point 4a may be opened after the detected value 8 matches the target value. Here, it is preferable that the target value is sequentially updated by repeatedly adding the detected value of the first shunt resistor 5 and the detected value of the second shunt resistor 8 sequentially. Since IA is a current larger than IB flowing in the direction opposite to IB, the detected value of the first shunt resistor 5 is “IA−IB”. The detected value of the second shunt resistor 8 is “IB”. Therefore, the value obtained by adding the detection value of the first shunt resistor 5 and the detection value of the second shunt resistor 8 is “IA”.

  As a further modification, as a combination of the above-described controls, when the return button 32 is pressed, the detection value of the first shunt resistor 5 is controlled to zero with a predetermined sweep plate, and the predetermined sweep plate is used. Control is performed so that the detection value of the second shunt resistor 8 matches the value obtained by adding the detection value of the first shunt resistor 5 and the detection value of the second shunt resistor 8. Then, the detection value of the first shunt resistor 5 matches zero, and the detection value of the second shunt resistor 8 matches the value obtained by adding the detection value of the first shunt resistor 5 and the detection value of the second shunt resistor 8. Control is performed so as to open the contact 4a at the earlier stage. By configuring the excitation power supply in this way, it is possible to return to the normal state (the state where it is not short-circuited) more quickly.

  As described above, according to the present invention, the contact value 4a is obtained after matching the output current value of the power unit 3 with the current value flowing through the superconducting coil 2L using the detected values of the first shunt resistor 5 and the second shunt resistor 8. Opening can prevent a sudden change in current after the contact 4a is opened. Thereby, quenching of the superconducting coil 2L can be prevented. That is, according to the present invention, even if an abnormal state is erroneously detected and both ends of the output of the excitation power supply (power unit 3) are short-circuited, the output current value of the power unit 3 and the current value flowing through the superconducting coil 2L are matched. After that, by opening the contact 4a, it is possible to quickly return to a normal state (a state in which a short circuit has not occurred).

  Further, according to the present invention, it is possible to quickly return to the normal state. For example, if the abnormal state detection level of the protection circuit 16 is increased, the frequency of malfunctions increases and even if a malfunction occurs, the normal state is restored. There is no hassle. That is, even if the abnormal state detection level such as quenching is increased, there is no trouble (there is no trouble in returning to the normal state), and the abnormal state detection level is increased to make the contact 4a operate relatively sensitively. And the breakage of the excitation power source (101, 201) and the superconducting magnet 2 can be prevented more than before. The same applies to abnormalities in the excitation power source, abnormalities such as a momentary voltage drop or power failure of the main power supply.

  In the first embodiment, the first shunt resistor 5 for detecting the current flowing in the superconducting coil 2L in the loop A is used, and the detected value is set as the target value. However, as a modified example, The output current value of the power unit 3 is controlled using the detected value of the first shunt resistor 5, and the output current value of the power unit 3 is controlled using the detected value of the second shunt resistor 8 when returning from the protected state. You may do it. In this way, the control in the excitation power supply 101 is configured to switch the output current control current detector between the normal time and the return time. On the other hand, the output current control at the time of returning from the protection state may be relatively rougher than the normal output current control. That is, according to this configuration, even if the second shunt resistor 8 is a current detector with rough accuracy (low accuracy) and the current flowing through the superconducting coil 2L is protected (contact 4a is closed). There is an advantage that current detection (display) with higher accuracy is possible with the first shunt resistor 5 with higher accuracy.

  In the first embodiment, the second shunt resistor 8 may be used for controlling the output current value of the power unit 3 at the normal time and at the time of return, and the first shunt resistor 5 may be merely used for display. In this case, when the operator returns from the protected state, the operator sets the display value of the first shunt resistor 5 as the set value for return and increases the output current value of the power unit 3, and when IA and IB match. It is also possible to open the contact 4a and complete the return. Further, in the above, the operator finally confirms whether IA and IB match. Thereafter, the operator presses a button for manually opening the contact 4a.

(Third embodiment)
FIG. 4 is a block diagram showing an excitation power supply 301 according to the third embodiment of the present invention. The major difference between this embodiment and the first embodiment is that the excitation power supply 301 of this embodiment includes two (plural) power units. The excitation power supply may be provided with three or more power units.

  As shown in FIG. 4, the excitation power source 301 includes a power source 1, a first power unit 13, a second power unit 23, a first shunt resistor 5 (first current detector), a main control circuit 12 (main control means), and a distributor. 14 (command value distribution means), a sweep plate setting device 33, a protection circuit 16 (protection means), a return button 32, and a return circuit 131.

(First current detector)
The first shunt resistor 5 is a current detector that detects the output current value of the entire excitation power supply 301. Further, it is provided at a position where the output current value in the loop A including the superconducting coil 2L and the contact 4a of the protection relay 4 (the total output current value of the two power units 13 and 23) can be detected in the protected state.

(Power unit)
Two power units 13 and 23 are connected to the power source 1. The first power unit 13 includes a transistor 17 (usually a plurality of transistors) that is an amplifier, a second shunt resistor 18 (second current detector) that detects an output current value of the power unit 13, and an output current value of the power unit 13. And a current control circuit 19 (current control means) for controlling.

  The second power unit 23 has the same configuration as that of the first power unit 13. The second power unit 23 includes a transistor 27 (usually a plurality of transistors) that is an amplifier and a second shunt resistor 28 that detects an output current value of the power unit 23. (Second current detector) and a current control circuit 29 (current control means) for controlling the output current value of the power unit 23 are provided.

  The main control circuit 12, the distributor 14, the switch 30, the return circuit 131, the return button 32, and the sweep plate setting device 33 are regarded as components of the power units 13 and 23 (components common to the power units 13 and 23). Also good.

(Main control means)
The main control circuit 12 is for setting and controlling the output current value of the entire excitation power supply 301, and the setting function portion of the main control circuit 12 includes a digital-analog conversion circuit (DAC). By setting the output current value to be maintained by the excitation power supply 301, the output current value analogized from the microcomputer circuit via the DAC is output as a command value to the control portion in the main control circuit 12.

  The control part of the main control circuit 12 is configured to output a current command value to the distributor 14 so that the detected value (current value) of the first shunt resistor 5 becomes equal to the set output current value of the entire excitation power supply 301. ing. Specifically, the deviation between the detected value of the first shunt resistor 5 and the set output current value is obtained, and a current command value proportional to the obtained deviation is output to the distributor 14.

(Command value distribution means)
The distributor 14 is configured to distribute the current command value output from the main control circuit 12 to each power unit (13, 23). When the current capacities of the first power unit 13 and the second power unit 23 are equal, the distributor 14 is configured to evenly distribute the current command value output from the main control circuit 12. When the current capacity ratio between the first power unit 13 and the second power unit 23 is 2: 3, the distributor 14 is configured to distribute the current command value output from the main control circuit 12 to 2: 3.

(About current control circuits 19 and 29)
Here, the current control circuits 19 and 29 provided in the respective power units 13 and 23 are configured so that the detected values (current values) of the second shunt resistors 18 and 28 are distributed from the distributor 14 and output as current command values. The output current values of the power units 13 and 23 are controlled to be equal.

  The protection relay 4 is configured to close the contact 4 a when receiving a signal from the protection circuit 16. Note that the protection circuit 16 also receives an internal abnormality signal 100 such as a momentary voltage drop or power failure generated from a controller (not shown) using a microcomputer. Further, the protection relay 4 is configured to open the contact 4a when receiving a signal from the return circuit 131 (in the state of IA = IB1 + IB2).

(switch)
The switch 30 is a switch for switching one of the signal from the main control circuit 12 and the signal from the return circuit 131 to enter the distributor 14. The switch 30 is operated by the return circuit 131.

(Excitation power supply operation)
Next, the operation of the excitation power supply 301 in the normal state (not in the protected state) will be described.

  The excitation power supply 301 according to the present embodiment includes a protection circuit operation (contact 4a is closed) or a return mode (contact 4a is closed, IA and IB are matched, and then the contact 4a is opened). In a normal state that is not a series of states), there is a function of preventing or reducing the current drift phenomenon. The drift phenomenon here refers to an action that compensates for the output current of a power unit that has failed in another normal power unit when a defect such as component failure or conductor deterioration occurs for some reason within a power unit. This is a phenomenon in which the output current is biased to other normal power units.

  As a scene where the current drift phenomenon occurs, for example, the performance of the cooling device (not shown) provided in the first power unit 13 decreases and the temperature in the first power unit 13 rises. More current may flow than other normal second power units 23. In this case, a current smaller than that of the first power unit 13 flows through the second power unit 23 so as to compensate for an excessive current flowing through the first power unit 13 (a drift phenomenon). Further, for example, a drift phenomenon may occur due to deterioration of elements such as the transistor 17 in the first power unit 13.

  According to the excitation power supply 301 according to the present embodiment, the output current value obtained by measuring the voltage generated at both ends of the first shunt resistor 5 by the main control circuit 12 is obtained in the overall current setting command unit (not shown). Control is performed so as to output current command values to the first power unit 13 and the second power unit 23 so that the set output current value is obtained, and the current command value output from the main control circuit 12 by the distributor 14 is used as the first power unit 13. And distributed to the second power unit 23. The current control circuit 19 (current control circuit 29) of the first power unit 13 (second power unit 23) is detected by measuring the voltage generated at both ends of the second shunt resistor 18 (second shunt resistor 28). The output current value is controlled to be the current command value distributed by the distributor 14. As a result, if a component failure or the like occurs in an element such as the transistor 17 in the first power unit 13 and the first power unit 13 cannot flow a predetermined current, a current that compensates for it from the main control circuit 12 Although the command value is issued, the current command value is distributed to the first power unit 13 and the second power unit 23 by the distributor 14. Since the current control circuit 19 and the current control circuit 29 of the first power unit 13 and the second power unit 23 are controlled so as to have the current command value distributed by the distributor 14, the current flows to the normal second power unit 23. Therefore, the current is leveled as a whole, and the drift phenomenon can be prevented.

  Further, the amplification factors of the current control circuit 19 and the current control circuit 29 are smaller than the amplification factor of the main control circuit 12. As a result, the current control circuit 19 and the current control circuit 29 in the first power unit 13 and the second power unit 23 are allowed to have a slight drift phenomenon, and the main control circuit 12 performs severe current control, so that Stabilization can be achieved. That is, an extreme drift phenomenon in the entire excitation power supply 301 can be prevented.

  The first shunt resistor 5 is a resistor with higher accuracy than the second shunt resistors 18 and 28. Thereby, the cost of the excitation power supply 301 can be reduced.

  The distributor 14 does not necessarily have the configuration of the present embodiment, and it is sufficient that the entire control system (the current command value of the entire excitation power supply 301 (the entire power unit)) can be divided into the current commands of the power units 13 and 23 and input. .

(Description of protection status)
When the protection circuit 16 detects quenching while the superconducting coil 2L is energized, the signal enters the main control circuit 12 via the protection circuit 16 and sets the current command to zero. As a result, IB1 and IB2 output from the power elements 17 and 27 become zero. The protection circuit 16 closes the contact 4a at the same time. The current IA that has been flowing through the superconducting coil 2L until then flows to the contact 4a. Here, when the superconducting coil 2L is really quenched, IA attenuates rapidly. On the other hand, when this quench detection is a false detection, IA hardly attenuates and it takes a long time to attenuate.

  Therefore, when the return button 32 is pressed, the return circuit 131 first switches the output of the main control circuit 12 to the output of the return circuit 131. The switch 30 is switched from the contact 30a to the contact 30b. Similarly to the main control circuit 12, the current detection value is input from the first shunt resistor 5 to the return circuit 131. The return circuit 131 uses the detected value of the first shunt resistor 5 as a target value to generate and output a command value for gradually increasing the current command from the value of the sweep plate setting device 33 to the distributor 14. The distributor 14 distributes the current command to the two power units (13, 23) in the same manner as in the normal state (the state that is not the protection state). When the command current reaches the target value IA using the sweep plate determined by the return circuit 131, the total value of the currents IB1 and IB2 of the two distributed power units (13 and 23) also matches IA.

  As described above, in the excitation power supply 301, the return circuit 131 operates in the same manner as the excitation power supply in the first and second embodiments, and the detected values of the first shunt resistor 5 and the second shunt resistors 18 and 28 (second shunt resistor 18). (A total value of 28 detected values) is used to match the output current value of the entire power unit with the current value flowing through the superconducting coil 2L, and then the contact 4a is opened, thereby suddenly changing the current after the contact 4a is opened. It also has a function to prevent it.

  The difference between the return mode and the normal mode is that in the normal mode, the first shunt resistor 5 captures the entire current and outputs it to the distributor 14 so as to correct the error with the overall command. Only the current command value created by the return circuit 131 is output to the distributor 14. As a result, IB1 and IB2 are controlled with the accuracy of the second shunt resistors 18,. Here, for example, the second shunt resistors 18 and 28 have rough accuracy (low current detection accuracy) from the viewpoint of cost reduction as compared with the entire shunt (first shunt resistor 5). In addition, because of the double control system, the feedback gain of each unit (power units 13 and 23) is relatively low. Therefore, IB1 and IB2 may be slightly rough values as compared with the normal mode. However, (IB1 + IB2) .apprxeq.IA is sufficient, and if there is almost a match, then the normal mode is resumed, and some errors do not become a problem.

  When IB1 + IB2 substantially coincides with IA, the return circuit 131 transfers the current value IA to the main control circuit 12. Then, the switch 30 is switched to the 30a side and the contact 4a is opened at the same time. Thereafter, the current is controlled in the normal mode while being held at the set current value IA. Note that IA may use a value stored in the main control circuit 12 when a quench occurs. If the detected current value IA is used, there is a slight error from the current value of the superconducting coil 2L to be originally controlled when returning to the normal mode. In this case, fine adjustment is performed by a normal method.

  In the third embodiment, the main control circuit 12 and the return circuit 131 are described as separate circuits. However, in terms of function, the current detection value of the first shunt resistor 5 is used as a feedback signal (main Control circuit), the current detection value of the first shunt resistor 5 is used as a target value (recovery circuit), and the output value of the distributor 14 is slightly different, but the circuit configuration of the first shunt resistor 5 It is common to receive a signal input, receive a signal from the sweep plate setting unit 33, and create a current signal of a predetermined sweep plate. Generally, these measures are analog-converted and output by a microcomputer and a DA converter. Therefore, (1) the input of the return button 32 cannot be seen, (2) the difference in handling of the detection value of the first shunt resistor 5, (3) the difference in the content of the signal output to the distributor 14, Is a small difference in the program of the microcomputer which is built, it is preferable to integrate the main control circuit 12 and the return circuit 131.

(Fourth embodiment)
FIG. 5 is a block diagram showing an excitation power source 401 according to the fourth embodiment of the present invention. An excitation power supply 401 according to this embodiment is a modification of the excitation power supply 301 according to the third embodiment. As shown in FIG. 5, the excitation power source 401 includes a power source 1, a first power unit 13, a second power unit 23, a first shunt resistor 5 (first current detector), a main control circuit 12 (main control means), and a distributor. 14 (command value distribution means), a sweep plate setting device 33, a protection circuit 16 (protection means), a return button 32, and a return circuit 231.

  For example, the return control after the contact 4a is closed by the protection circuit 16 will be described below. After the current value of IA is detected by the first shunt resistor 5, (IB 1 + IB 2) is controlled using this as a target value, but in the return operation, the total value of the current detection values of the second shunt resistor 18 and the second shunt resistor 28 is controlled. (IB1 + IB2) is obtained by the adder 304 for generating. Instead of the signal from the first shunt resistor 5 in the normal mode, the main control circuit 12 receives a switching signal from the adder 304 through the switches 302 and 303. The switches 302 and 303 are activated (switched) by a signal from the return circuit 231.

  When IA and (IB1 + IB2) coincide with each other, the contact 4a and the switches 302 and 303 are switched by the return circuit 231 to return to the normal state (the contact 4a is opened. The switches 302 and 303 are set to the 302a and 303a side. ). The 302a and 303a sides of the switches 302 and 303 are the normal mode, and the 302b and 303b sides are the return mode. Further, the detected value of the first shunt resistor 5 may be always (always) input to the main control circuit 12 to cope with IA that gradually attenuates.

  In the return mode (return control), since the total value of the current detection values of the second shunt resistors 18 and 28 for preventing current drift is used instead of the first shunt resistor 5, the second shunt resistors 18 and 28 are related to cost design. May have a relatively rough accuracy. In this case, the current detection accuracy decreases only at the time of return (in the return mode). However, after returning to normal mode, the control shifts to control using the first shunt resistor 5 (overall shunt), and the subsequent current control accuracy returns to normal. The role of this return mode is to apply a large current change to the superconducting coil 2L at the time of return so as not to cause a quench or the like, and this level of error (error in current measurement accuracy) does not cause a problem (a large current change does not occur). ).

(Fifth embodiment)
FIG. 6 is a block diagram showing an excitation power source 501 according to the fifth embodiment of the present invention. In the excitation power source 501 of this embodiment, the first shunt resistor 5 used in the excitation power source 101 of the first embodiment is omitted, and the memory circuit 50 is incorporated in the power unit 43 instead. The storage circuit 50 is a storage unit that stores the output current value of the power unit 43 at or immediately before the contact point 4a is closed by the return circuit 31. In the example shown in FIG. 6, the storage circuit 50 stores the detection value of the shunt resistor 8 (current detector), but the storage circuit 50 stores the current command value for the current control circuit 9. It may be configured to. There are various storage means such as a battery-backed RAM and a non-volatile memory. Usually, in order to digitize, it is stored in the storage means via an ADC (analog-digital converter) or the like.

  The return circuit 31 of the present embodiment uses the detected value of the shunt resistor 8 and the stored value of the storage circuit 50 when the contact 4a is closed by the protection circuit 16 to determine the output current value of the power unit 43 and the superconducting coil 2L. It is a return means for opening the contact point 4a and returning from the protected state after matching the value of the flowing current. This will be specifically described below.

  For example, when an abnormality of the superconducting magnet 2 is detected, the protection circuit 16 sends a signal to the storage circuit 50, the current command circuit 10, and the protection relay 4 almost simultaneously. Thereby, the memory circuit 50 stores the output current value of the power unit 43 at this time. The current command circuit 10 sets the current command value to the current control circuit 9 to zero, and the output of the power unit 43 is set to zero. Further, the contact 4a is closed by the operation of the protection relay 4, and the output of the power unit 43 is short-circuited. The protection circuit 16 is connected to the storage circuit 50 at a timing at which the storage circuit 50 can store the output current value (normal time) before the contact 4a is closed and before the output of the power unit 43 drops to zero. Send a signal.

  Of course, when the control including the abnormality treatment is performed by the microcomputer or the sequencer, the signal of the instantaneous power failure detection circuit incorporated therein cannot be input to the protection circuit 16 (the power failure is detected by the sequencer). If it is detected, the status is output to the outside and the sequencer itself stops, so it cannot be used thereafter.) A separate instantaneous stop detection circuit is provided and this signal is input to the protection circuit 16 or, for example, a microcomputer that is not used for anomaly treatment Alternatively, if there is a sequencer, the signal of the instantaneous power failure detection circuit incorporated in the sequencer is input to the protection circuit 16. In addition, the microcomputer, sequencer, or other device that performs control, including abnormal measures, has its power supply part so that it can function for a while (for example, about 3 seconds) even after the instantaneous power failure detection circuit detects the instantaneous power failure. It is necessary to have a larger electrolytic capacitor than usual, or a means for switching to battery driving.

  Here, when the abnormality of the superconducting magnet 2 is a false detection, the current IA is attenuated by L and R, but the attenuation is slight because L is very large and R is very small. Is about 1%. On the other hand, if the operator notices an abnormal condition, the operator presses the return button 32. As a result, the storage circuit 50 reads the stored value of, for example, 200A, and the output circuit IB of the power unit 43 is controlled to 200A. When a command for controlling IB to 200A is issued, the return circuit 31 determines that IB and IA match, and the return circuit 31 opens the contact 4a. Actually, even if IA is attenuated to 198A, if the difference is about this level, the superconducting magnet 2 will not be quenched and the excitation power source 501 will not break down, and the current flowing through the magnet will be adjusted to 200A immediately. Is done.

According to the excitation power source 501, only one current detector is required. If it is assumed that a microcomputer is originally used for the control, calculation and storage can be handled by a microcomputer program (software), so there is an advantage that a current detector as a hardware component can be omitted.
(Sixth embodiment)
FIG. 7 is a block diagram showing an excitation power source 601 according to the sixth embodiment of the present invention. The excitation power source 601 of this embodiment is a modification of the excitation power source 501 according to the fifth embodiment. In the present embodiment, the timer 51 and the correction circuit 52 are further incorporated in the power unit 53.

  The timer 51 is a timer that measures an elapsed time from the time when the storage circuit 50 stores the output current value of the power unit 53. The correction circuit 52 is a current value correction means for correcting the stored value of the storage circuit 50 from the elapsed time measured by the timer 51 and the correction value per time stored in advance.

  Note that the return circuit 31 of the present embodiment outputs the output of the power unit 53 using the detected value of the shunt resistor 8 and the stored value of the storage circuit 50 corrected by the correction circuit 52 when the contact 4a is closed by the protection circuit 16. The contact point 4a is opened after matching the current value with the current value flowing through the superconducting coil 2L. This will be specifically described below.

  For example, it is assumed that the protection relay 4 is operated due to an erroneous detection of the superconducting magnet 2 and the contact 4a is closed. After 5 minutes, the operator notices an abnormal state and presses the return button. At this time, the correction circuit 52 reads, for example, a stored value of 200 A in the storage circuit 50 and reads a value of, for example, 5 minutes (measured elapsed time) of the timer 51. Then, the correction circuit 52 estimates (calculates) IA that should be somewhat attenuated from the 200 A and the value of 5 minutes. The attenuation curve is linear for a short time, and if the attenuation value of 0.4 A per minute and the correction value are stored in advance in the correction circuit 52, the calculation that the 2 A attenuation should have occurred in 5 minutes is calculated. Easily. Assuming that the difference between the time when the contact 4a is closed and the time when the operator presses the return button is a long time, it is possible to make the correction circuit 52 perform more complicated calculation. For example, it is possible to cause the correction circuit 52 to perform more complicated calculations such as storing L and R and obtaining the current attenuation based on the values of L and R and the measured elapsed time. Assuming that a microcomputer is originally used for control, the correction circuit 52 is preferably integrated with other circuits such as the memory circuit 50 and configured by a microcomputer.

  Thereafter, the correction value 198A (200−0.4 × 5) is read by the return circuit 31, and the output IB of the power unit 53 is controlled to 198A. When a command for controlling IB to 198A is issued, the return circuit 31 determines that IB and IA match, and the return circuit 31 opens the contact 4a.

  According to the excitation power source 601, by further including the timer 51 and the correction circuit 52, it is possible to return from the protected state more reliably than the excitation power source 501. It should be noted that both the excitation power source 501 and the excitation power source 601 are preferably provided with a time limit that allows recovery. For example, the excitation power source 501 can be restored within 10 minutes, and the excitation power source 601 can be restored within, for example, 3 hours, depending on a calculation error. The method shown in the excitation power sources 501 and 601 such as replacing the first shunt resistor 5 with the storage circuit 50 can be applied not only to the excitation power source 101 but also to the excitation power sources 201, 301, and 401.

(Process after instantaneous voltage drop detection)
In all the embodiments described above, the processing after the instantaneous voltage drop is detected is as follows. For example, when a microcomputer (not shown) detects an instantaneous drop, the circuit is configured such that the current command is set to zero and the contact 4a is closed. When the contact 4a is closed, the superconducting magnet 2 is circulated through this contact, and the current continues to flow through the superconducting coil 2L. The resistance in the superconducting magnet 2 is zero, and there are other resistances such as lead wires connecting the excitation power supply and the superconducting magnet 2, contact resistance of the contact, shunt 5, etc. The ratio of consuming energy stored in the superconducting magnet 2 is The current that flows is small and does not decrease in a short time. For example, even if there is an abnormal normal state for 5 minutes, it attenuates only about 1%.

  If the operator presses the recovery button after confirming that it is in an abnormal state due to a momentary drop, for example, if the current used at 200A is attenuated to IA = 198A in a short-circuit state, IB After the adjustment at 198A, the contact 4a is opened to switch to the current supply from the power unit, and then it can be restored to 200A again. As a result, the work using the magnetic field can be restored without any actual harm. Further, a power failure confirmation signal function for confirming power failure may be added, and this power recovery confirmation signal may be used instead of pressing the return button 32. On the other hand, even if UPS is installed for power failure and only the control system is backed up, the power system is often large and cannot be backed up. In this case, the power unit cannot be moved even if the control is alive, so the contact 4a is short-circuited. It is effective.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

1: Power supply 2: Superconducting magnet 2L: Superconducting coil 3: Power unit 4: Protection relay 4a: Contact 5: First shunt resistor (first current detector)
7: Transistor (amplifier)
8: Second shunt resistor (second current detector)
9: Current control circuit (current control means)
16: Protection circuit (protection means)
100: Internal abnormality signal 101: Excitation power supply

Claims (2)

An exciting power source for exciting a superconducting magnet having a superconducting coil,
Power supply,
A power unit connected to the power source;
If the erroneously detected quenching before Symbol superconducting magnet, and a protective means to protect state closes the contacts to short-circuit across the output of the power unit,
A first current detector provided in a loop including the superconducting coil and the contact, and detecting a current value in the loop;
With
The power unit is
An amplifier;
A second current detector for detecting an output current value of the power unit;
Current control means for controlling the output current value;
Have
When the contact is closed by the protection means, at least the detection value of the first current detector is used to increase the output current value with a predetermined sweep rate and flow through the output current value and the superconducting coil. It is equipped with a return means that opens the contact after matching the current value and returns from the protected state ,
When the return button is pressed, the return means reads the detection value of the first current detector as a target value, sets the detection value of the second current detector as a current value, and sets both detection values with a predetermined sweep rate. An excitation power source for a superconducting magnet, characterized in that the contacts are opened after matching . An exciting power source for exciting a superconducting magnet having a superconducting coil,
Power supply,
A power unit connected to the power source;
If the erroneously detected quenching before Symbol superconducting magnet, and a protective means to protect state closes the contacts to short-circuit across the output of the power unit,
When the contact is closed by the protection means, storage means for storing the output current value of the power unit at that time or immediately before,
With
The power unit is
An amplifier;
A current detector for detecting the output current value of the power unit;
Current control means for controlling the output current value;
Have
When the contact is closed by the protection means, the output current value is increased by a predetermined sweep rate using the detection value of the current detector and the storage value of the storage means, and the output current value and An excitation power source for a superconducting magnet, comprising: a return means for opening the contact after returning the value of the current flowing through the superconducting coil to coincide with the protection state.