JP2012235574A - Excitation power source for superconductive magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excitation power source for a superconductive magnet which eliminates a dead time from when abnormality is detected till when the output is short-circuited by the operation of a mechanical switch, and can short-circuit the output more surely than before.SOLUTION: An excitation power source 102 that excites a superconductive magnet 2 provided with a superconductive coil 3 includes: an instantaneous interruption detection circuit 30 for outputting an abnormal signal when detecting instantaneous interruption abnormality of the excitation power source; a clamper 6 which is arranged in parallel to the superconductive coil 3, and short-circuits both ends of the output to the superconductive coil 3 by inputting the abnormal signal sent from the instantaneous interruption detection circuit 30; and a semiconductor switch element 20 which is arranged in parallel to the superconductive coil 3 and the clamper 6, and short-circuits both ends of the output to the superconductive coil 3 by inputting the abnormal signal sent from the instantaneous interruption detection circuit 30.

Description

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

  Protection circuits for excitation power for superconducting magnets are roughly classified into those that cut off the output to the superconducting coil and those that short-circuit the output to the superconducting coil. If any abnormality of the excitation power source or the superconducting magnet is detected, it is a safe protection method to disconnect (cut off) the mutual connection. 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

  Nevertheless, a protection method that interrupts a contact point that is energized is not suitable for large current control. As a protection method in the control of a large current, a method is generally employed in which both ends of the output from the excitation power supply to the superconducting coil 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 to the superconducting coil has the following points to be improved. When a false detection such as a quench occurs (a signal indicating that the superconducting coil is not quenched yet is output), or when a power failure occurs on the primary power supply, both ends of the excitation power supply It is important how quickly the short circuit occurs. If the timing of the short circuit is late, the superconducting coil may be quenched due to a sudden change in current. That is, it is desirable to short-circuit both ends of the output to the superconducting coil (both ends of the output of the excitation power source) as soon as possible when an erroneous detection such as quenching or a power failure of the primary power source occurs.

  Conventionally, a mechanical switch is used as means for short-circuiting the output. A general mechanical switch operates after a lapse of time after an abnormal signal is input. Although there is a mechanical switch having a high operating speed, this mechanical switch having a high operating speed has a chattering problem and has an instability. Further, when an abnormality is detected in the superconducting magnet or the excitation power source, the output to the superconducting coil is to be short-circuited reliably, but conventionally, this has been a single measure of short-circuiting with a mechanical switch.

  The present invention has been made in view of the above circumstances, and its purpose is to eliminate the dead time from detection of abnormality until the output is short-circuited by the operation of the mechanical switch, and to short-circuit the output more reliably than before. It is an object to provide an exciting power supply for a superconducting magnet having a circuit configuration that can be applied.

  In order to achieve the above object, the present invention provides an excitation power source for exciting a superconducting magnet having a superconducting coil, and outputs an abnormality signal when an abnormality of the superconducting magnet or the excitation power source is detected. A circuit, a mechanical switch that is arranged in parallel with the superconducting coil, and short-circuits both ends of the output to the superconducting coil when an abnormal signal is input from the abnormality detecting circuit, and the superconducting coil and the mechanical switch An exciting power supply for a superconducting magnet is provided, which is arranged in parallel and includes an electrical switch that short-circuits both ends of the output to the superconducting coil when an abnormality signal is input from the abnormality detection circuit.

  Since the electrical switch operates instantaneously, by using the electrical switch together with the mechanical switch as a means to short-circuit both ends of the output to the superconducting coil, until the output is short-circuited due to the operation of the mechanical switch Dead time can be eliminated. In addition, using an electrical switch together with a mechanical switch improves the robustness of the system by providing a double protection measure. That is, the output can be short-circuited more reliably than in the past.

  In the present invention, the abnormality detection circuit is provided in a control circuit that controls output to the superconducting coil, and outputs a first abnormality detection circuit that outputs an abnormality signal to the mechanical switch; and the first abnormality detection circuit; And a second abnormality detection circuit that is provided separately and outputs an abnormality signal to the electric switch. According to this configuration, it becomes a two-line abnormality detection circuit, and the robustness is further improved.

  Furthermore, in the present invention, the second abnormality detection circuit may be configured to output an abnormality signal to the electric switch via the control circuit.

  According to this configuration, the signal system to the mechanical switch and the signal system to the electrical switch can be partially shared, and a simple circuit configuration is obtained.

  In the present invention, the second abnormality detection circuit may be further configured to output an abnormality signal directly to the electric switch.

  According to this configuration, since the signal system to the electric switch is doubled, the robustness of the system is further improved.

  According to the present invention, an electric switch for short-circuiting both ends of the output to the superconducting coil is arranged in parallel with the mechanical switch, thereby eliminating the dead time from the detection of the abnormality until the output is short-circuited by the operation of the mechanical switch. At the same time, the output can be short-circuited more reliably than before.

It is a block diagram which shows the excitation power supply which concerns on 1st Embodiment of this invention. It is a detailed block diagram of the clamper shown in FIG. It is a detailed block diagram of the semiconductor switch shown in FIG. It is a block diagram which shows the excitation power supply which concerns on 2nd Embodiment of this invention. It is a detailed block diagram of the instantaneous power failure detection circuit shown in FIG. It is a block diagram which shows the excitation power supply which concerns on 3rd Embodiment of this invention. It is a detailed block diagram of the instantaneous power failure detection circuit shown in FIG. It is a detailed block diagram of the semiconductor switch shown in FIG. It is a block diagram which shows the excitation power supply which concerns on 4th Embodiment of this invention. It is a figure which shows the modification of the instantaneous power failure detection circuit shown in FIG. It is a figure which shows the modification of the semiconductor switch shown in FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, the excitation power source 1 according to the first embodiment of the present invention will be described with reference to FIGS.

(First embodiment)
(Excitation power source configuration)
As shown in FIG. 1, the excitation power source 1 is a power source for exciting a superconducting magnet 2 including a superconducting coil 3 and protective diodes 4 and 5. The superconducting coil 3 is formed by winding a superconducting wire. The protective diodes 4 and 5 are arranged in parallel with the superconducting coil 3.

  The excitation power source 1 includes a DC power source 11, a transistor 10, a control circuit 13, a clamper 6 (mechanical switch), and a semiconductor switch element 20 (electric switch).

(DC power supply)
The DC power supply 11 is a transformer (not shown) connected to a primary power supply (AC power supply), or a transistor circuit (not shown) that supplies a DC current that is rectified and smoothed from the AC power of the transformer to the superconducting coil 3. Etc. In the DC power supply 11, a commercially available switching regulator or the like may be used.

(Transistor)
The transistor 10 is a general bipolar transistor. A power element such as a field effect transistor (FET), IGBT, or MOSFET may be used.

(Control circuit)
The control circuit 13 is a circuit that controls output to the superconducting coil 3 (output of the DC power supply 11). The control circuit 13 can control the output voltage of the DC power supply 11 and control the output voltage to minus. Instead of the constant voltage control circuit 13, a constant current control circuit may be used. The constant current control circuit is a circuit that controls the current detected by a current detector (not shown) so that the current (output current) flowing through the superconducting coil 3 has a constant current value.

  There are various methods for controlling the excitation power source. Besides the transistor dropper method shown in FIG. 1, there are a bridge type and a bridge type PWM control.

(Mechanical switch)
A clamper 6, which is a mechanical switch, is connected in parallel to the superconducting coil 3. The clamper 6 is a switch for short-circuiting both ends of the output to the superconducting coil 3 by an abnormal signal input via the electric signal path 14. The above-described control circuit 13 incorporates an abnormality detection circuit that outputs an abnormal signal to the electric signal path 14 when an abnormality of the superconducting magnet 2 (superconducting coil 3) or the excitation power source 1 is detected. Since this abnormality detection circuit has a known circuit configuration and can be easily realized, detailed description thereof will be omitted.

  As shown in FIG. 2, the clamper 6 is a relay including a contact 6a, a coil 6b, and a transistor 6c, and includes a B contact. The B contact is a contact that operates with an electrical signal Low configured such that the contact 6a is closed by the electrical signal Low and the contact 6a is opened by the electrical signal High. Normally, the electric signal High is input from the electric signal path 14, and the transistor 6c is turned on, whereby the coil 6b is excited and the contact 6a is opened by electromagnetic force. On the other hand, when an abnormal signal (electric signal Low) is input from the electric signal path 14, the transistor 6c is turned off, the coil 6b is de-energized, and the contact 6a is closed by the spring force. Thereby, both ends of the output to the superconducting coil 3 are short-circuited.

  The clamper 6 may be configured with a B contact as in the present embodiment, or may be configured with an A contact. The A contact is a contact that operates with an electric signal High configured such that the contact 6a is opened by the electric signal Low and the contact 6a is closed by the electric signal High. The selection of whether the clamper 6 is configured with an A contact or a B contact varies depending on which one is considered to be a safe side or the circumstances of the circuit configuration. This embodiment is an example in which it is considered safe that the coil 6b is in a non-excited state and the contact 6a is closed when there is a disconnection of the wiring.

(Electric switch)
A semiconductor switch element 20, which is an electrical switch, is connected in parallel to the superconducting coil 3 and the clamper 6. The semiconductor switch element 20 is a switch that short-circuits both ends of the output to the superconducting coil 3 by an abnormal signal input through an electric signal path 27 branched from the electric signal path 14.

  As shown in FIG. 3, the semiconductor switch element 20 is a relay including a photocoupler 24, N-channel power MOSFETs 21 and 22, and a capacitor 25. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. A semiconductor having an NPN structure is called an N channel. The capacitor 25 is an electric field capacitor.

  As for the N-channel power MOSFET 21, the drain D is used on the positive side with respect to the source S (normal usage). On the other hand, with respect to the N-channel power MOSFET 22, the drain D is used on the negative side with respect to the source S, which is contrary to the normal case. This usage method utilizes the fact that the N-channel power MOSFET can pass a current even if the drain D and the source S are reversed. In the N-channel power MOSFET, when the gate G is + 10V with respect to the source S, the resistance between the drain D and the source S is almost zero, and when the gate G is 0V with respect to the source S, the drain D and the source S There is a property that the resistance between is almost infinite.

  When an abnormal signal is input to the photocoupler 24 from the electric signal path 27, the transistor inside thereof is turned on to generate a voltage (for example, 10V) in the resistor 23, the N-channel power MOSFETs 21 and 22 are turned on, and both FETs are turned on. The resistance between the drain D and the source S becomes almost zero. Thereby, both ends of the output to the superconducting coil 3 are short-circuited.

  When the semiconductor switch element 20 is not provided with the N-channel power MOSFET 22 but only the N-channel power MOSFET 21, a negative direction (a direction from bottom to top in FIG. 3) due to a structurally incorporated body diode (parasitic diode). Is always on. In the present embodiment, two N-channel power MOSFETs 21 and 22 are arranged in series so as to function similarly in both directions. The capacitor 25 has a sufficiently large capacity so that a voltage remains for a while after a power failure. When the current flowing through superconducting coil 3 is large, a plurality of N-channel power MOSFETs 21 and 22 are arranged in parallel to ensure current capacity. The semiconductor switch element 20 is used in combination with a mechanical switch, and by limiting the operation time, it is not necessary to consider the heat dissipation and can be formed with a small substrate.

  Further, the polarity of control may be changed as a P-channel power MOSFET instead of the semiconductor switch element 20 using the photocoupler 24, the N-channel power MOSFETs 21 and 22, and as an electric switch using other elements. Also good.

(Movement of each switch when abnormality is detected)
The abnormality detection of the superconducting magnet 2 is a case where a quench occurs in the superconducting coil 3 and is detected. Although detection of quenching causes false detection when the detection sensitivity is increased, it is not possible to distinguish whether or not it is false detection at the time of quench detection. The abnormality detection of the excitation power source 1 includes both cases where an abnormality is detected in the DC power source 11, the control circuit 13, etc., and a power failure (especially a momentary power failure or a momentary drop) in the primary power source is detected. The primary power source refers to a power source that supplies (powers) the DC power source 11 that constitutes the excitation power source 1.

  Here, taking a case where a quench is detected as an example, the movement of each switch when an abnormality is detected will be described. When abnormality of superconducting magnet 2 (actually false detection of quenching) is detected, output current to superconducting coil 3 is made zero by control circuit 13 and an abnormal signal is output to clamper 6 and semiconductor switch element 20. Is done. When an abnormal signal (electrical signal Low) is input to the clamper 6, the transistor 6c is turned off, the coil 6b is de-energized, and the contact 6a is closed by the spring force. Thereby, both ends of the output to the superconducting coil 3 are short-circuited. On the other hand, when an abnormal signal is input to the semiconductor switch element 20, a voltage is generated in the resistor 23, the N-channel power MOSFETs 21 and 22 are turned on, and the resistance between the drain D and the source S of both FETs becomes almost zero. Become. Thereby, both ends of the output to the superconducting coil 3 are short-circuited.

  Here, since the contact 6a of the clamper 6 is closed by a spring force, it takes a short time until the contact 6a is closed after an abnormal signal is input to the clamper 6. On the other hand, the semiconductor switch element 20 operates instantaneously. By using the semiconductor switch element 20 together with the mechanical clamper 6 as a means for short-circuiting both ends of the output to the superconducting coil 3, dead from the detection of abnormality until the output is short-circuited by the operation of the clamper 6 (contact 6a is closed). Time can be lost. Further, the use of the semiconductor switch element 20 together with the mechanical clamper 6 improves the robustness of the system by providing a double protection measure. That is, the output can be short-circuited more reliably than in the conventional case where only the mechanical clamper 6 is used.

  Note that after the output to the superconducting coil 3 is short-circuited, if the quench has actually occurred, the process waits until the quench state is settled. On the other hand, if it is clear that the quench has been erroneously detected, the control circuit 13 controls the output current of the DC power supply 11 so that the output current of the DC power supply 11 matches the current flowing through the superconducting coil 3, and then the clamper. 6 is opened (the clamper 6 is opened), and the resistance between the drain D and the source S of the N-channel power MOSFETs 21 and 22 is returned to almost infinite (the semiconductor switch element 20 is opened).

(Second Embodiment)
The excitation power supply 102 according to the second embodiment of the present invention will be described with reference to FIGS. The difference from the first embodiment is that, in the second embodiment, an external instantaneous power failure detection circuit 30 is added to the excitation power source. The abnormality detection circuit that is incorporated in the control circuit 13 and outputs an abnormality signal to the clamper 6 corresponds to the first abnormality detection circuit in the present invention, and the instantaneous power failure detection circuit 30 corresponds to the second abnormality detection circuit in the present invention. As shown in FIG. 4, the excitation power source 102 is configured so that the instantaneous power failure detection circuit 30 outputs an abnormal signal to the semiconductor switch element 20 via the control circuit 13. An abnormal signal is output from the instantaneous power failure detection circuit 30 to the control circuit 13 via the electric signal path 35.

(Instantaneous power failure detection circuit)
As shown in FIG. 5, the instantaneous power failure detection circuit 30 is an electric circuit including a transformer 31 (transformer), a photocoupler 33, and a timer IC 34. When AC200V is stepped down by the transformer 31 and inserted into the photocoupler 33, a half-wave rectified waveform pulse signal is generated by the photocoupler 33. This waveform pulse signal is input to the reset terminal of the timer IC 34. Assume that the time setting of the timer IC 34 is, for example, 20 msec. When a power failure occurs and the waveform pulse signal does not enter the timer IC 34 and 20 msec elapses, an abnormal signal is output from the instantaneous power failure detection circuit 30 to the electrical signal path 35.

  If an AC input type photocoupler is used, a full-wave rectified waveform pulse signal is obtained, and more accurate abnormality (power failure) detection can be performed. A circuit in which the transformer 31 is replaced with a resistor or a capacitor may be used.

  According to the excitation power source 102 of the present embodiment, providing two abnormality detection circuits in the excitation power source results in two types of abnormality detection circuits, and the robustness is further improved. Further, since the instantaneous power failure detection circuit 30 is configured to output an abnormal signal to the semiconductor switch element 20 via the control circuit 13, a signal system to the clamper 6 and a signal system to the semiconductor switch element 20 are provided. A part can be made common and a simple circuit configuration can be obtained.

  The external second abnormality detection circuit is not the instantaneous power failure detection circuit 30 that detects a power failure, but an overvoltage detection circuit that turns on the meter switch when the voltage of the superconducting coil 3 increases. There may be a quench detection circuit that detects the quench of the superconducting coil 3.

(Third embodiment)
The excitation power supply 103 according to the third embodiment of the present invention will be described with reference to FIGS. The difference from the second embodiment is that in the third embodiment, an abnormal signal is output from the instantaneous power failure detection circuit 30A to the control circuit 13, and an abnormal signal is directly output from the instantaneous power failure detection circuit 30A to the semiconductor switch element 20A. It is that. An abnormal signal is output from the instantaneous power failure detection circuit 30A to the control circuit 13 via the electric signal path 35a, and an abnormal signal is output from the instantaneous power failure detection circuit 30A to the semiconductor switch element 20A via the electric signal path 35b. The

(Instantaneous power failure detection circuit)
As shown in FIG. 7, the instantaneous power failure detection circuit 30A is a circuit that can output two systems of abnormal signals, and includes a transformer 31 (transformer), photocouplers 33, 37, and 38, and a timer IC 34. An electric circuit provided. Whether the signal is High when abnormal or High when normal is determined by the logic of the output of the timer IC 34, and there are many timer ICs that can be selected at any time. An abnormal signal may be directly output from the instantaneous power failure detection circuit 30A to the clamper 6.

(Electric switch)
The semiconductor switch element 20A is a switch that operates in accordance with an abnormal signal from the electrical signal paths 35a, 14, 27, or an abnormal signal from the electrical signal path 35b. FIG. 8 shows a circuit example thereof. When the photocoupler 24 or the photocoupler 28 is OFF, the gate G of the N-channel power MOSFETs 21 and 22 becomes, for example, + 10V with respect to the source S, and the N-channel power MOSFETs 21 and 22 are turned ON to be in a conductive state (short-circuit state). become. If both the photocouplers 24 and 28 are ON, a voltage is generated across the resistor 29, and the gate G of the N-channel power MOSFETs 21 and 22 becomes, for example, + 1V (almost zero) with respect to the source S. The MOSFETs 21 and 22 are turned off and become a non-conduction state (blocking state). The circuit configuration shown in FIG. 8 is an example in which the signal input to the semiconductor switch element 20A is High when normal and Low when abnormal. Of course, the circuit configuration may be Low when normal and High when abnormal.

  According to the excitation power supply 103 of the present embodiment, the operation is performed by adding a circuit for outputting an abnormal signal to the semiconductor switch element 20A without passing through the control circuit 13, that is, outputting an abnormal signal directly to the semiconductor switch element 20A. Will be faster. Further, since the signal system to the semiconductor switch element 20A is doubled, robustness can be obtained in that it operates even if one of the signal systems fails.

(Fourth embodiment)
FIG. 9 is a block diagram showing an excitation power source 104 according to the fourth embodiment of the present invention. As shown in FIG. 9, an abnormal signal may be input to the semiconductor switch element 20 only from the instantaneous power failure detection circuit 30A. In this case as well, it is preferable to input an abnormal signal from the instantaneous power failure detection circuit 30A to the control circuit 13. This is because a power failure signal (especially a momentary power failure or a momentary voltage drop) of the primary power supply can be quickly input from the momentary power failure detection circuit 30A to the clamper 6.

(Modified example of instantaneous power failure detection circuit)
The instantaneous power failure detection circuit 30 shown in FIG. 5 is a circuit that automatically cancels the abnormal signal when the power failure state is cancelled. However, even if the power failure state is canceled, the abnormal signal is retained and the abnormal signal is selfish. In some cases, it is effective to use a circuit that is not released. The instantaneous power failure detection circuit 30B illustrated in FIG. 10 is a circuit having a configuration in which an abnormal signal is retained and the abnormal signal is not canceled arbitrarily even when the power failure state is canceled.

  According to the instantaneous power failure detection circuit 30B, the abnormal signal output from the contact 37c is self-held by the coil 37a and the contact 37b even when the power failure state is canceled and the abnormal signal disappears (returns to the normal signal). It is held until it is released by the external contact 41. For the contact point 37c, it is determined by the control logic whether it is to be the A contact point or the B contact point.

(Modified example of semiconductor switch)
FIG. 11 is a diagram showing a modification of the semiconductor switch element 20 shown in FIG. Regarding the control for opening the clamper 6 and the semiconductor switch element 20 after the quench is erroneously detected and the output is short-circuited or after the output is short-circuited due to a power failure (especially a momentary power failure or a momentary drop), the clamper 6 and the semiconductor switch element 20 are controlled. As to which of the circuits is opened, there is an effect depending on whether the circuit is opened from the clamper 6 or the semiconductor switch element 20.

  The semiconductor switch element 20B shown in FIG. 11 is configured to control the opening timing of the semiconductor switch element 20B. The timing at which the semiconductor switch element 20B opens can be controlled by adding a photocoupler 28 to which a control input signal for controlling conduction of the N-channel power MOSFETs 21 and 22 is input. If the control is performed to open the semiconductor switch element 20B after opening the clamper 6, chattering of the clamper 6 can be avoided.

  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, 102, 103, 104: Excitation power supply 2: Superconducting magnet 3: Superconducting coil 6: Clamper (mechanical switch)
10: Transistor 11: DC power supply 13: Control circuit 20: Semiconductor switch element (electric switch)
30: Instantaneous power failure detection circuit (abnormality detection circuit)

Claims (4)

An exciting power source for exciting a superconducting magnet having a superconducting coil,
An abnormality detection circuit that outputs an abnormality signal when an abnormality of the superconducting magnet or the excitation power source is detected;
A mechanical switch that is arranged in parallel to the superconducting coil and shorts both ends of the output to the superconducting coil by inputting an abnormal signal from the abnormality detection circuit;
An electrical switch that is arranged in parallel with the superconducting coil and the mechanical switch, and shorts both ends of the output to the superconducting coil by inputting an abnormal signal from the abnormality detection circuit;
An excitation power source for a superconducting magnet, comprising: In the exciting power supply for the superconducting magnet according to claim 1,
The abnormality detection circuit is
A first abnormality detection circuit provided in a control circuit for controlling an output to the superconducting coil and outputting an abnormality signal to the mechanical switch;
A second abnormality detection circuit that is provided separately from the first abnormality detection circuit and outputs an abnormality signal to the electric switch;
An excitation power source for a superconducting magnet, comprising: In the exciting power supply for the superconducting magnet according to claim 2,
An excitation power supply for a superconducting magnet, wherein the second abnormality detection circuit outputs an abnormality signal to the electric switch via the control circuit. In the exciting power supply for the superconducting magnet according to claim 3,
The excitation power supply for a superconducting magnet, wherein the second abnormality detection circuit further outputs an abnormality signal directly to the electric switch.

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