JP2009206276A - Power supply circuit for superconducting coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply circuit for a superconducting coil that achieves a bipolar power supply for a superconducting coil with a simple configuration. <P>SOLUTION: The power supply circuit 1 for a superconducting coil is a circuit for supplying a bipolar DC power supply voltage Vb to a superconducting coil 2. The power supply circuit is provided with a DC power supply part 3 for outputting a monopolar DC power supply voltage Va, and a plurality of diodes 4 forward-connected between the DC power supply part 3 and the superconducting coil 2 and converting the monopolar DC power supply voltage Va into the bipolar DC power supply voltage Vb by a voltage drop action so as to supply the bipolar DC power supply voltage to the superconducting coil 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply circuit for a superconducting coil.

  A superconducting (superconducting) coil is characterized by an extremely small resistance and a large inductance compared to a normal coil. For example, the inductance of a normal coil used in a lifting magnet or a cyclotron is several henry and several tens of millihenry, respectively, while the inductance of a superconducting coil having equivalent performance is several hundred henry. Therefore, it is necessary to consider such a high inductance when supplying a current to the superconducting coil.

  That is, if the inductance of the superconducting coil is 10 Henry and the current change rate required when stopping the current supply is -1 ampere per second, in order to stop the current supply with this current change rate, the superconducting coil It is preferable to apply −10 [V] to both ends. However, at this time, the coil current flows in the positive direction until it finally becomes zero. Thus, when driving the superconducting coil, since most of the load is inductance, the coil current cannot be reduced unless a negative voltage is applied even if the direction of the coil current is positive. In order to increase the coil current at the same rate, 10 [V] may be applied to both ends of the superconducting coil. In addition, when the coil current amount is desired to be constant, the voltage across the superconducting coil is preferably set to 0 [V].

  Currently, to achieve such power control for a superconducting coil, a bipolar power supply having a regulator circuit for providing a positive voltage to the superconducting coil and another regulator circuit for providing a negative voltage is provided. in use. As an example, a thyristor rectifier circuit or a switching regulator is used as a positive voltage regulator circuit, and a transistor dropper circuit is used as a negative voltage regulator circuit.

Note that Patent Documents 1 and 2 below are examples of prior art documents that describe a circuit that performs power control on a superconducting coil.
JP-A 64-9605 JP-A-6-327171

  However, if two regulator circuits such as a positive voltage regulator circuit and a negative voltage regulator circuit are used to realize a bipolar power supply, the configuration of the power supply becomes complicated.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a superconducting coil power circuit capable of realizing a bipolar power source for a superconducting coil with a simple configuration.

  In order to solve the above-described problems, a superconducting coil power supply circuit according to the present invention is a superconducting coil power supply circuit for supplying a bipolar power supply voltage to a superconducting coil. A DC power supply unit that outputs power and a diode that is forward-connected between the DC power supply unit and the superconducting coil, converts a single-polarity DC power supply voltage into both polarities by a voltage drop action, and provides the diode to the superconducting coil. It is characterized by.

  This superconducting coil power supply circuit includes a diode connected in the forward direction between a DC power supply unit that outputs a DC power supply voltage of a single polarity and the superconducting coil. The DC power supply voltage is converted to bipolar and provided to the superconducting coil. For example, when the voltage drop of the diode is +11 [V], when it is desired to supply +10 [V] to the superconducting coil, the DC power supply voltage may be set to +21 [V], and −10 [V] to the superconducting coil. When it is desired to supply a voltage, the DC power supply voltage may be set to +1 [V]. As described above, according to the power supply circuit for a superconducting coil described above, a bipolar power supply voltage can be supplied to a superconducting coil by using a single DC power supply unit that outputs a single-polarity DC power supply voltage and a simple electric element called a diode. Therefore, a bipolar power supply for a superconducting coil can be realized with a simple configuration.

  The superconducting coil power supply circuit may further include a switch connected in parallel to the diode. As a result, when a voltage drop due to the diode is unnecessary, for example, when increasing the coil current or keeping the coil current constant, the coil current can be made to bypass the diode by closing the switch. A voltage drop due to the diode can be preferably avoided.

  In addition, the superconducting coil power supply circuit connects a first current path connecting one pole of the DC power supply unit and one end of the superconducting coil, and a first current path connecting the other pole of the DC power supply unit and the other end of the superconducting coil. Two current paths, a third current path for connecting the first current path and the second current path to return the coil current, and the diode is a connection point of the first and third current paths. And one end of the superconducting coil, and at least one of a connection point between the second and third current paths and the other end of the superconducting coil. Thus, in the superconducting coil power supply circuit having the first to third current paths, the voltage across the superconducting coil is set to a certain voltage value greater than zero, and the superconducting coil is connected to the superconducting coil via the first and second current paths. A first operation for supplying a coil current and a second operation for returning the coil current to the superconducting coil through the third current path by making the voltage across the superconducting coil close to zero are arbitrarily set by a PWM method or the like. The increase / decrease rate of the coil current can be suitably controlled in combination. In such a circuit configuration, between the connection point of the first and third current paths and one end of the superconducting coil, and between the connection point of the second and third current paths and the other end of the superconducting coil. By connecting the diode to at least one of them, the coil current passes through the diode in both the first and second operations when the coil current is reduced, and the rate of reduction of the coil current is suitably controlled. it can.

In the superconducting coil power supply circuit, the bipolar DC power supply voltage provided to the superconducting coil is within a range of ± V ₁ [V] (V ₁ > 0), and the absolute value of the diode drop voltage VF is V _It may be characterized by being ₁ [V] or more. Accordingly, when it is desired to supply the voltage V ₁ [V] to the superconducting coil, the single polarity DC power supply voltage output from the DC power supply unit is (VF + V ₁ ) [V], and −V ₁ [V] is applied to the superconducting coil. When a single-polarity DC power supply voltage output from the DC power supply unit is set to (VF−V ₁ ) [V], a bipolar power supply for a superconducting coil can be suitably realized.

  According to the power supply circuit for a superconducting coil according to the present invention, a bipolar power supply for the superconducting coil can be realized with a simple configuration.

  Embodiments of a power supply circuit for a superconducting coil according to the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a circuit diagram showing a configuration of an embodiment of a power supply circuit for a superconducting coil according to the present invention. Referring to FIG. 1, the superconducting coil power supply circuit 1 according to the present embodiment is a circuit for supplying a bipolar DC power supply voltage to the superconducting coil 2, and includes a DC power supply unit 3, a plurality of diodes 4, and a switch 5. , A capacitor 6, a positive power line 7, a negative power line 8, a reflux line 9, inductors 10a and 10b, and a filter 11.

  The superconducting coil 2 is mainly used as an electromagnet, for example, as a lifting magnet. The superconducting coil 2 is formed by winding a wiring made of a superconducting material such as niobium titanium, and its resistance value is, for example, 2000 [Ω] / 60000 [m] at room temperature and 0 [Ω] in the superconducting state. The inductance is, for example, 100 [H] to 200 [H]. The superconducting coil 2 has one end 2a electrically connected to one output end 1a of the superconducting coil power supply circuit 1, and the other end 2b electrically connected to the other output end 1b of the superconducting coil power supply circuit 1. Thus, the bipolar DC power supply voltage Vb is received from the superconducting coil power supply circuit 1.

  The DC power supply unit 3 outputs a single polarity DC power supply voltage Va (≧ 0). The DC power supply unit 3 generates a DC power supply voltage Va by converting an AC power supply voltage supplied from, for example, a three-phase AC power supply. Such a DC power supply unit 3 is preferably realized by performing three-phase full-wave rectification by a bridge circuit including a plurality of diodes, for example. Alternatively, the DC power supply unit 3 may be configured by a pure bridge circuit using a thyristor or a mixed bridge circuit using a diode and a thyristor. The DC power supply unit 3 has a positive output terminal 3a and a negative output terminal 3b, and provides the generated DC power supply voltage Va between the positive output terminal 3a and the negative output terminal 3b.

  The positive power supply line 7 is a first current path that electrically connects one pole (plus terminal) of the DC power supply unit 3 and one end of the superconducting coil 2. On the positive power supply line 7, an inductor 10 a, a plurality of diodes 4, and one coil of a filter 11 are connected in this order from the DC power supply unit 3 toward the superconducting coil 2. The negative power supply line 8 is a second current path that electrically connects the other pole (negative terminal) of the DC power supply unit 3 and the other end of the superconducting coil 2. On the negative power line 8, the inductor 10 b and the other coil of the filter 11 are connected in series in this order from the DC power supply unit 3 toward the superconducting coil 2.

  The return line 9 is a third current path for connecting the positive power line 7 and the negative power line 8 to return the coil current. One end of the reflux line 9 is electrically connected to a connection point between the DC power supply unit 3 and the inductor 10a in the positive power supply line 7 (connection point N1), and the other end of the reflux line 9 is connected to the negative power supply line. 8 is electrically connected to a connection point between the DC power supply unit 3 and the inductor 10b (connection point N2). The return line 9 is provided with a return diode (flywheel diode) 12, and the return diode 12 is connected with the connection point N1 side as a cathode and the connection point N2 side as an anode.

  The plurality of diodes 4 are connected in the forward direction between the DC power supply unit 3 and the superconducting coil 2, and convert the DC power supply voltage Va having a single polarity into a DC power supply voltage Vb having both polarities by a voltage drop action, thereby superconducting coil 2. It is an electric element for providing to. In the present embodiment, a plurality of diodes 4 are connected in series on the positive power supply line 7 with the DC power supply 3 side as an anode and the superconducting coil 2 side as a cathode. In the present embodiment, the plurality of diodes 4 are connected between the connection point N1 of the positive power line 7 and the reflux line 9 and the one end 2a of the superconducting coil 2. For example, when the plurality of diodes 4 has a drop voltage of 0.6 [V] per unit, and it is desired to obtain a voltage drop of 10 [V] or more across the plurality of diodes 4, there are 17 or more diodes 4. Connected in series.

For example, when the voltage drop of the diode is +11 [V], when it is desired to supply the DC power supply voltage Vb of +10 [V] to the superconducting coil 2, the DC power supply voltage Va may be set to +21 [V]. When it is desired to supply the DC power supply voltage Vb of −10 [V] to the DC power supply voltage Va, the DC power supply voltage Va is set to +1 [V]. That is, when the bipolar DC power supply voltage Vb to be provided to the superconducting coil 2 is within a range of ± V ₁ [V] (V ₁ > 0), the absolute value of the drop voltage of the plurality of diodes 4 is expressed as V ₁ [ V] or higher. In this case, the DC power supply voltage Va output from the DC power supply 3 when you want to supply the DC power supply voltage Vb of _V 1 [V] to the superconducting coil 2 and _{(VF + V 1) [V} ], -V 1 the superconducting coil 2 When it is desired to supply the DC power supply voltage Vb of [V], the bipolar power supply for the superconducting coil is suitably realized by setting the DC power supply voltage Va output from the DC power supply unit 3 to (VF-V ₁ ) [V]. it can.

  In the present embodiment, the plurality of diodes 4 are connected between the connection point N1 of the positive power supply line 7 and the reflux line 9 and the one end 2a of the superconducting coil 2. You may connect between the connection point N2 of the line 8 and the reflux line 9, and the other end 2b of the superconducting coil 2. In this case, the plurality of diodes are connected in series on the negative power supply line 8 with the superconducting coil 2 side as an anode and the DC power supply unit 3 side as a cathode. Further, in the present embodiment, a plurality of diodes 4 are connected between the DC power supply unit 3 and the superconducting coil 2, but the present invention is not limited to a plurality, and only a single diode 4 may be connected.

  The switch 5 is a mechanical switch connected in parallel to a part of the plurality of diodes 4 (that is, in series with respect to the other diodes 4). When the superconducting coil power supply circuit 1 is operated, voltage drops due to the plurality of diodes 4 are sometimes unnecessary or desired to be reduced. For example, when the coil current is increased or when it is desired to keep the coil current constant. In such a case, by closing the switch 5, a coil current can be caused to bypass all or a part of the diodes 4, and a voltage drop due to the diodes 4 can be suitably avoided / reduced.

  The operation of the superconducting coil power supply circuit 1 having the above configuration will be described. FIG. 2A is a graph showing the change over time of the coil current flowing through the superconducting coil 2. FIG. 2B is a graph showing a change with time of the DC power supply voltage Vb applied to both ends 2a and 2b of the superconducting coil 2. FIG. As shown in FIGS. 2A and 2B, the superconducting coil power supply circuit 1 operates in a period A in which the coil current is increased, a period B in which the coil current is kept constant, and a decrease in the coil current. It consists of period C.

但し、Ｌはコイルのインダクタンス、ｔは時間、Ｒはコイルの抵抗値である。 In the period A, the superconducting coil power supply circuit 1 applies a positive predetermined voltage V ₁ [V] to both ends 2 a and 2 b of the superconducting coil 2 as shown in FIG. Here, there is generally the following relationship between the both-end voltage V applied to the coil and the coil current I.

Here, L is the inductance of the coil, t is the time, and R is the resistance value of the coil.

In the case of a superconducting coil, since the resistance value is so small that it can be ignored, the voltage V between both ends can be approximated only by the first term on the right side of the above equation (1). Therefore, when a positive predetermined voltage V ₁ [V] is applied to both ends 2a, 2b of the superconducting coil 2, V ₁ / L ₁ (L ₁ : inductance of the superconducting coil 2) has a constant change rate with a proportional coefficient. The coil current increases (see FIG. 2A). In this period A, it is preferable to bypass a part of the plurality of diodes 4 by the coil current by closing the switch 5. This is because a large voltage drop in the plurality of diodes 4 causes extra power consumption and heat generation. The reason why only a part of the plurality of diodes 4 is bypassed is to facilitate the current control by suppressing the time constant τ (= L / R) of the circuit. May be bypassed (that is, the switch 5 may be connected in parallel to all of the plurality of diodes 4).

As described above, the rate of change of the coil current is determined by V ₁ / L ₁ , but this rate of change can be changed to an arbitrary level by controlling the voltage across the superconducting coil 2 by the PWM method. That is, the arrows voltage across the superconducting coil 2 and V _1, the DC power supply unit 3, the positive side power source line 7, the superconducting coil 2, the negative power supply line 8, and illustrated in the coil current (FIG. 1 in order of the DC power source 3 I ₁ ) and the voltage across the superconducting coil 2 are brought close to zero, and the coil current in the order of the superconducting coil 2, the negative power supply line 8, the reflux line 9, the positive power supply line 7, and the superconducting coil 2. The effective coil current change rate can be suitably controlled by controlling the time width of each operation while alternately performing the second operation for refluxing (arrow I ₂ shown in FIG. 1).

  Next, as shown in FIG. 2A, when the magnitude of the coil current reaches a predetermined value Ia, the period B is started. In the period B, the superconducting coil power supply circuit 1 maintains the coil current at a constant value Ia by setting the voltage across the superconducting coil 2 to zero. In this period B, in order to prevent unnecessary power consumption, it is preferable to close part of the plurality of diodes 4 to the coil current by closing the switch 5.

Subsequently, the superconducting coil power supply circuit 1 moves to an operation of reducing the coil current to zero (period C). In period B, the superconducting coil power supply circuit 1 applies a negative predetermined voltage −V ₁ [V] to both ends 2 a and 2 b of the superconducting coil 2 as shown in FIG. When a negative predetermined voltage −V ₁ [V] is applied to both ends 2 a and 2 b of the superconducting coil 2, the coil current decreases with a constant rate of change with −V ₁ / L ₁ as a proportional coefficient (FIG. 2A )reference). In this period C, the plurality of diodes 4 are passed through the coil current by opening the switch 5, and a negative predetermined voltage −V ₁ [V] is generated by a voltage drop in the plurality of diodes 4.

In the period C, the voltage across the superconducting coil 2 may be controlled by the PWM method as in the period A. That is, the voltage between both ends of the superconducting coil 2 is set to −V ₁ , the DC power supply unit 3, the positive power supply line 7 (including a plurality of diodes 4), the superconducting coil 2, the negative power supply line 8, and the DC power supply unit 3 in this order. A first operation for flowing a coil current, a voltage across the superconducting coil 2 is brought close to zero, a superconducting coil 2, a negative power supply line 8, a return line 9, a positive power supply line 7 (including a plurality of diodes 4), and By controlling the time width of each operation while alternately performing the second operation for returning the coil current in the order of the superconducting coil 2, the effective change rate of the coil current can be suitably controlled.

  It is as follows when the effect which power supply circuit 1 for superconducting coils concerning this embodiment has is put together. When reducing the coil current flowing through the superconducting coil 2, most of the load is an inductance, and therefore a voltage having a polarity opposite to that of the coil current must be applied. A conventional superconducting coil power supply circuit includes a regulator circuit for providing a positive voltage to the superconducting coil and another regulator circuit for providing a negative voltage. If two regulator circuits are provided, there is a problem that the configuration becomes complicated.

  On the other hand, the superconducting coil power supply circuit 1 according to the present embodiment is forward-connected between the DC power supply unit 3 that outputs a single polarity DC power supply voltage Va, and the DC power supply unit 3 and the superconducting coil 2. A plurality of (or may be single) diodes 4 are provided, and the DC power supply voltage Va having a single polarity is converted into both polarities and provided to the superconducting coil 2 by the voltage drop action of the diodes. That is, since the DC power supply unit 3 has a single polarity, the DC power supply unit 3 can be configured by a single regulator circuit. In the superconducting coil power supply circuit 1, a simple electric element called a diode is added to the DC power supply unit 3 to reverse the coil current. A polar power supply voltage is achieved. Therefore, according to the power supply circuit 1 for a superconducting coil according to the present embodiment, a bipolar power supply for a superconducting coil can be realized with a simpler configuration than the conventional circuit.

  Although a voltage drop can also be realized by providing a resistance element instead of a diode, for an element such as a resistance element whose drop voltage changes according to the current, as shown in FIG. It is difficult to keep the reduction rate of the coil current constant. That is, as the coil current decreases, the voltage drop also decreases. Therefore, it takes a long time until the coil current becomes zero after the coil current decreases. Further, if the resistance value is increased by shortening this time, an excessive voltage drop occurs immediately after the start of the decrease of the coil current, and the coil current is rapidly decreased. According to the superconducting coil power supply circuit 1 according to the present embodiment, since the reduction rate of the coil current is kept constant by using a diode having a substantially constant voltage drop, immediately after the start of the reduction of the coil current and the coil The coil current can be suitably reduced in both the period from when the current becomes sufficiently small until it becomes completely zero.

  The superconducting coil power supply circuit according to the present invention is not limited to the above-described embodiment, and various other modifications are possible. For example, in the above-described embodiment, the configuration including the third current path (return line 9) in addition to the first and second current paths (positive power supply line 7, negative power supply line 8) is exemplified. Even if it is the structure which is not provided with this electric current path | route, the effect of this invention can be acquired suitably.

It is a circuit diagram which shows the structure of one Embodiment of the power supply circuit for superconducting coils by this invention. (A) It is a graph which shows the time change of the coil current which flows into a superconducting coil. (B) It is a graph which shows the time change of the DC power supply voltage applied to the both ends of a superconducting coil.

Explanation of symbols

  Va: Single polarity DC power supply voltage, Vb: Bipolar DC power supply voltage, 1 ... Superconducting coil power supply circuit, 2 ... Superconducting coil, 3 ... DC power supply unit, 3a ... Positive side output terminal, 3b ... Negative side output Terminal: 4 ... Diode 5 ... Switch 6 ... Capacitor 7 ... Positive side power line 8 ... Negative side power line 9 ... Reflux line 10a, 10b ... Inductor 11 ... Filter 12 ... Reflux diode

Claims (4)

A power supply circuit for a superconducting coil for supplying a bipolar DC power supply voltage to the superconducting coil,
A DC power supply unit that outputs a single polarity DC power supply voltage;
A diode that is forward-connected between the DC power supply unit and the superconducting coil, and converts the single-polarity DC power supply voltage into a bipolar polarity by a voltage drop action and provides the diode to the superconducting coil. A superconducting coil power supply circuit.   The power supply circuit for a superconducting coil according to claim 1, further comprising a switch connected in parallel to the diode. A first current path connecting one pole of the DC power supply unit and one end of the superconducting coil;
A second current path connecting the other pole of the DC power supply unit and the other end of the superconducting coil;
A third current path for connecting the first current path and the second current path to recirculate the coil current;
The diode is connected between the connection point of the first and third current paths and one end of the superconducting coil, and between the connection point of the second and third current paths and the other end of the superconducting coil. The power supply circuit for a superconducting coil according to claim 1, wherein the power supply circuit is connected to at least one of them. The bipolar DC power supply voltage provided to the superconducting coil is within a range of ± V ₁ [V] (V ₁ > 0), and the absolute value of the voltage drop of the diode is V ₁ [V] or more. The power supply circuit for a superconducting coil according to any one of claims 1 to 3, wherein

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