JPH0738335B2 - Excitation device for superconducting coil - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting coil excitation device for demagnetizing a coil of a superconducting pulse magnet.

2. Description of the Related Art Since a superconducting coil has a resistance value of 0, it can pass a current without being attenuated. Therefore, excitation with a fast rise is easy, and it is effective as a means for instantaneously obtaining a strong magnetic field. Development of magnetic field generators and power storage systems for sealing high-temperature plasma in fusion reactors inside the reactor is underway.

FIG. 3 is a block schematic diagram of a conventional superconducting coil exciter.

In FIG. 3, 1 is a superconducting coil, 2 is a resistor, 3 is a switch, 4 is a power source for supplying an exciting current to the superconducting coil 1, and 5 is a current detection for detecting the value of the current flowing through the superconducting coil 1. It has a current-voltage conversion gain of Ka [V / A]. Reference numeral 6 is a command generating means for generating a current value to be passed through the superconducting coil 1, and 7 is power supply controlling means for controlling the power supply 3 in accordance with the difference between the output of the command generating means and the output of the current detecting means 4. The transfer function F (s) is F
(S) = K ₁ · (s + b) / (s + a). here,
s is a plasma operator. Reference numeral 8 is a quench detecting means for detecting that the superconducting coil 1 is quenched due to a temperature rise, an external magnetic field, or the like, that is, the superconducting state is broken and the resistance value starts.

The operation of the conventional superconducting coil exciting device configured as described above will be described in more detail.

When the superconducting coil 1 is in the excitation mode, the switch 3 is closed and the command generating means 6 generates a step-shaped target current value. The power supply control means 7 outputs a control voltage signal according to the target current value, and the power supply 4 outputs the superconducting coil 1.
Voltage is applied to. Along with this, the current detecting means 5 detects the value of the current flowing through the superconducting coil 1 and forms a negative feedback loop so that it matches the target current value.

The voltage-to-current transfer characteristic of the superconducting coil has a perfect integral characteristic 1 / (Ls) due to only the inductance component of the coil because the resistance value is 0. Therefore, when the exciting current of the superconducting coil reaches the target value, the voltage supplied by the power supply 4 becomes zero. A state in which a constant current flows at this voltage 0 is called a permanent current state.

In this permanent current state, when the superconducting coil 1 is quenched, the permanent current causes the superconducting coil 1 to abnormally heat due to Joule loss, and in the worst case, burns or burns out. The quench detecting means 8 detects that the superconducting coil 1 starts to have a resistance value by using a bridge circuit or the like, and opens the switch 3. As a result, the exciting current is rapidly attenuated in the resistor 2 and the burnout of the superconducting coil 1 is prevented.

As described above, the superconducting coil exciter in which the resistor 2 is always connected in parallel to the superconducting coil is common. (For example, JP-A-58-4906).

Problems to be Solved by the Invention However, the above-described exciting device for the superconducting coil has the following problems.

The load impedance of the power source 5 including the resistor 2 is (R +
sL) / (sRL). Here, R is the resistance value of the resistor 2.

At this time, the closed loop transfer function G (s) of the superconducting coil exciter as described above is given by the following equation.

Given in. However, A = (a + G / L) / R / (R +
G) + b ・ G / (R + G), B = G ・ b / L ・ R / (R + G)
Is. Here, L is the inductance of the superconducting coil 1, G ₀ = Ka · K ₁ .

FIG. 4 is a waveform diagram showing the unit step response of G (s), and the response value is standardized by the target value. Figure 4 (a)
As shown in, since the denominator of the equation (1) has a second-order lag form, it may overshoot the target value.
Due to this overshoot, there is a problem that it is easy to quench by exceeding the critical current of the superconducting coil. Further, if the braking of G (s) is increased as shown in FIG. 4 (b) in order to suppress this overshoot, there is a problem that the convergence time to the target value becomes long.

In other words, the braking of the control system and the rising time are in a relationship of front and back, and are not compatible. This is because in a system with large braking, it is necessary to increase the response frequency of the system in order to accelerate the rise time, and for this purpose, it is necessary to increase the gain K _{1 of the} controller. This is because when the gain of the controller is increased, there is a problem that it may malfunction due to noise or that it may not operate as designed due to the limitation of the operating range of the controller.

Further, even in the excitation mode, since the resistors are connected in parallel, the Joule loss of this resistor is large.

Means for Solving the Problems In order to solve the above problems, the superconducting coil exciting device of the present invention is a superconducting coil, a power supply for supplying voltage and current to the superconducting coil, and a current flowing through the superconducting coil. A current detecting means for detecting a quantity, a command generating means for outputting a first target value or a second target value, and the power source according to the difference between the output of the target generating means and the output of the current detecting means. A power supply control means for controlling, a resistor connected in parallel to the superconducting coil, a switching means connected in series with the resistor, and a predetermined value between the first target value and the second target value. Switching control means for detecting that the output value of the current detection means has reached the value and controlling conduction of the switching means.

Action According to the present invention, since the resistor is connected in parallel to the superconducting coil immediately before the overshoot, the present invention can prevent quenching. Further, the overshoot amount itself can be reduced and the target value can be reached at high speed.

Embodiment Hereinafter, a superconducting coil exciter according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic block diagram of an exciting device for a superconducting coil according to the present invention. 1 is a superconducting coil, 2 is a resistor, 3 is a first switch, 4 is a power supply, 5 is a current detection means, 7 is a power supply control means, and 6 is a command for outputting a first target value or a second target value. Generation means, 8 is quench detection means, 9 is a second switch, 10 is the output value of the current detection means 6 reaches a predetermined value between the first target value and the second target value. Second switch 9
Is a switching control means for opening and closing. In FIG.
Since the superconducting coil 1, the resistor 2, the first switch 3, the power source 4, the current detecting means 5, the power source controlling means 7 and the quench detecting means 8 are the same as those in the conventional example shown in FIG. 3, detailed description will be given here. Omit it.

Now, the operation of the exciting device for the superconducting coil of the present invention configured as described above will be described in more detail. FIG. 2 is a signal waveform diagram showing operation waveforms of respective parts of the superconducting coil exciting device of the present invention, and FIGS. 2 (a) to 2 (c) are points A to C in FIG. Corresponding to.

First, the case of exciting the superconducting coil 1 will be described. At this time, the second switch 9 is open and the first switch 3 is closed. The command generating means 6 also generates a step-like target current signal A (target value I ₀ ). The power supply control means 7 outputs a control voltage signal in response to the target current signal A, and the power supply 4 applies a voltage to the superconducting coil 1. At the same time, the current detecting means 5 detects the value of the current flowing through the superconducting coil 1 and configures a negative feedback loop so that it matches the target current signal A. The transfer function G '(s) of this negative feedback loop is Given in. However, A '= (a + G / L), B' = Gb /
It is L.

Now, the switching control means 10 outputs the switching signal C when the exciting current of the superconducting coil 1 reaches 0.9I ₀ (90% of the target value). In response to this switching signal C, the second
Switch 9 is closed. The transfer function G ″ (s) of the negative feedback loop at this time is Given in. However, A ″ = (a + G / L) ・ R / (R +
G) + b ・ G / (R + G), B ″ = G ・ b / L ・ R / (R +
G).

Therefore, it becomes the same as G (s) in the equation (1),
In the equations (1) ′ and (2), A ″ = A ′ · R /
(R + G) + b ・ G / (R + G), B ″ = B ′ · R / (R +
G) is established.

Here, if b ≧ a + G / L (3), it is possible to satisfy A ′ ≧ A ″.
Comparing the equations (1) and (2), when A ′ ≧ A ″, the braking of G ′ (s) becomes larger than that of G (s). Also, since B ″> B ′, G The response frequency of '(s) is larger than the response frequency of G (s), and a quick rising is possible. That is, in this embodiment, the resistor 2
Acts as a braking resistor.

Therefore, the excitation of the superconducting coil 1 can be speeded up, and the overshoot of the exciting current can be suppressed to be small. Furthermore, it is possible to prevent quenching of the superconducting coil 1 due to this overshoot. In addition, the current flowing through the superconducting coil 1 is equal to the target value.
The braking resistor 2 is connected before reaching I ₀ . Therefore, the detection sensitivity Ka of the current detection means 5
Even if the variation occurs, if the threshold value of the switching control means 10 is set outside the variation range, the variation of the current detection means 5 does not cause the switching control means 10 to malfunction.

Now, when the exciting current reaches a steady value, the quench detecting means 8 monitors the voltage across the superconducting coil 1 and the like. When the superconducting coil 1 is quenched, the quench detecting means 8 opens the first switch 3 so that the exciting current is consumed by the resistor 2 to prevent the superconducting coil 1 from burning or burning.

When demagnetizing the superconducting coil, the exciting current is
When the initial value falls below about 90%, the second switch 9
open.

The condition of the equation (3) can be easily realized by reducing the gain K ₁ of the power supply control means 7 or the gain Ka of the current detection means 5.

Further, in the above embodiment, the resistor is also used as the quench protection resistor, but a dedicated attenuation resistor and quench protection resistor may be separately provided and connected in parallel.

Further, in the stable constant current mode, the second switch 9 is in the conducting state, but at this time, the second switch 9 may be in the disconnecting state.

In addition, it is needless to say that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.

EFFECTS OF THE INVENTION As described above, according to the present invention, since a resistor for braking is not connected in the excitation / demagnetization of the superconducting coil, high-speed excitation / demagnetization is possible and the exciting current of the superconducting coil 1 is increased. Because the resistors are connected in parallel before reaching the target value,
It is possible to suppress the transient overshoot of the exciting current to be small. Therefore, quenching due to overshoot of the exciting current of the superconducting coil can be prevented in advance. Further, since the resistor is not connected in most of the section in the excitation mode, it has an excellent characteristic that the Joule loss of the resistor can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an exciting device for a superconducting coil according to the present invention, FIG. 2 is a signal waveform diagram of each part of the exciting device for a superconducting coil according to the present invention, and FIG. 3 is a schematic block diagram for an exciting device for a conventional superconducting coil. Figure 4 shows the transfer function G (s)
It is a waveform diagram of a unit step response of. 1 ... Superconducting coil, 2 ... Resistor, 4 ... Power supply, 5 ...
... current detecting means, 6 command generating means, 7 power supply controlling means, 9 second switch, 10 switching control means.

Claims (2)

[Claims] 1. A superconducting coil, a power supply for supplying voltage and current to the superconducting coil, current detecting means for detecting the amount of current flowing through the superconducting coil, and a first target value or a second target value. Command generating means for outputting, power source control means for controlling the power source according to the difference between the output of the target generating means and the output of the current detecting means, a resistor connected in parallel to the superconducting coil, and the resistor. The switching means connected in series with the switching device, and detecting that the output value of the current detecting means reaches a predetermined value between the first target value and the second target value, and switching the switching means. An exciter for a superconducting coil, comprising: switching control means for controlling conduction. 2. The exciting device for a superconducting coil according to claim 1, wherein the power supply control means switches the circuit gain in synchronization with the conduction control of the switching means by the switching control means. .