JP2735738B2 - Superconducting coil quench detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a quench (normal conduction transition) of a superconducting coil which is excited by a chopper circuit.

[0002]

2. Description of the Related Art FIG. 5 shows, for example, "C3-19 Toroidal SM"
FIG. 11 is a configuration diagram showing a conventional superconducting coil quench detection device that excites by a chopper circuit described in "ES Principle Demonstration System, Method of Detecting Normal Conduction Transition During Chopper Excitation". In the figure, 1 is an inverter circuit, 2 is a smoothing capacitor connected to the DC output side of the inverter circuit 1, 3
Is a chopper circuit, 4 is a circulating diode as circulating current flowing means, 5 is a circuit breaker, 6 is a protection resistor, 7 is a superconducting coil, and 8 is a boxcar integrator as voltage extracting and storing means. The boxcar integrator 8 includes a boxcar circuit 9
A signal terminal S for inputting a voltage generated in the superconducting coil 7 , a trigger pulse terminal T for inputting a trigger pulse from the chopper 2, and an output terminal G for monitoring a gate signal. doing. 11 is a meter relay, 12 is an oscilloscope for monitoring the waveform of the boxcar integration circuit 8, and the inverters 1 to 12 are connected as shown.

Next, the operation will be described with reference to FIG. 5 and FIGS. The three-phase AC voltage of the system is converted into a DC voltage by the inverter circuit 1. This DC voltage is chopped by the chopper circuit 2 and applied to the superconducting coil 7 as a continuous voltage pulse.

FIG. 6 is a schematic diagram of the excitation by the chopper circuit shown in FIG. As shown in the figure, a continuous pulse of 400 [V] and several hundred microseconds is applied to the superconducting coil 7. Each time a pulse is applied, the current flowing in the superconducting coil increases stepwise, and a pulse voltage of a narrow width continues to be applied to compensate for current decay due to circuit loss even when the maximum current is maintained.

In the superconducting state, since the electric resistance is zero and a large current can flow without any loss, a large current is caused to flow in the superconducting coil to generate a high magnetic field, which is used as a high magnetic field generator. The stored energy of the superconducting coil is given by the following equation, and the stored energy increases as the current value increases. Energy holding = (1/2) x (inductance) x
(Square of electric current) Using this fact, the use of a superconducting coil as an electromagnetic energy storage device has been studied.

However, since a large current flows through the superconducting coil and a large amount of energy represented by the above equation is accumulated, when the superconductivity is broken (quenched) and transitions to normal conduction, the initial minute voltage is reduced. If the energy stored in the superconducting coil is not taken out immediately after the detection, the stored energy is consumed in the coil, which may lead to a burnout of the superconducting coil. The quench detection voltage of the superconducting coil by a normal DC power supply is 100 [mV] to 1 [V].

On the other hand, in the case of chopper excitation, a high voltage pulse voltage (400 V in this example) is repeatedly applied as shown in FIG. It is difficult to detect mV] with high accuracy, and in order to solve this problem, a boxcar integrator 8 is used as a measuring instrument.

Next, the operation of the conventional quench detection device using the boxcar integrator 8 will be described with reference to the operation principle diagram of FIG. The boxcar circuit 9 of the boxcar integrator 8 is triggered by a repetitive signal supplied from the chopper 3 via the terminal T, and the time when the trigger signal is issued, that is, the time t1 when the voltage pulse applied to the superconducting coil 7 falls. At times t2 and t5 at which no voltage pulse is applied after a predetermined time TD from t4 and t4, a gate open signal is issued to extract the voltage of the superconducting coil 7 and store it as a storage voltage. Then, the memory voltage at that time is integrated by the integration circuit 10, and
A voltage corresponding to the stored voltage is output to the meter relay 11.

As described above, since the voltage of the superconducting coil when the voltage is not applied to the superconducting coil 7 is extracted, if the superconducting coil 7 has no abnormality (quench), the extracted voltage and the stored voltage Is almost zero volts. Further, since the extracted voltage is integrated by the integration circuit 10 and output to the meter relay 11, the influence of the noise when the extracted voltage is mixed with the noise is reduced.

Therefore, when a quench occurs in the superconducting coil by adopting the circuit configuration as shown in FIG.
An output proportional to the minute voltage can be obtained without being affected by the applied voltage from the chopper circuit.If the output voltage exceeds the set value, it is determined to be quench, and the meter relay 11 is activated to activate the circuit breaker. 5 is opened, the energy held by the superconducting coil is consumed by the external protection resistor 6, and the superconducting coil 7 can be maintained in a healthy state.

[0011]

The conventional quench detection device for a superconducting coil is configured as described above.
Even when the chopper circuit is excited, if the current of the superconducting coil is maintained at a predetermined value, it is possible to detect the generation of a minute voltage by the above-described operation principle. However, quench detection when the coil current changes has the following problems.

As described above, while the voltage pulse is being applied to the superconducting coil, the current of the superconducting coil increases. On the other hand, while no voltage pulse is applied, the circulating diode 4 of the chopper circuit is conductive, and the current flowing through the superconducting coil flows back through the circulating diode 4. Since a semiconductor element generally has a forward resistance, the excitation schematic diagram shown in FIG. 6 becomes a voltage schematic diagram of FIG. 8 and a current schematic diagram of FIG. 9 in consideration of the forward resistance. That is, when the current is flowing between the superconducting coil 7 and the circulating diode 4, a negative voltage corresponding to the forward voltage drop of the circulating diode 4 is applied to both ends of the superconducting coil 7, and the current attenuates. . Also, as the current increases, the forward voltage drop increases.

Therefore, when the current value is constant, the forward voltage drop is also constant, and it is possible to detect the generation of a minute voltage due to the quench of the superconducting coil by the method shown in the above-mentioned conventional example. However, when the current value changes, the voltage in the sampling region where no pulse voltage is applied also changes, making it difficult to detect quench.

The present invention has been made in order to solve such a problem, and a quench of a superconducting coil capable of accurately detecting a small voltage generated due to a quench (normal conduction transition) of a superconducting coil excited by a chopper circuit. It is intended to obtain a detection device.

[0015]

A superconducting coil quench detection apparatus according to the present invention is provided with a circuit in which a voltage is intermittently applied by a chopper circuit to be excited, and when no voltage is applied, a circulating current flowing means is provided. The respective voltages of the first and second coils of the superconducting coil, through which a circulating current can flow, are respectively extracted by the first and second voltage extraction and storage means a predetermined time after receiving a signal from the chopper circuit. Then, the difference between the stored voltages is calculated by a subtraction means.

[0016]

According to the present invention, the first and second voltage extracting and storing means extract the voltages of the first and second coils after a predetermined time from receiving the signal from the chopper circuit. The voltage of each coil when no voltage is applied can be extracted. Therefore, the extracted and stored storage voltage is not affected by the voltage applied from the chopper circuit. Further, the first means
And the difference between the stored voltages stored by the second voltage extracting and storing means is calculated, so that the changing voltage drops of the circulating current flowing means cancel each other out and are affected by the voltage generated in the circulating current flowing means. It is possible to detect a minute voltage generated in the superconducting coil without detecting the voltage.

[0017]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the drawing, reference numeral 20 denotes a superconducting coil, and a first coil 21 and a second coil 22 having substantially equal inductances are connected via an intermediate point C. They are connected in series, and are wound continuously and structurally in an integrated manner. Reference numerals 23 and 24 denote first and second boxcar integrators, which are exactly the same as the boxcar integrator 8 in the conventional apparatus.
Boxcar circuit 9 and integrator 10 as voltage extraction and storage means
And the terminal voltages of the first and second coils are input to the respective signal terminals S. Reference numeral 25 denotes a subtractor as a subtraction means, which calculates the difference between the outputs of the first and second boxcar integrators 23 and 24 and outputs the result to the meter relay 11. Other configurations are the same as those of the conventional device shown in FIG. 5, and the same or corresponding components are denoted by the same reference characters and description thereof is omitted.

Next, the operation will be described. With the circuit configuration as shown in FIG. 1, the forward voltage generated in the circulating diode 4 of the chopper circuit can be applied to the boxcar circuit 9, the integrating circuit 10 of the first boxcar integrator 23, and the second boxcar integrator. 24 boxcar circuits 9, integration circuits
10 have the same effect, and are canceled by the subtractor 25 . Therefore, only the minute voltage due to the quench generated in the first and second coils on the positive side or the negative side from the intermediate point C can be detected as the output of the subtracter 25 .

Embodiment 2 FIG. In the above-described embodiment, the case where the first and second coils are structurally integrated has been described. However, two structurally independent superconducting coils 31 and 32 having substantially the same inductance and conducting current are described. Are excited in series, as shown in the block diagram of FIG. 2, the voltages of the first and second coils 31 and 32 constituting the superconducting coil 30 are each subtracted after signal processing by a boxcar integrator. Similarly, the quench generated in the superconducting coil can be detected with high accuracy.

Embodiment 3 FIG. When the two coils 31, 32 are separately excited by the first and second chopper circuits 41, 42, as shown in the configuration diagram of FIG. By performing the subtraction after the signal processing by the Kerr integrators 23 and 24, the quench generated in the superconducting coil can be similarly detected with high accuracy.

Embodiment 4 FIG. Further, since a measuring device such as a boxcar integrator generally does not have a high withstand voltage characteristic, a voltage is clipped in front of the boxcar integrator as shown in the configuration diagram of FIG. 4 to protect the measuring device. Voltage clippers 51 and 52 to be inserted into the boxcar integrators 23 and 24 by clipping the input voltage as shown on the left of the voltage clipper 51 to a predetermined voltage as shown by a solid line on the right. desirable.

Although each of the above embodiments uses a diode as the circulating current flowing means, it may use a thyristor, a transistor, or the like.
Although the superconducting coil has the first and second coils, even if it has three or more coils, the voltages of these coils are extracted and stored, and the values are appropriately combined and subtracted. By doing so, a similar effect is achieved.

Further, in the above embodiment, the voltage extraction and storage means is based on a boxcar circuit, and the subtraction means is a subtractor. However, the same operation may be performed by a microcomputer or the like.

[0024]

As described above, according to the present invention, the first
And the voltage of the second coil is extracted and stored, and a difference between the stored voltages is obtained.
It is possible to accurately detect a minute voltage change generated in the superconducting coil without being affected by the voltage drop of the circulating current flowing means.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a quench detection device for a superconducting coil according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram showing a quench detection device for a superconducting coil according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a quench detection device for a superconducting coil according to Embodiment 3 of the present invention.

FIG. 4 is a configuration diagram showing a quench detection device for a superconducting coil according to Embodiment 4 of the present invention.

FIG. 5 is a configuration diagram showing a conventional quench detection device for a superconducting coil.

FIG. 6 is a schematic diagram of excitation by a chopper circuit.

FIG. 7 is an operation principle diagram of quench detection by a boxcar integrator.

FIG. 8 is a schematic diagram of a voltage for excitation by a chopper circuit.

FIG. 9 is a schematic diagram of an excitation current by a chopper circuit.

[Explanation of symbols]

 3, 41, 42 Chopper circuit 4 Circulating diode 9 Boxcar circuit 10 Integrator 20, 30 Superconducting coil 21, 31 First coil 22, 32 Second coil 23 First boxcar integrator 24 Second boxcar Integrator 25 Subtractor

Claims (1)

(57) [Claims] 1. A quench detection device for a superconducting coil having first and second voltage extracting and storing means and a subtracting means, wherein the superconducting coil has a first coil and a second coil, Each coil is configured so that a voltage is intermittently applied by a chopper circuit to be excited and a circulating current can flow through a circulating current circulating means when the voltage is not applied. The voltage extraction storage means is for extracting a voltage of the first coil a predetermined time after receiving a signal from the chopper circuit and storing the voltage as a first storage voltage, wherein the second voltage extraction storage Means for extracting a voltage of the second coil a predetermined time after receiving a signal from the chopper circuit and storing the voltage as a second storage voltage; and wherein the subtraction means stores the first storage voltage. Electric A quench detection apparatus of the superconducting coil difference is to operation of said second storage voltage.