JPH065647B2 - Superconducting coil monitor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a superconducting coil monitoring device, and more particularly to a superconducting coil monitoring device capable of detecting a normal conduction transition of a superconducting coil excited by an AC power source with good response. Regarding

[Technical background of the invention and its problems]

Recently, various superconducting wires with low AC loss have been developed, and superconducting coils that are excited by AC are being put to practical use. Thus, even when the superconducting coil is excited by alternating current, it is still necessary to take appropriate measures immediately when the superconducting coil is quenched (transition to normal conduction). Appropriate treatment during quenching can be realized by detecting the occurrence of quenching with high responsiveness. However, in the case of AC excitation, a voltage that constantly changes is generated at both ends of the superconducting coil, so quenching cannot be detected by the same method as in the case of DC excitation. For this reason, the emergence of a monitoring device that can detect a quench with high response under AC excitation is strongly desired.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a superconducting coil monitoring device that can detect a quench of a superconducting coil excited by an alternating current with good response and that has a simple structure. Especially.

[Outline of Invention]

According to the present invention, the voltage detection means for detecting the voltage across the superconducting coil excited by the AC power supply, the current detection means for detecting the current flowing in the superconducting coil, and the voltage obtained by the voltage detection means. There is provided a superconducting coil monitoring device provided with a phase determining means for outputting a signal when the phase difference between the signal and the current signal obtained by the current detecting means is π / 2 or less.

〔The invention's effect〕

The following relationship exists between the voltage signal obtained by the voltage detecting means and the current signal obtained by the current detecting means. That is, when the superconducting coil is in a perfect superconducting state, a phase difference of π / 2 exists between the voltage signal and the current signal. On the other hand, when the superconducting coil is quenched, a resistance component appears in the superconducting coil, and the presence of this resistance component causes the phase difference between the voltage signal and the current signal to be π / 2 or less. Therefore, if the phase difference determination means is provided as in this device, when the superconducting coil is quenched, that is, when the phase difference between the voltage signal and the current signal becomes π / 2 or less, the above phase difference determination is performed. A signal can be output from the means, and this signal can be used to take appropriate quench measures. In this case, the voltage across the superconducting coil and the current flowing through the superconducting coil are detected, and quench detection is performed using both detection signals, so it is necessary to perform special processing on the superconducting coil. There is no such thing, and the entire device does not become complicated.

Example of Invention

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit configuration diagram of a monitoring device according to an embodiment of the present invention.

In the figure, 1 is a superconducting coil, and this superconducting coil 1 is housed in a cryostat 2 together with liquid helium. Both ends of the superconducting coil 1 are connected to one ends of lead wires 3a and 3b formed of normal conducting wires, and the other ends of these lead wires 3a and 3b are guided to the outside of the cryostat 2 and thyristors 4a and 4b. Are connected to the output end of the AC power supply 7 via a semiconductor switch 5 and a mechanical switch 6 which are connected in antiparallel.
The thyristors 4a and 4b are controlled by the gate circuit 8 so that an alternating current can flow through the superconducting coil 1 with the superconducting coil 1 as a load. The gate circuit 8 is controlled by the gate drive circuit 9. The gate drive circuit 9 is configured to stop its operation when a signal of logical value "1" is given to the control end.

Then, at both ends of the superconducting coil 1, lead wires 10a,
One ends of the lead wires 10a and 10b are connected to one another, and the other ends of the lead wires 10a and 10b are guided to the outside of the cryostat 2 and connected to the input end of the isolation amplifier 11. Further, a current detector 12 for detecting a current flowing through the superconducting coil 1 is inserted in the middle of the lead wire 3b connecting the superconducting coil 1 and the semiconductor switch 5, and the output of the current detector 12 is isolated. It is introduced into the input terminal of the amplifier 13. The outputs of the isolation amplifiers 11 and 13 are introduced into comparators 14 and 15, respectively. The comparators 14 and 15 are configured to output rectangular wave signals E and I, respectively, during the positive half-wave period of the input signal. The output signal E of the comparator 14 is directly introduced to one input end of the EX-OR circuit (exclusive OR circuit) 16 and to the other input end of the same circuit 16 via the delay element 17, and It is introduced to one input terminal of the EX-OR circuit 18. Further, the output signal I of the comparator 15
Is introduced directly into one input end of the EX-OR circuit 19, introduced into the other input end of the same circuit 19 via the delay element 20, and further introduced into the other input end of the EX-OR circuit 18. ing.

The output signals of the EX-OR circuits 16 and 19 are introduced into the reference signal generators 21 and 22, respectively. When the signals are introduced from the EX-OR circuits 16 and 19, the reference signal generators 21 and 22 count the 1 MHz clock pulse output from the oscillator 23 for a preset period, and count this. It is configured to deliver output for a period of time. Then, the output of the reference signal generator 21 and the EX-OR circuit 1
The output of 8 is introduced into the EX-OR circuit 24, and the output of the reference signal generator 22 and the output of the EX-OR circuit 18 are introduced into the EX-OR circuit 25. The output of the EX-OR circuit 24 is introduced to one input end of the NOR circuit 26, the output of the EX-OR circuit 25 is introduced to the other input end of the NOR circuit 26 via the NOT circuit 27, and the NOR circuit 26 is further introduced. Is introduced into the control end of the gate drive circuit 9 via the NOT circuit 28.

Next, the operation of the monitoring device configured as described above will be described with reference to FIG.

First, the superconducting coil 1 is kept in a normal superconducting state, the mechanical switch 6 is turned on in this state, and the thyristors 4a and 4b are controlled to ignite every half wave, so that the superconducting coil 1 receives an alternating current of 50 Hz. Is flowing. At this time, the reference signal generators 21 and 22 have a time limit of 5 ms.
Is set to.

As described above, when the superconducting coil 1 is in the normal state and the alternating current is flowing, the control end of the gate drive circuit 9 is always held at the logical value "0" as shown by the solid line in FIG. . That is, as shown in FIG.
There is exactly a phase difference of .pi. / 2 between the output E of I and the output I of the comparator 15, and the EX-OR circuit 18 outputs an output signal of exactly .pi. / 2 width, that is, 5 ms width. It The output of the reference signal generator 21 is sent for 5 ms from the rising edge of the signal E and 5 ms from the falling edge of the signal E, and the output of the reference signal generator 22 is for 5 ms from the rising edge of the signal I. It is transmitted for a period of 5 ms after the fall of I. Therefore, the EX-OR circuit 2
The output of 4 is always kept at "0", and the output of the EX-OR circuit 25 is always kept at "1". The output of the EX-OR circuit 25 is N
Since it is introduced into the NOR circuit 26 via the OT circuit 27, the control end of the gate drive circuit 9 is always kept at "0". Therefore, the alternating current is continuously supplied to the superconducting coil 1.

By the way, when the superconducting coil 1 is quenched for some reason while the alternating current is flowing through the superconducting coil 1 as described above, the resistor R is connected in series with the superconducting coil 1 as shown in FIG. It is equivalent to the state. When the impedance of the superconducting coil 1 is a combination of the inductance and the resistance, the phase difference between the voltage and the current across the superconducting coil 1 is necessarily π / 2 or less.
Now, if the phase of the current advances as shown by the broken line in FIG. 2 and the phase difference becomes π / 2 or less, the time width of the output of the EX-OR circuit 18 also becomes 5 ms as shown by the broken line in FIG. It becomes the following. The output of the reference signal generator 21 rising from the rising of the signal E is set to 5 ms as described above. Therefore, an output is sent from the EX-OR circuit 24, and eventually a signal "1" is given to the control end of the gate drive circuit 9 as shown by the broken line in FIG. In this way, when the signal "1" is given to the control end, the gate drive circuit 9 stops its operation. Therefore, thereafter, the thyristors 4a and 4b
Is not given a gate signal. Therefore, the current supply to the superconducting coil 1 is stopped, and the superconducting coil 1
Protection will be realized. The above description is an example in which the phase of the current has advanced and the phase difference between the voltage and the current has become π / 2 or less, but the phase of the voltage has been delayed and the phase difference between the voltage and the current has been π / 2. The same operation is performed in the following cases.

In spite of this extremely simple structure, it is possible to reliably detect the quench of the superconducting coil 1 and thereby contribute to the realization of appropriate treatment during the quench.
In this case, the superconducting coil 1 itself does not need to be specially processed, and since the signal processing is performed digitally, it is not affected by noise.
After all, the above-mentioned effects can be exhibited.

The present invention is not limited to the above embodiment. That is, in the above-mentioned embodiment, the voltage signal and the current signal are taken out through the isolation amplifier, but the isolation amplifier may be replaced with an isolation transformer or a capacitive coupler. Further, the semiconductor switch may be replaced with another switch as long as it does not cause a current-free disconnection phenomenon.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a monitoring device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the device, and FIG. 3 is an equivalent circuit diagram when a quench occurs in a superconducting coil. Is. DESCRIPTION OF SYMBOLS 1 ... Superconducting coil, 5 ... Semiconductor switch, 7 ... AC power supply, 8 ... Gate circuit, 9 ... Gate drive circuit, 12 ... Current detector, 14, 15 ... Comparator, 16, 18, 1
9, 24, 25 ... EX-OR circuits, 21, 22 ... Reference signal generator, 23 ... Oscillator.

Claims (2)

[Claims] 1. A voltage detecting means for detecting a voltage across a superconducting coil excited by an AC power source, a current detecting means for detecting a current flowing through the superconducting coil, and a voltage signal obtained by the voltage detecting means. 2. A superconducting coil monitoring device, comprising: a phase difference determining means for outputting a signal when the phase difference between the current signal obtained by the current detecting means and the current signal is .pi. / 2 or less. 2. The phase difference judging means means for producing a signal having a time width corresponding to the phase difference between the voltage signal obtained by the voltage detecting means and the current signal obtained by the current detecting means,
The superconducting coil monitoring device according to claim 1, further comprising a circuit for comparing the time width of the signal generated by this means with the signal of the reference time width.