JPH02202004A - Superconducting coil device - Google Patents

Abstract

PURPOSE:To make it possible to protect a coil by detecting a quenching generated on the coil in a highly sensitive manner by a method wherein, when a DC chopper circuit is turned OFF, a protective means, with which the excitation of the coil of a superconducting material will be stopped, is provided based on the detected voltage of the coil. CONSTITUTION:When a DC chopper circuit is turned OFF by receiving a synchronizing signal from a DC chopper circuit 12, a voltage detection means 13 detects the bridge voltage of a bridge circuit 6. A protective means is composed of a tripping signal circuit 14b, which works when the detected voltage of the voltage detection means 13, in other words, when the count of a counter 14a which counts the number of times sampling voltage exceeded the prescribed value, exceeded the prescribed value, and an open-circuit signal is sent to a circuit breaker 2. As the voltage of a coil is detected when the DC chopper circuit is turned OFF as above-mentioned, the effect of the value of the voltage while the coil is being excited is not inflicted upon the detected value, a quenching can be detected in a highly sensitive manner without being affected by the magnitude of the excitation voltage, and the coil can be protected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting coil device equipped with a novel protection device.

[Conventional technology]

FIG. 5 is a circuit diagram showing an example of a conventional superconducting coil device shown in the literature "Applied Superconductivity" (published by Nikkan Kogyo Shimbun) edited by Hiroyasu Ogiwara. FIG. 6 is an explanatory diagram showing temporal changes in voltage, current, etc. when quench occurs in the coil.
(aJ diagram is the coil voltage, (b) diagram is the same current, (c)
The figure shows temporal changes in the output voltage (bridge voltage) of a bridge circuit (described later) that detects quench. In Figure 5, (1) is a DC power supply, (2) is a DC power supply (
1) is a circuit breaker installed on the load side, (2a) is a circuit breaker (
The tripping coil (2) and (3) are superconductor coils that are excited by the DC power supply (1) via the circuit breaker (2), and the first and second coils (3a) have approximately the same inductance. ), (3b) are connected in series, and the first and second coils (3a>, (3b)
One output terminal (4a) is provided at the connection point. (
5a) and (5b) are impedance elements, in this example they are resistors with the same value, and as shown in the figure, each is connected in series and the other output terminal (4b) is provided at the midpoint of the coil. (3) is connected in parallel with the coil (3a)
, (3b) and resistors (5a), (5b) form a bridge circuit (
6). This bridge circuit (6) is designed so that the coils (3a) and (3b) have approximately equal inductance, so the coils (3a) and (3b
) is canceled out and the effect of the inductance of the output terminal (4
a) and (4b) (hereinafter referred to as bridge voltage), but when a quench occurs in the coil (3a) or (3b), the voltage at the quench portion appears as a bridge voltage. (7) is a voltage detection device, which is composed of an amplifier (7a) and a voltage relay (7b), and when the bridge voltage of the bridge circuit (6) exceeds a predetermined value, it issues a signal and disconnects the coil. (2a) opens the circuit breaker (2). (81 is connected in parallel to coil (3), and when quench occurs in coil (3), coil (
It is a protective resistor that consumes the energy of 3) as Joule heat.

In the superconducting coil device configured as described above, the operation when, for example, a quench occurs in the portion (A) of the coil (3a) will be described with reference to FIG. Circuit breaker (
2) is opened and the coil (3) is excited by the DC power supply (1) at a constant voltage Em (Fig. 6(a)).

If the inductance of coil (B) is L [H], the coil current increases at a constant rate according to the formula E = L''/d-.For example, if the inductance of coil (3) is 16.7 (V ) Apply DC voltage to Sult 10
00(A/min) (16,7(A/s))
The current increases as shown in Figure (b). The bridge voltage at this time is shown in FIG. 6(c), and each impedance element making up the bridge circuit, that is, the coil
), (3b), and it is difficult to perfectly balance the values of resistors (5a) and (5b), resulting in an imbalance in the bridge circuit, and during the excitation of coil β), a small residual voltage (ΔVO) due to this imbalance occurs. (+aV]).Here, when a quench starts to occur in the part (A) of the coil (3a) at time TI, resistance is generated in that part and a bridge voltage as shown in the figure is generated. At time T2, the bridge voltage exceeds a predetermined value ΔVl [mV], and the state in which this ΔVl (mV) is exceeded continues for a predetermined time ΔT (
s) Next, at time T3, the voltage detection device (■) operates and issues a signal to open the circuit breaker (21) and close the coil (3).
) stops excitation. When the circuit breaker (2) is opened, the current in the coil (3) decreases rapidly as shown in Figure 6(b), so the voltage in the coil (3) decreases rapidly as shown in Figure 6(a). , and the polarity is reversed. This voltage is applied to the protective resistor (8), the energy stored in the coil (3) is consumed as Joule heat, and the voltage of the coil (3) decreases and finally becomes zero.

In addition, in the above conventional example, the coils (3a), (3b
) The bridge circuit (6) is used to detect the quench of the coil (3a) and (3b) by sensitively detecting the minute voltage generated at the quench section of the coil (3a) and (3b).
) to release the energy to the outside, and this is especially necessary in a highly stable coil since the voltage generated during quenching is small. Although not shown, there is a certain amount of impedance on the power supply side, and when a quench occurs, the voltage of the coil changes, so this change is detected and protected without using the bridge circuit (6) as described above. It is also possible. Since the excitation voltage of the coil is always superimposed, the detection sensitivity is low, but it is used when a large voltage is generated immediately after quenching, such as in a closely wound coil.

[Problem to be solved by the invention]

Since the conventional superconducting coil device is configured as described above, the coil is excited by a pulse excitation method using a DC chopper circuit using a switching element such as a thyristor instead of the DC power supply (1) in Fig. 5. In this case, there is a residual voltage in the bridge circuit (6) due to the unbalance as described above, so even if the coil is normal, this residual voltage periodically appears as a large bridge voltage.
It is difficult to detect the occurrence of coil quenching with high sensitivity. This will be explained in detail with reference to FIG. 7, which is an explanatory diagram showing changes in coil voltage, current, and bridge voltage in this case. A pulsed voltage El (V) is periodically applied to the coil (3) as shown in figure (a), and a voltage El (V) is applied to the current of the coil (3) as shown in figure (b). On the other hand, the bridge voltage increases as shown in Fig. 7 (c
), the residual voltage ΔV3 (mV) when the pulsed voltage El (Vl is applied) is generated periodically.The on-time ratio of the DC chopper circuit in this case is set to 10%.
Then, the pulsed voltage corresponding to the case of continuous excitation in the conventional example shown in Fig. 6 becomes 10 times, and the residual voltage ΔV3 (
mV] is 10 times the conventional residual voltage ΔVO (mV). Therefore, this residual voltage ΔV3 (mV)
The operating setting value of the voltage detection device (7) must be biased to a high value by this amount to prevent the coil (3a) from operating as shown in FIG.
When a quench occurs in A), a bridge voltage as shown in Fig. 7(d) is generated (the time axis in Fig. 7 is enlarged from Fig. 6), but the setting value of the voltage detection device ■ is Because of the above-mentioned reason, the remaining voltage ΔV3 (-1) is biased, so there is a problem that the quench detection sensitivity is low even though the bridge circuit (6) is used.

Furthermore, in the case of detecting coil quench by detecting changes in coil voltage without using a bridge circuit, since the above-mentioned pulsed voltage El (Vl is directly superimposed instead of as a residual voltage of the bridge circuit), This method could not be adopted because the detection sensitivity would decrease and effective protection could not be achieved.This invention was made to solve the above problems. The purpose of the present invention is to obtain a superconducting coil device equipped with a protection device that can detect and protect the quench of the coil with good sensitivity and reliability without being affected by the voltage.Also, even if a bridge circuit is used to detect the voltage at the quench part, the bridge circuit An object of the present invention is to obtain a superconducting coil device having a highly sensitive protection device in which detection sensitivity is not reduced due to unbalance.

[Means to solve the problem]

The superconducting coil device according to the present invention includes a voltage detection means for exciting a superconductor coil by a DC chopper circuit, and detecting the voltage of the coil when the DC chopper circuit is open in synchronization with the opening and closing of the DC chopper circuit; A protection means is provided which operates based on the voltage detected by the voltage detection means to stop excitation of the superconductor coil.

Further, a bridge circuit including the coil as an impedance element and outputting the quench of the coil as a voltage is used, and when the DC chopper circuit is open in synchronization with the opening and closing of the DC chopper circuit, the bridge circuit The present invention is provided with a voltage detection means for detecting voltage and a protection means that operates based on the detected voltage of the voltage detection means to stop excitation of the superconductor coil.

[For production]

Since the voltage detecting means in this invention detects the voltage of the coil when the DC chopper circuit is open, the effect of the voltage value during the excitation of the coil does not appear on the detected value, and it depends on the magnitude of the excitation voltage. The detection of quench with good sensitivity is the turning part. Further, since the unbalance of the bridge circuit used to detect the voltage of the quench section does not appear in the detected value of the voltage detection means, it is possible to detect the quench with high sensitivity using the bridge circuit.

[Embodiments of the invention]

FIG. 1 is a block diagram showing one embodiment of the present invention,
In the figure, (2) to (8) are the same as those of the conventional device shown in FIG. 5, so their explanation will be omitted. (11) is a DC power supply that supplies a constant voltage; (12) is a DC chopper circuit that is connected to this DC power supply (11) and opens and closes the circuit at a predetermined period;
13) is a voltage detection means that receives a synchronizing signal from the DC chopper circuit (12) and detects the bridge voltage of the bridge circuit (6) when the DC chopper circuit is open. In this example, the bridge voltage is detected only when the gate is open. It is composed of a sampling circuit (13a) for extracting data and an amplifier (13b). (+4) is a protection means that operates based on the voltage detected by the voltage detection means (13) to open the circuit breaker (2) and stop the excitation of the coil (3).
3) A counter (14a) that counts the number of times the detected voltage, that is, the sampling voltage exceeds a predetermined value, and when the counted value of this counter (14a) exceeds a predetermined value, it operates and issues an open signal to the circuit breaker (2). Tripping signal circuit (14b
).

Next, the operation will be explained. Figure 2 shows the coil (3a)
Voltage when quench occurs in part (A).

FIG. 3 is an explanatory diagram showing changes in current and the like. (a) As shown in the figure, the coil (3) is periodically excited by a pulsed voltage El by opening and closing a DC chopper circuit.

The current in the coil (3) increases as shown in Figure (b) every time the pulsed voltage E1 is applied. When voltage E1 is not applied, the gate of the sampling circuit (13a) is opened to take out the bridge voltage, amplified by the amplifier (13b), and output as a sampling voltage to the counter (14a). Therefore, time TI
When a quench occurs in part (A) of coil (3a) and the voltage at the quench part increases with time, the sampling voltage changes as shown in figure (c), and each time it exceeds the set voltage ΔVl, ( d) A counter (14a) counts as shown.

When the count value of this counter (14a) exceeds a predetermined value, the tripping signal circuit (14b) operates and issues a release signal to circuit breaker (2) to open circuit breaker (2) and remove coil (3).
Stops excitation. At this time, the energy stored in the coil (3) is transferred to the protective resistor (8) as in the conventional example shown in FIG.
consumed by Note that the reason why the trip signal circuit (14b) operates after the counter (14a) has counted a predetermined value is because the counter (14a) is activated due to noise.
If a) incorrectly counts, the circuit breaker (2) will be activated immediately by mistake.
This is to prevent the .

FIG. 3 is a block diagram showing another embodiment of the present invention, in which the voltage of the coil (3) is directly detected without using a bridge circuit to detect the voltage of the quench section. ) is the coil G) when the DC chopper circuit (12) is open upon receiving a synchronization signal from the DC chopper (12).
It is a voltage detection means for detecting the voltage of the coil (3), and is composed of a sampling circuit (23a) that extracts the voltage of the coil (3) when the gate is opened, and an amplifier (23b).
(24) is a protection means that operates based on the voltage detected by the voltage detection means (23) to open the circuit breaker (2) and stop the excitation of the coil (3). It is composed of a relay (24b). .

Next, the operation of this embodiment will be explained. Figure 4 is an explanatory diagram showing changes in voltage, current, etc. when quench occurs in the coil, and the voltage and current applied to coil (3) are the same as in Figures 2 (a) and (b). be. The sampling circuit (23a) causes the DC chopper circuit (12
) is open, the gate is opened to take out the voltage of the coil B), amplified by the amplifier (23b), and output as a sampling voltage. This sampling voltage is, for example, at time T
When quenching occurs in part (A) of coil (3a) at I and increases with time, it changes as shown in (c). This sampling voltage is converted into an integrator circuit (24
a) is integrated and output, and when it reaches a predetermined value ΔV4 (Vl), the voltage relay (24b) operates and shuts off PI (2
Release 1.

In the embodiment shown in FIG. 1, the coil (3) is composed of two coils (3a) and (3b), and a set of bridge circuits (6), voltage detection means (13), and protection means (
14), the same effect can be obtained even if the coil (3) is divided into more coils and a plurality of sets of bridge circuits, voltage detection means, and protection means are provided for protection.

Also, in the embodiment shown in FIG. 3, for example, the coil t3)
A voltage detection means (23) and a protection means (24) may be provided for each of the coils (3a) and (3b) constituting the circuit breaker (21). The excitation may be stopped on the DC power supply (11) side without opening.

In this case, the circuit breaker (2) can also be omitted.

In addition, although the DC chopper circuit (12) receives and samples the synchronizing signal for the voltage detection means (13) and (23), the coil (3) or the coil (3a constituting the same) , (3b) etc., sampling may be performed by detecting the voltage and determining the presence or absence of the excitation voltage, or the width of the sampling time may be set arbitrarily.
Note that the method for adjusting the opening/closing time ratio of the DC chopper circuit may be either pulse width modulation or pulse frequency modulation, and the present invention can be applied even to opening/closing that has no temporal regularity. The structure of the means may be arbitrarily selected as long as the object of the invention is not impaired.

〔Effect of the invention〕

As described above, according to the present invention, a superconductor coil is excited by a DC chopper circuit, and the voltage of the coil is detected when the DC chopper circuit is open in synchronization with the opening and closing of this DC chopper circuit. Therefore, it is possible to detect quench with high sensitivity without being affected by the magnitude of the excitation voltage, and reliable protection can be achieved at an early stage.

Therefore, the quench can be detected with sufficiently high sensitivity without using a bridge circuit to detect the voltage at the quench section of the coil, and in this case, there is no need to provide an output terminal to configure the bridge circuit in the middle of the coil. There is also no risk of burning out the coil due to abnormal voltage occurring at this output terminal when quenching occurs.

In addition, when a bridge circuit is used to detect the voltage in the quench section, it is not necessary to increase the operating value of the protection means to deal with the unbalance of the values of the impedance elements that make up the bridge circuit, and the sensitivity is improved. Quench detection becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 shows the voltage when quench occurs in the coil. FIG. 3 is a block diagram showing another embodiment of the present invention. FIG. 4 is an explanatory diagram showing changes in voltage, current, etc. when quench occurs. FIG. 5 is an explanatory diagram showing changes in current, etc. A circuit diagram showing an example of a conventional superconducting coil device, FIG. 6 is an explanatory diagram showing changes in voltage, current, etc. when quench occurs,
FIG. 7 is an explanatory diagram showing changes in voltage, current, etc. when a superconductor coil is excited by a DC chopper circuit. In the figure, (3) is a superconductor coil, (3a)
, (3b) are the first and second coils, (6) is the bridge circuit, (12) is the DC chopper circuit, (+31.
23) is a voltage detection means (!) is a defective means. In each figure, the same reference numerals indicate the same or corresponding parts. Agent: Patent Attorney Masuo Oiwa Figure 2a 2a Figure 3 Figure 5 Figure 6 Figure 4 Figure 7

Claims (2)

[Claims] 1. A DC chopper circuit, a superconductor coil connected to and excited by the DC chopper circuit, voltage detection means for detecting the voltage of the coil when the DC chopper circuit is open in synchronization with the opening and closing of the DC chopper circuit, and the A superconducting coil device comprising a protection means that operates based on the voltage detected by the voltage detection means and stops the excitation. 2. A DC chopper circuit, a superconductor coil connected to the DC chopper circuit and excited, a bridge circuit including the coil as an impedance element and outputting the quench of the coil as a voltage, and opening/closing of the DC chopper circuit. A superconducting coil device comprising voltage detection means for synchronously detecting the voltage of the bridge circuit when the DC chopper circuit is open, and protection means for operating based on the detected voltage of the voltage detection means to stop the excitation.