JPS62176Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a quench detection device for a superconducting coil.

Superconducting coils have an accident called quench. This is a phenomenon in which a minute portion of a superconducting coil transitions from superconductivity to normal conductivity for some reason when electricity is applied, and Joule loss occurs in that portion, causing heat generation. If this heat generation is greater than the cooling capacity of the superconducting coil's coolant, such as liquid helium, the temperature of the normal conducting part will rise, resulting in the destruction of the superconducting properties, the expansion of the normal conducting part, and eventually the entire superconducting coil It becomes conductive, leading to destruction of the entire coil.

For this reason, a quench detection device is provided to detect the abnormal voltage that appears when normal conduction occurs, thereby tripping the power supply or disconnector. At this time,
The energy stored in the superconducting coil is consumed by the protective resistance circuit, suppressing the temperature rise of the superconducting coil.

FIG. 1 shows the general configuration of a detection circuit, in which DC current is supplied to a superconducting coil 5 through an excitation AC power source 1, a rectifier 2 (including a stabilizing circuit), and a DC disconnector 3.

When a quench accident occurs in superconducting coil 5,
The quench detector 6 detects this, and its output contact 6a excites the trip coil of the DC or disconnector 3 to trip the DC or disconnector 3, as shown in Figure 4, and the DC or disconnector 3 is tripped. The protective resistor 4 consumes the energy as Joule heat, reduces the current, and reduces the temperature rise of the superconducting coil 5.

The principle of the quench detection device will now be explained with reference to FIG. First, voltage signals at both ends of the superconducting coil 5 are input to the quench detector 6, and a bridge circuit is formed by the A section, the B section of the superconducting coil 5, and the potentiometer 7. An isolation amplifier 8 is also provided to isolate the voltage signal. The potentiometer 7 is adjusted in advance so that the signal input to the voltage comparator 9 is 0 when the superconducting coil 5 is normal.

When the superconducting coil 5 is normal, the pure resistance of parts A and B is zero, but if a quench accident occurs in a part of the superconducting coil 5, a pure resistance R is generated in that part. The bridge circuit becomes unbalanced due to R, and a differential voltage signal is input to the voltage comparator 9. Note that the magnitude of this pure resistance R varies depending on the degree of the quench accident and is not a constant value.

The voltage comparator 9 operates when the voltage signal exceeds a certain level, but if a quench accident is detected only by the voltage comparator 9, noise may be generated due to the fact that the superconducting coil 5 and the quench detector 6 are not electrically insulated. detection, making it difficult to distinguish between the two.

Therefore, timer 1 is connected in series with voltage comparator 9.
0 is connected, and when the voltage signal continues to be at a certain level or higher for a set time or longer, it is detected as a quench accident and the contact 6a is closed.

In the above conventional quench detection device, the third
The current sweep status shown in the figure (UP, HOLD, FLAT−
Although quench accidents are detected with the same sensitivity for both TOP and DOWN, this method can accurately detect quench accidents when the superconducting coil 5 is energized (UP) or demagnetized (DOWN). is difficult.

The reason for this is that while the superconducting coil 5 is being energized or demagnetized, the bridge circuit has an unbalanced voltage (R ₁ −
This is because the combined voltage of _R2 )i and the unbalanced voltage ( _L1 - _L2 )di/dt of the inductance due to current sweep is detected. Here, R ₁ and R ₂ are pure resistance components that appear due to the quench accident that occurred in parts A and B of the superconducting coil 5, respectively, and as mentioned above, their values are not constant but vary. .

That is, the detection voltage V ₁ of the quench detector 6 is expressed by the following formula.

V ₁ = (R ₁ - R ₂ ) i + (L ₁ - L ₂ ) di/dt...(1) The present invention is designed to reduce the induced current in the superconducting coil even when the superconducting coil is energized (UP) or demagnetized (DOWN). Provides a rational superconducting coil quench detection device that can reliably detect a quench accident by canceling the unbalanced voltage component (L ₁ −L ₂ ) di/dt and detecting only a pure resistance voltage drop. The purpose is to

An embodiment of the present invention is shown in FIG.

In Fig. 5, 11 is an amplifier used when the conducting current is small, 12 is a current comparator for detecting the level of the conducting current, and 13 is the current sweep speed (di/dt).
A detection circuit, 14 is a multiplication circuit that calculates the unbalanced voltage V ₂ = (L ₁ - L ₂ ) di/dt of the induced voltage of the superconducting coil 5, 15 is a current detector of the superconducting coil, and 16 is V ₁ -
This is an arithmetic circuit that calculates V ₂ , and the other parts are the same as in FIG. 2.

In Fig. 5, if a quench accident occurs in the superconducting coil 5 during excitation (UP) or demagnetization (DOWN), an unbalanced voltage (R ₁
−R ₂ )i can be determined in the arithmetic circuit 16 as a differential voltage V ₁ −V ₂ obtained by subtracting the unbalanced voltage V ₂ of the induced voltage of the superconducting coil 5 from the detection voltage V ₁ of the quench detector 6.

The unbalanced voltage component V ₂ of the induced voltage is detected by the detection circuit 13 as the current sweep speed (di/dt), and multiplied by the value (L ₁ −L ₂ ) read in advance in the multiplier circuit 14. Find out.

Next, the operation shown in FIG. 5 will be explained with reference to a typical current sweep pattern shown in FIG.

If the energizing current value during UP operation has not reached the set level Io, the current comparator 12 operates and the contact 12a is closed, and the pure resistance voltage drop (V ₁ - V ₂ ) of the superconducting coil 5 is applied to the amplifier 11. If the voltage is input and exceeds the set voltage via the voltage comparator 9 and timer 10 for a set time or longer, the contact 6a is closed and a contact signal is output.

Next, during UP operation, the energizing current value changes to the set level Io.
When the current comparator 12 becomes inactive, the contact 12b closes, and the compensated pure resistance voltage drop (V ₁ -V ₂ ) is directly input to the voltage comparator 9 and timer 10 without going through the amplifier 11. If this voltage is higher than the set voltage and continues for longer than the set time, the contact signal 6a is output.

During HOLD and FLAT-TOP, the current sweep speed (di/dt) is 0, and the energizing current value is higher than the set level _I0 , so the voltage comparator 12 is inactive, the contact 12b is closed, and the voltage A pure resistance voltage drop (V ₁ -V ₂ ) is input to the comparator 9 and the timer 10, and when this is higher than a set voltage and continues for a set time or longer, a contact signal 6a is output.

During DOWN operation, if the current flow value is equal to or higher than the set level _I0 , the current comparator 12 becomes inactive and the contact 12b closes, and the voltage comparator 9 and timer 10 have the pure resistance voltage drop (V) of the superconducting coil 5. ₁ -V ₂ ) is input, and when this voltage exceeds the set voltage of the comparator 9 and continues for longer than the set time of the timer 10, the contact signal 6a is output.

Next, during DOWN operation, the current value changes to the set level I ₀
In the following cases, the current comparator 12 operates, the contact 12a closes, and the pure resistance voltage drop (R ₁ - R ₂ )i of the superconducting coil 5 is input to the amplifier 11,
The amplified signal is sent to voltage comparator 9 and timer 1.
0, and when this voltage is higher than the set voltage and continues for longer than the set time, the contact signal 6a is output.

As explained above, according to the present invention, even when the superconducting coil is energized or demagnetized, the unbalanced voltage component of the induced voltage of the superconducting coil 5 is canceled and only the unbalanced voltage component of the pure resistance voltage drop is detected. Accidents can be detected accurately and reliably. Furthermore, if the pure resistance voltage drop is amplified when the conducting current is small, the detection accuracy can be increased and quench accidents can be detected, improving the stability of the entire system and extending the life of the superconducting coil. be able to.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the overall configuration of the detection circuit, Figure 2 is a circuit diagram of a conventional detector, Figure 3 is a diagram showing a typical current sweep pattern, and Figure 4 is a diagram showing DC and disconnection operations. FIG. 5 is a circuit diagram showing an embodiment of the present invention, and FIG. 6 is an explanatory diagram of the operation of the current comparator in the present invention. 5...Superconducting coil, 8...Isolation amplifier, 9...
...Voltage comparator, 10...Timer, 11...
amplifier, 12... current comparator, 13... current sweep speed detection circuit, 14... multiplication circuit, 15...
...Current detector, 16...Arithmetic circuit.

Claims (1)

[Scope of utility model claims] In a superconducting coil quench detection device that detects an unbalanced voltage of a resistance voltage drop in two parts of a superconducting coil, and detects that a quench accident has occurred in a superconducting coil when the magnitude of this detection signal is greater than a predetermined value, Using a current sweep speed detection circuit that detects the rate of change of the current in the superconducting coil, and the product of the difference in inductance of the two parts and the rate of change of the current, determine the unbalanced voltage V ₂ of the induced voltage in the two parts. The difference voltage (V ₁ - V ₂ ) between the terminal voltage drop difference voltage V ₁ of the above two parts and the above unbalanced voltage component V ₂ is derived as the unbalanced voltage component of the resistance voltage drop in the multiplier circuit. Features: A quench detection device for superconducting coils.