JPH08330128A - Quench detecting method for superconducting coil - Google Patents

Abstract

PURPOSE: To provide a method for detecting the quench of a superconducting coil with high reliability by reducing the detecting error and the calculating error of a quench voltage by excluding the influence of the coil and other component having electromagnetic synergistic action. CONSTITUTION: The primary side voltage V1, secondary side voltage V2 and primary side current I1 and secondary side current I2 of a transformer 14 formed of a primary winding 10 and a secondary winding 12 of superconducting coils are detected, and input to an A-D converter 26. A predetermined circuit calculation is conducted by a DSP 32 by using the detected values digitally converted by the converter 26, and the quench resistances when quench occurs at the windings 10, 12 are calculated. These resistances are compared with a threshold value Rr by a comparator 34, the time exceeding the value Rr is measured by a timer 36, and when the time exceeds the reference time Tr, a quench detection signal is outputted from the timer 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting coil, and more particularly to a method of detecting a quench of a superconducting coil which is used in a superconducting motor or a superconducting transformer and in which an induced electromotive voltage is generated by other components.

[0002]

2. Description of the Related Art Generally, in a superconducting coil, it is necessary to detect the occurrence of quench with high reliability for safety reasons.

In particular, there has been a long-felt demand for a quench detection method capable of performing quench detection even when quenches occur at two or more locations at the same time.
This publication discloses such a detection method.

FIG. 6 shows the configuration of the quench detecting device for a superconducting coil disclosed in the above-mentioned conventional example. In FIG. 6, the voltage across the superconducting coil 100 is input to one terminal of the voltage comparator 104 via the insulation 102. On the other hand, the current flowing through the superconducting coil 100 is the current detector 1
The output of the current detector 106 is input to the terminal voltage calculator 108. In the terminal voltage calculator 108, a value obtained by multiplying the time differential of the current by the inductance, that is, L · dI / dt corresponding to the voltage is output and input to the other terminal of the voltage comparator 104.

In the voltage comparator 104, the superconducting coil 10
The voltage between both ends of 0 is compared with the voltage equivalent calculated by the terminal voltage calculator 108 from the time change of the current flowing through the superconducting coil 100, and the output is input to the voltage comparator 110 of the next stage. In the voltage comparator 110, the voltage comparator 10 of the previous stage
The output of 4 is compared with the detection reference voltage Vr, and when it becomes larger than Vr, the timer 112 counts time.
When the state where the output of the voltage comparator 104 is larger than the detection reference voltage Vr becomes longer than the detection reference time Tr for quench detection, it is determined that the superconducting coil 100 has been quenched, and the timer 112 generates a quench detection signal.

In the above-described conventional example, the superconducting coil 100 is not divided into a plurality of parts for quench detection, but the voltage across the superconducting coil 100 is compared with the output of the terminal voltage calculator 108 to obtain Since quench detection is performed, it is possible to detect even if quench occurs simultaneously in a plurality of places.

[0007]

However, in the above conventional example, since the voltage across the superconducting coil 100 is calculated as the sum of the induced electromotive force due to the self-inductance L and the voltage due to the resistance, it is used for the superconducting motor. In this case, the reaction of the armature (rotor) may occur, and when it is used in a superconducting transformer, the influence of electromagnetic interaction such as induced electromotive force due to the secondary current may float, which may cause malfunction. For this reason,
Superconducting motor, superconducting transformer, bridge type SMES (superconducting magnetic energy storage device, Super Condu
ctingMagnetic Energy Stra
There is a problem that it is difficult to apply ge) to superconducting coils.

In the case of SMES, superconducting transformer, etc., the normally used voltage is at the level of several kV, and the voltage due to quenching therein is at the level of mV. Therefore, there is a problem that it is difficult to separate and detect the quench voltage with a general inexpensive measurement and detection system.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to eliminate the influence of other components having an electromagnetic interaction with the superconducting coil and to eliminate the detection error and the calculation error of the quench voltage. A small and highly reliable method of detecting a quench in a superconducting coil is provided.

[0010]

In order to achieve the above object, the present invention is used for a stator of a superconducting motor, a primary coil of a superconducting transformer, or the like, and a rotor of a superconducting motor or a secondary coil of a superconducting transformer. A method for detecting a quench of a superconducting coil having an electromagnetic interaction with other components such as a superconducting coil by monitoring the voltage across the superconducting coil and considering the electromagnetic interaction with the other components. It is characterized in that the induced electromotive voltage generated in the superconducting coil is calculated, and the monitored both-end voltage of the superconducting coil is compared with the calculated induced electromotive voltage to determine whether or not the quench occurs in the superconducting coil.

A quench detecting method for a superconducting coil used in a superconducting transformer, wherein the primary side voltage, the primary side current, the secondary side voltage and the secondary side current of the superconducting transformer are respectively detected, The electric resistance generated in the superconducting coil is calculated from the circuit equation using these values, the calculated electric resistance and the reference resistance are compared, and the calculated electric resistance exceeds the reference resistance. It is characterized in that whether or not the quenching of the superconducting coil has occurred is determined by whether or not has continued for a predetermined time.

The method for detecting quenching of the superconducting coil is characterized in that the presence or absence of quenching of the superconducting coil is judged when the rate of change of the current flowing through the superconducting coil is small.

[0013]

According to the above construction, since the induced electromotive voltage generated in the superconducting coil is calculated by the equation considering the influence of the other components having electromagnetic interaction with the superconducting coil, these influences are eliminated. be able to.

Further, since the presence or absence of the quench is judged when the rate of change of the current is small, it is possible to reduce the detection error and the calculation error of the quench voltage.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

Example 1. FIG. 1 shows an example in which the quench detection method for a superconducting coil according to the present invention is applied to a transformer. In FIG. 1, a transformer 14 composed of a primary winding 10 and a secondary winding 12 has a power source 16 on its primary side.
However, the load 18 is connected to the secondary side. Transformer 1
The voltage V1 on the primary side of No. 4 via the insulation 20 and the voltage V2 on the secondary side via the insulation 22 respectively.
After the noise is removed by 4, the signal is input to the A / D converter 26. The primary side current I1 of the transformer 14 is the ammeter 2
8 and the filter 24, and the secondary current I2 is input to the A / D converter 26 via the ammeter 30 and the filter 24, respectively.

A predetermined operation is performed by the digital signal processor (DSP) 32 on each of the voltages and currents on the primary side and the secondary side which are digitally converted by the A / D converter 26. The contents of this calculation will be described below.

FIG. 2A shows the transformer 14 shown in FIG.
FIG. 2B shows an equivalent circuit of the transformer shown in FIG. 2A. The transformer 14 uses superconducting coils on both the primary and secondary sides, and the following description will be given assuming that the winding ratio is 1: 1.

In FIG. 2B, the wiring resistance R on the primary side
1. Quench resistance when quench occurs in the primary winding 10 which is a superconducting coil, Rq1, primary side leakage reactance is L1, and secondary side wiring resistance is R2, superconducting coil secondary winding When the line 12 is quenched, the quench resistance is Rq2, the secondary side leak reactance is L2, the mutual reactance of the transformer 14 is M, and the primary side power supply voltage is V1 and the secondary side load is When the generated voltage is V2, V1 and V2 are expressed by the following equations.

[0020]

V1 = I1 (R1 + Rq1) + (M + L1) (dI1 / dt) -M (dI2 / dt) (1)

## EQU00002 ## V2 = I2 (-R2-Rq2)-(M + L2) (dI2 / dt) + M (dI1 / dt) (2) The above equations (1) and (2) are the primary of the transformer 14. It is an equation considering the electromagnetic interaction on the secondary side.

Here, M, L1, L2, R1 and R2 are known. If the primary winding 10 and the secondary winding 12 are not quenched, Rq1 and Rq2 are 0, so that the DSP 32 shown in FIG. 1 causes the rate of change of I1 and I2 with time, that is, dI1 / dt and dI2 / dt is calculated, and I1 detected by these and ammeters 28 and 30
I2 and V1 and V from equation (1) and equation (2)
2 can be calculated.

As described above, V1 and V2 calculated by the DSP 32 are the primary side voltage V1 measured on the primary side and the secondary side of the transformer 14 by the comparator 34 of FIG.
And the secondary side voltage V2, respectively. Comparator 34
Is set to a threshold value Vr that serves as a reference for this comparison.

When the primary winding 10 or the secondary winding 12 is quenched, a difference occurs between the calculated V1 and V2 and the actually measured V1 and V2. When the threshold value Vr is exceeded, the timer 36 is started. Then, when the duration of the state where the above voltage difference exceeds the threshold value Vr exceeds the reference time Tr, it is determined that a quench has occurred, and the timer 36 outputs a quench detection signal.

Next, another quench detection method using the circuit of FIG. 1 will be described.

When the above equations (1) and (2) are modified, Rq1 and Rq2 are expressed as follows.

[0026]

## EQU00003 ## Rq1 = (V1- (M + L1) (dI1 / dt) + M (dI2 / dt)) / I1-R1 (3)

## EQU00004 ## Rq2 =-(V2 + (M + L2) (dI2 / dt) -M (dI1 / dt)) / I2-R2 (4) As mentioned above, M, L1, L2, R1 and R2 are known. Therefore, if I1, I2, V1 and V2 are detected, Rq1 and Rq2 can be calculated by the DSP 32 shown in FIG. 1 using the equations (3) and (4).

The above-mentioned Rq1, R calculated by the DSP 32
q2 is input to the comparator 34, where it is compared with a predetermined threshold value Rr set in the comparator 34. If the primary winding 10 and the secondary winding 12 are not quenched, Rq1 and Rq2 should be smaller than this threshold value Rr. Therefore, when these values exceed Rr, the timer 36 is activated, and when the duration of this state exceeds the reference time Tr, the timer 36 outputs a quench detection signal.

In the above-mentioned transformer 14, the electromagnetic interaction between the primary side and the secondary side is the rate of change of current, that is, dI.
It increases when 1 / dt and dI2 / dt are large. Therefore, in order to improve the accuracy of quench detection, it is preferable to perform quench detection in a section where I1 and I2 are large and the rate of change with time is small.

For example, in the case where the quench detection of the primary winding 10 is performed, when the waveform of V1 is Vm · cosωt, the quench determination may be made in a period such that | cosωt |> α. In this case, α is a predetermined value smaller than 1.

If the average power factor φ is taken into consideration, φ =
As cos θ, the quench determination may be made in a period where | cos (ωt + θ) |> α.

Further, when the period for making the quench judgment is determined by the primary side current I1, the waveform of I1 is set to Imc.
When osωt is set, the period may be set as | cosωt |> α.

In this embodiment, the case where the quench detection method for a superconducting coil according to the present invention is applied to the transformer 14 has been described, but it can also be applied to a superconducting motor. In this case, the circuits on the secondary side shown in FIGS. 1 and 2 correspond to the rotor of the motor. Therefore, the physical quantities on the secondary side in equations (1) to (4) are the currents of the rotor of the motor and The equation can be established by substituting the rotation angle.

Example 2. FIG. 3 shows an example in which the quench detection method for a superconducting coil according to the present invention is applied to a circuit using a semiconductor switching element. In FIG. 3, the circuit on the secondary side is omitted, and the insulation 20,
Filter 24, A / D converter 26, primary side ammeter 2
8, the DSP 32, the comparator 34, and the timer 36 are the same as those shown in FIG.

In FIG. 3, a persistent current switch 42 is connected to the superconducting coil 40, and further connected to a bridge 44. The bridge 44 supplies a current to the load 46 from the superconducting coil 40 in addition to the current from the power supply 16 according to the power consumption of the load 46.
It has a function of switching between a mode in which the current from the power source 16 which cannot be consumed by the load 46 is stored in the superconducting coil. The bridge 44 includes four transistors S1 and S (-) each having a diode connected between the collector and the emitter.
1, S2, and S (-) 2. Note that S
(−) Means inversion, and when H is input to the transistor S1 as a control signal, the transistor S (−)
1 means that L is input as a control signal.

FIG. 4 shows a block diagram of the control circuit of the bridge 44. Control signal C output from this control circuit
S1 is a control signal for the transistors S1 and S (-) 1, and control signal CS2 is a control signal for the transistors S2 and S (-) 2.

The quench detection READY signal and the PWM signal are input to the control circuit shown in FIG. The quench detection READY signal is sent to the OR circuit 48 via the buffer 54 and to the AND circuit 50 by the inverter 5
It is input via 2.

Normally, the quench detection READY signal is in the L state, and the PWM signal repeats the H and L states according to the power consumption of the load 46. When the PWM signal is H, the output CS1 of the OR circuit 48 is H. The control signal CS2 output from the AND circuit 50 is A
Since the signal obtained by inverting the quench READY signal (L) by the inverter 52 is input to the ND circuit 50,
This is also H.

On the other hand, when the PWM signal is L, the control signal CS1 output from the OR circuit 48 is L, and the control signal CS2 output from the AND circuit 50 is also L.

As described above, this PWM signal is applied to the load 46.
The pulse widths of H and L are determined according to the power consumption of the control signals CS and C depending on H and L of the PWM signal.
Since H and L of S2 are determined, quench detection REA
When the DY signal is at L, this causes the bridge 44 to
ON / OFF of two transistors will be switched.

That is, when the PWM signal is H and the control signals CS1 and CS2 are H, the transistors S1 and S2 of the bridge 44 are turned on and the transistor S is turned on.
(-) 1 and S (-) 2 are turned off. On the contrary, P
When the WM signal is L, the transistors S1 and S2 of the bridge 44 are turned off, and the transistor S (−) 1
And S (-) 2 are turned on.

By the operation of the bridge 44, the mode in which the current is supplied from the superconducting coil 40 to the load 46 and the mode in which the surplus current from the power source 16 is stored in the superconducting coil 40 are switched. When the two modes are switched, the polarity of the voltage applied to the superconducting coil 40 is inverted, so that the superconducting coil 4 can be switched in accordance with H and L of the PWM signal.
The voltage between both ends of 0 repeats the state of the power supply voltage V and the state of -V. For example, the power supply voltage V is 300V
In the case where is adopted, the inversion operation is repeated between 300V and −300V. This state is shown in FIG.

When the quench of the superconducting coil is detected in the state shown in FIG.
Since the quench detection must be performed in the state where the voltage related to 0 is 300 V or −300 V, and the quench voltage is several mV, the accuracy of the quench detection cannot be improved as it is.

Therefore, in this embodiment, the quench detection period of the superconducting coil 40 is set by setting the quench detection READY signal input to the control circuit shown in FIG. 4 to H. When the quench detection READY signal is input as H, the OR circuit 48 includes the buffer 54
Since H of the quench READY signal is input via the, the control signal CS1 which is the output of the OR circuit 48 also becomes H. Further, since the quench detection READY signal is inverted and input to the AND circuit 50 via the inverter 52, the control signal CS2 output from the AND circuit 50 becomes L. As a result, the transistors S1 and S (-) 2 of the bridge 44 are turned on and S2 and S (-) 1 are turned off.

The current flowing through the superconducting coil 40 flows through the loop circuit via the transistor S1 and the diode connected between the collector and emitter of the transistor S (-) 2. Therefore, in this case, the bridge circuit 44
Only the voltage drop when passing through will occur.
This voltage effect is about 3V. This is shown in Figure 5.
It is shown in (b).

In FIG. 5A, the control signal C
Although the H and L states of S1 and CS2 are the same,
In the control signals CS1 and CS2 shown in (b), there is a section in which the timings of H and L are deviated. This section is a section in which the voltage applied to the superconducting coil 40 described above is 3V, and quench detection of the superconducting coil may be performed in this 3V section. By doing so, the quench can be detected in a state in which the voltage applied to the superconducting coil is low, so that the accuracy of the quench detection can be improved.

[0046]

As described above, according to the present invention,
Quench detection is performed using an equation that considers the electromagnetic interaction between the primary side and the secondary side, and the time when the quench detection is performed is limited to the time when the interaction between the primary side and the secondary side is small. Therefore, it is possible to provide a highly reliable quench detection method for a superconducting coil that can reduce detection errors and calculation errors.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment showing an example of a transformer using a quench detection method for a superconducting coil according to the present invention.

FIG. 2 is a circuit diagram around the transformer shown in FIG. 1 and its equivalent circuit diagram.

FIG. 3 is a circuit diagram of a second embodiment in which the quench detection method for a superconducting coil according to the present invention is applied to a circuit using a semiconductor switching element.

4 is a diagram showing a control circuit for generating a control signal for a bridge of the circuit shown in FIG.

5 is an explanatory diagram of the relationship between the control signal shown in FIG. 4 and the voltage applied to the superconducting coil.

FIG. 6 is a circuit diagram for explaining a conventional quench detection method for a superconducting coil.

[Explanation of symbols]

10 primary winding, 12 secondary winding, 14 transformer, 16
Power supply, 18, 46 load, 20, 22 insulation, 24 filter, 26 A / D converter, 28, 30 ammeter, 32
DSP, 34 comparator, 36 timer, 40 superconducting coil, 42 permanent current switch, 44 bridge, 4
8 OR circuit, 50 AND circuit, 52 inverter,
54 buffers.

Claims (3)

[Claims] 1. A superconducting coil which is used for a stator of a superconducting motor or a primary coil of a superconducting transformer and which has electromagnetic interaction with other components such as a rotor of a superconducting motor or a secondary coil of a superconducting transformer. A quench detection method, which monitors a voltage across a superconducting coil, calculates an induced electromotive voltage generated in the superconducting coil from an equation in consideration of electromagnetic interaction with the other constituent elements, and monitors the superconducting coil. A method for detecting quenching of a superconducting coil, characterized by comparing the voltage across both ends of the superconducting coil with the calculated induced electromotive force to determine whether or not quenching of the superconducting coil has occurred. 2. A quench detection method for a superconducting coil used in a superconducting transformer, comprising: a primary side voltage, a primary side current, a secondary side voltage of the superconducting transformer,
The secondary side currents are respectively detected, and by using these values, the electric resistance generated in the superconducting coil is calculated from the circuit equation, the calculated electric resistance and the reference resistance are compared, and the calculated electric resistance is calculated. A method for detecting quenching of a superconducting coil, comprising determining whether or not quenching of the superconducting coil has occurred depending on whether a state in which the electric resistance exceeds the reference resistance continues for a predetermined time. 3. The quench detection method for a superconducting coil according to claim 1 or 2, wherein the determination as to whether or not the quench occurs in the superconducting coil is performed when the rate of change of the current flowing through the superconducting coil is small. A method for detecting a quench in a superconducting coil.