JPS6130511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the excitation, maintenance and control, and termination of the plasma current in a tokamak fusion device by means of an air-core current transformer coil located close to the vacuum vessel. The present invention relates to a power supply circuit for generating a state.

Generally, the current waveform of an air-core current transformer coil for excitation, control maintenance, and stopping of plasma requires an operation mode as shown in FIG. 1.
In FIG. 1a the current transformer coil current is shown and in FIG. 1b the corresponding plasma current. In the figure, T ₀ is the current transformer coil excitation time, T ₁ is the plasma current excitation time, T ₂ is the plasma control maintenance time, and T ₃
is the plasma stop time.

As is clear from the figure, the polarity of the current transformer coil current must be reversed between the current transformer coil excitation period T ₀ and the plasma control maintenance period T ₂ .
That is, it is necessary to switch the polarity of the DC power supply for the current transformer coil.

For the current transformer power supply circuit to handle this mode of operation, methods include (1) preparing a power source with a polarity opposite to that of the DC power source for the current transformer coil, and (2) using a mechanical polarity switch. is considered.

Figure 2a shows a conventional current transformer power supply circuit based on this polarity switching method using a reverse direction power supply.
FIG. b shows a conventional current transformer power supply circuit based on a polarity switching method using a mechanical switch.

In Figures 2a and b, LF is an air core current transformer coil, R is a variable resistor for time constant adjustment, PS ₁ F is a forward DC power supply for the current transformer coil, and PS ₁ R is a reverse DC power supply for the current transformer coil. It is a directional DC power supply. LS ₁ and
LS ₂ is an energy storage coil for plasma current excitation, and PS ₂ and PS ₃ are DC power supplies for energy storage. S ₁ , S ₂ , S ₃ are cut-off switches, S ₄ and S ₅ are switches for preventing backflow of energy storage coil current, SO, SO ₁ , SO ₂ , SO ₃ , SO ₄
is the on switch for reconnecting the power supply.

FIG. 2b shows only the different parts from FIG. 2a, and the illustration of the same parts as FIG. 2a is omitted.

In these conventional circuits, each coil is excited with DC current during plasma excitation, and the DC current is turned off in the order of S ₁ , S ₂ , and S ₃ at certain time intervals. The current in the air-core current transformer coil LF is made to flow through the variable resistor R, and the current in the energy storage coils LS ₁ and LS ₂ is made to flow through the air-core current transformer coil LF and the variable resistor R, so that the current is transformed. This generates a high voltage in the current transformer coil LF to ignite and excite the plasma circuit that is electromagnetically coupled to the current transformer coil LF. In the subsequent plasma control maintenance period _T2 , the polarity of the DC power supply device for the current transformer coil is switched.

By the way, both the polarity switching method using a reverse power supply shown in Figure 2a and the polarity switching method using a mechanical switch shown in Figure 2b have problems such as extremely short polarity switching time or economical problems, and poor performance. Balancing economic efficiency has become a major issue.
On the other hand, it may be more economical to excite the plasma by changing the current values of the current transformer coil LF and the energy storage coils LS ₁ and LS ₂ .
It is more economical to provide independent power supplies for each of them from the perspective of the entire system.

The purpose of the present invention is to take the above points into consideration,
An object of the present invention is to provide a current transformer power supply circuit that has good control performance and is economical.

The present invention uses an air-core current transformer coil in a tokamak-type nuclear fusion device to supply direct current to the air-core current transformer coil and energy storage coil in a current transformer power supply circuit for the purpose of plasma ignition, excitation, and maintenance of control. It is equipped with a plurality of DC power supply devices and a high voltage generation circuit for the purpose of igniting and exciting the plasma, and one of the DC power supply devices is connected to an air-core current transformer coil in order to easily maintain control of the plasma. It is characterized in that it is arranged so as to be able to connect with the DC power supply device of reverse polarity and is further provided with an input device, and plasma control is maintained by cooperation between the input device and the reverse polarity DC power supply device. It is something to do.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention.
Elements similar to those in FIG. 2 are designated by the same reference numerals.

PS ₁ is a DC power supply device for current transformer coils,
PS ₂ and PS ₃ are DC power supplies for energy storage coils. The DC power supply device PS ₂ is connected to the other DC power supply devices PS ₁ and PS ₃ so as to have opposite polarity.

A closing device MS ₀ is provided in the line L ₁ connecting the DC power supply device PS ₂ and the air-core current transformer coil LF. Also,
Energy storage coil LS ₁ for plasma current excitation
is connected between the line _L1 and the line _L2 that connects the shrink cutoff switch _S2 and the backflow prevention switch _S4 .

Next, the operation of the embodiment circuit shown in FIG.
The explanation will be given according to the operation sequence shown in the figure.

(i) Current transformer coil excitation time (T ₀ ) Current transformer Goyle LF and energy storage coil
In order to apply current to LS ₁ and LS ₂ , excitation time T ₀
Previously, the bean breaker switches S ₁ , S ₂ , and S ₃ were closed, and the backflow prevention switches S ₄ , S ₅ and the dosing device MS _{0 were} closed.
Leave it open. After completion of the preparation for energization of the DC power supplies PS ₁ , PS ₂ , and PS ₃ , energization is started to be applied to each of the coils LF, LS ₁ , and LS ₂ from the time of −t ₀ to supply a predetermined current.

Excitation of each coil is performed as follows.

The LF coil is excited by the DC power supply PS ₁ , S ₁
→Power is applied via LF and R. In this case, it is possible to connect a switch element in series with the variable resistor R for adjusting the time constant to block the current flow.

The LS ₁ coil is excited by the DC power supply PS ₂ S ₂
→Power through LS ₁ .

The LS ₂ coil is excited by the DC power supply PS ₃ .
Power is applied via S ₃ → LS ₂ .

(ii) Plasma current excitation time (T ₁ ) At the time of t=0, the damping switch S ₁ is turned off to cut off the DC current supplied from the DC power supply device PS ₁ . The current in the air-core current transformer coil LF is attenuated via the variable resistor R. In this case, the current I of the coil LF is connected to the terminals of the resistor R and the coil LF.
A voltage drop occurs due to the resistance r of the resistor R,
A voltage of r·I is generated. Meanwhile, current transformer coil
Since the LF and the plasma circuit are closely coupled electromagnetically and there is a mutual inductance M, a voltage is induced in the plasma circuit by the product of the current attenuation dI/dt and the mutual inductance M. . If the plasma circuit breaks down due to this voltage and plasma is formed, a plasma current flows based on the principle of a transformer.

Next, after a certain period of time has elapsed, the cut-off switch _S2 is turned off to cut off the current from the DC power supply _PS2 .
In this case, if a thyristor element is used as a power source for the DC power supply PS ₂ , a bypass pair operation is performed or the control angle (α) is set to around 90°. Such control can have the same effect as a short circuit on the DC side, which is not directly related to the AC side of the rectifier (PS ₂ ).

At the same time as turning off the heat cutoff switch _S2 , turn on the heat cutoff switch _S4 .

By the above operation, energy storage coil LS ₁
The current attenuates through PS ₂ →R and LF→S ₄ .
Since this current flows through the current transformer coil LF in a direction opposite to the attenuation current, the current in the current transformer coil LF is further attenuated, and in some cases, the direction of the current may be reversed. However, since the direction of the current change does not change, the plasma circuit has an energy storage coil.
It is possible to have the same effect as if energy was supplied by the current of LS ₁ .

After turning off switch S ₂ , turn off switch S ₃
Turn off the switch and turn on the switch _S5 . The current in coil LS ₂ supplies energy to the plasma circuit in a similar manner to coil LS ₁ .

In this way, by switching on or off the switches S ₁ , S ₂ , and S ₃ , the current in the current transformer coil LF changes in a certain direction, and the plasma circuit is more affected than when only the coil LF is used. Supply a large amount of energy to generate a plasma current. However, without the operation described below, the plasma current will immediately decay.

(iii) Plasma control and maintenance time (T ₂ ) After the plasma current has sufficiently risen, it is necessary to keep the plasma current constant.

The resistance of the plasma circuit is closely related to the plasma current, and after the plasma current has started up, the resistance becomes extremely low. In other words, plasma can be maintained by supplying a small amount of energy from the current transformer coil side. Therefore, in order to maintain the plasma, it is sufficient to supply a substantially uniform current change rate to the air-core current transformer coil using an external power source. Such supply is carried out in the following manner.

Close the input device MS ₀ when the plasma current reaches the maximum. The DC power supply device PS ₂ is controlled by a control device capable of constant current control by detecting the peak value of the plasma current and the plasma current.

That is, since it is necessary to cause the current change in the air-core current transformer coil LF to flow in the opposite direction to the current generated by the DC power supply device PS ₁ , the DC power supply device PS ₂ is connected in advance so as to be able to conduct current in that direction.

For this reason, the DC power supply device PS ₂ is connected so as to have opposite polarity to PS ₁ and PS ₃ . In such a state, the current of coil LS ₁ was passed through DC power supply PS ₂ to current transformer coil LF during plasma excitation, so after plasma excitation, DC power supply
By generating the PS ₂ voltage, the current transformer coil experiences a current change (dI/
dt). At this time, if the closing device MS ₀ is not turned on, the current must flow through the coils LS ₁ and S ₄ , resulting in a large circuit loss, so the coil LS ₁ and the switch S ₄ are required to have a large current carrying capacity. be done. In order to eliminate these inconveniences, the coil LS ₁ and switch S ₄ are short-circuited using the input device MS ₀ , and the DC power supply PS ₂ is directly connected to the air-core current transformer coil LF to facilitate control. do.

As described above, the power supply device MS ₀ and the DC power supply device PS ₂ enable easy reconnection of the power supply. An economical circuit configuration can be achieved without impairing the characteristics of the power supply circuit.

(iv) Blasma stop time (T ₃ ) This is controlled by the DC power supply PS ₂ .

Although one embodiment of the present invention has been described above,
The present invention is not limited only to the above embodiments, and various modifications can be made. For example, as shown in FIG. 5, in order to cause current to flow directly from energy storage coil LS ₁ to current transformer coil LF without passing current to DC power supply device PS ₂ during plasma excitation time, coil LS ₁ A stopping switch, such as a diode D, can be connected in series with this.

As explained above, the current transformer power supply circuit according to the present invention has the following effects.

(i) The circuit configuration of the air-core current transformer coil power supply is simple.

(ii) The circuit is reliable because it has fewer components.

(iii) The circuit is more economical than conventional methods.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram of current transformer coil current and plasma current, Fig. 2 is a connection diagram showing a conventional current transformer power supply circuit, Fig. 3 is a connection diagram showing an embodiment of the present invention, and Fig. 4 3 is a signal waveform diagram showing the operation sequence of the embodiment of FIG. 3, and FIG. 5 is a connection diagram showing a modification of the present invention. PS ₁ , PS ₂ , PS ₃ ...DC power supply, LF...Air core current transformer coil, LS ₁ , LS ₂ ...Energy storage coil for plasma current excitation, R...Variable resistor for time constant adjustment, S ₁ , S ₂ , S ₃ ...Shield disconnection switch
S ₄ , S ₅ ... Switch for preventing backflow of energy storage coil current, MS ₀ ... Closing device, D ... Diode.

Claims (1)

[Claims] 1. In a current transformer power supply circuit used in a tomakaku-type nuclear fusion device to ignite, excite, and maintain control of plasma, the plasma circuit is ignited and excited by generating high voltage. an air-core current transformer coil that flows through the air-core current transformer coil, an energy storage coil that stores the current that flows through the air-core current transformer coil to generate a high voltage, and a connection that supplies DC current to the air-core current transformer coil and the energy storage coil, respectively. a plurality of DC power supply devices, one of which is connected with opposite polarity, and a plurality of DC power supply devices, one of which is connected after plasma ignition, so as to cause the current accumulated in the energy storage coil to flow in the opposite direction of the decay current of the current transformer coil. a switch circuit that connects the energy storage coil and the air-core current transformer coil; and a switch that connects the reverse-polarity-connected DC power supply directly to the air-core current transformer coil by switching after the plasma current has sufficiently risen. and a current transformer power supply circuit.