JPH0216109B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply device for coil excitation that uses a thyristor rectifier and has a small ripple voltage.

When superconducting wires are cooled to an extremely low temperature of around -270°C, their direct current resistance becomes zero and they do not generate Joule heat, so they can be used in electromagnets and magnetic confinement nuclei in particle accelerators that require large currents to flow and create high magnetic flux densities. It is used as the electric wire for the toroidal magnetic field coil of the fusion device. Since the direct current resistance of the superconducting coil circuit is very small, its time constant is very large, and as shown in Figure 1, even if the superconducting coil 1 is directly connected to the thyristor rectifier 2, which contains many voltage ripples, the current Almost no ripples occur.
However, when an AC voltage is applied to a superconducting wire, heat is generated due to AC loss, and the temperature of the strands rises, potentially causing a partial or wide transition from the superconducting state to the normal conducting state. The power supply is required to have a very small voltage ripple even though the time constant of the load is very large.

FIG. 2 is an example of a conventionally used excitation power supply device for superconducting coils. In Figure 2,
When the thyristor rectifier 2 is composed of a three-phase bridge rectifier circuit, this output voltage waveform is
The result is as shown in the figure, which includes voltage ripples as shown by diagonal lines. In FIG. 2, this voltage ripple is absorbed by the emitter-collector voltage (V _CE ) of the transistor 3, thereby suppressing the voltage ripple applied to the superconducting coil 1, which is a load, to a low level. In general, transistors have a faster control response than thyristors, so in Figure 2, taking advantage of this feature, transistor 3 performs high-speed voltage control, while thyristor rectifier 2 controls the voltage of transistor 3 at a slower response speed. The average value of _CE is controlled. That is, the current I _L of the superconducting coil 1 is detected by the current detector 4, and the current control unit 5 compares it with the current reference value Iref and outputs the voltage reference signal Vref according to the deviation, and the transistor voltage control unit 6 drives the base current of the transistor 3 according to the deviation between this voltage reference signal Vref and the load side voltage V _L of the transistor 3 detected by the voltage detector 7, so that the load side voltage V _L changes to the voltage reference signal Vref. controlled to match. In addition, the voltage reference signal
The reason why the detected value of the load current is necessary to obtain Vref is as follows.

When the load current I _L is smaller than the current reference value Iref, the output of the transistor voltage control unit 6 is increased to increase the base current, and the collector-emitter voltage V _CE of the transistor 3 is decreased, so that the It is necessary to reduce the voltage drop and increase the voltage V _L applied to the load. Conversely, if the load current I _L is larger than the current reference value Iref,
It is necessary to reduce the voltage _VL applied to the load by reducing the base current of transistor 3 and increasing the collector-emitter voltage _VCE .

A technique in which the output (Vref) of the main controller (current control section 5 in the case of the present invention) is input to the minor loop (transistor voltage control section 6 in the case of the present invention) in this way is already known. On the other hand, in the thyristor voltage control unit 8, a value obtained by adding the operation reference value V _CE ref of V _CE of the transistor 3 to the voltage reference signal Vref and the voltage of the transistor 3 detected by the voltage detector 9 are calculated.
The output voltage is controlled by changing the firing phase of the thyristor rectifier 2 according to the deviation from the power supply voltage Vs, and the average value of V _CE of the transistor 3 is set to the operating reference value.
V _CE ref. As for the control response, the transistor voltage control loop is made the fastest, and the thyristor voltage control loop is made the second fastest.

Since the response frequency of the transistor voltage control loop can be several KHz, even if the output voltage of the thyristor rectifier 2 contains ripples, the load side voltage V _L of the transistor 3 will contain almost no voltage ripples. can be controlled.

However, in the circuit shown in FIG. 2, the current I _L of the superconducting coil 1 flows through the transistor 3, and in the case of a large superconducting coil, the current I L will be several tens of KA, making the transistor power supply extremely expensive.

The present invention has been made in view of this point,
By connecting the primary winding of the transformer to the main circuit and connecting the transistor to the secondary winding of this transformer, the large current output of the thyristor rectifier can be controlled without passing the load current of the superconducting coil through the transistor. The present invention provides an inexpensive, highly reliable, and rational DC power supply device for coil excitation that absorbs voltage ripples.

An embodiment of the present invention is shown in FIG. The differences in configuration between the conventional system shown in Fig. 5 and Fig. 2 are as follows.
The primary winding of a transformer 10 is connected in series with the superconducting coil 1, and the transistor 3 is connected to the secondary winding side of the transformer 10. With such a configuration, the DC component of the current I _L of the superconducting coil 1 does not flow into the secondary winding side of the transformer 10. transformer 1
If the turns ratio of 0 (number of secondary windings/number of primary windings) is n, and the voltage ripple value (O-P) generated by the thyristor rectifier 2 is Vrip, then the transistor 3 is as shown in FIG. In the case of a class A amplifier,
The voltage rating can be determined from 2nVrip, and the current rating can be determined based on the excitation current required for the transformer 10 to generate this much voltage.

Next, the configuration and operation of the control circuit in the present invention will be explained. The control circuit of the present invention shown in FIG. 5 is the same as the control circuit of the conventional excitation power supply device shown in FIG. 2 in controlling the base current of the transistor 3, but the control circuit of the thyristor rectifier 2 is different. That is, in FIG. 5, the secondary current I ₂ of the transformer 10 is detected by the current detector 11, and the average value of this secondary current I ₂ becomes the operating reference value I _CB ias of the collector current of the transistor 3. The output voltage of the thyristor rectifier 2 is controlled as follows.

The operation of the control circuit will be explained in more detail below. The current I _L of the superconducting coil 1 is detected by a current detector 4, and the current control unit 5 compares it with a current reference value Iref, and outputs a voltage reference signal Vref according to the deviation. The transistor voltage control unit 6 drives the base current of the transistor 3 according to the deviation between the voltage reference signal Vref and the load side voltage V _L detected by the voltage detector 7, thereby controlling the voltage between the transistor power supply 20 and the transformer. A secondary current I ₂ is passed through a closed circuit consisting of 10 secondary windings, current detector 11 and transistor 3. This current becomes the excitation current of the transformer 10 and generates a voltage on the primary winding side of the transformer 10, so that V _L
Acts to approach Vref. On the other hand, the voltage reference signal Vref is applied as a first input signal to the thyristor voltage control unit 8 with a polarity such that when it increases, the output voltage of the thyristor rectifier 2 increases, and the voltage detector 9 is applied to the thyristor voltage control section 8 as a second input signal with a polarity opposite to that of the voltage reference signal Vref. Furthermore, the amount obtained by adding a certain bias value I _CB ias to the detected value of the current I ₂ is the amount that is calculated by the secondary current control unit 1.
2, and this output signal Vref ₂ is applied as a third input signal to the thyristor voltage control section 8 with the same polarity as the first input signal. Both the voltage reference signal Vref and the secondary current _I2 are
Since it is added to the thyristor voltage control unit 8 with a positive sign, when the secondary current I ₂ increases, the third input signal (Vref ₂ ) to the thyristor voltage control unit 8 increases, and the output voltage of the thyristor rectifier 2 increases. As the voltage increases, the load side voltage V _L of the transformer 10 also increases. this
The increase in V _L is detected by the voltage detector 7, and the input signal to the transistor voltage control unit 6 acts in the direction of decreasing, so the base current of the transistor 3 decreases and the secondary current I ₂ of the transformer 10 decreases. Said bias value
It decreases and equilibrates until it equals I _CB ias. Fifth
In the figure as well, the transistor voltage control loop is the fastest and the thyristor voltage control loop is the second fastest in terms of response speed. Further, the response speed of the secondary current control loop (the control loop including the secondary current control section 12 as the main loop) is made the third fastest. By doing so, the transistor 3 controls the load side voltage V _L to be equal to the voltage reference signal Vref at high speed, while the thyristor rectifier 2 controls the secondary current I ₂ of the transformer 10 (this is the The average value of the collector current I _C (equal to the collector current I C ) can be controlled to be a preset value I _{C B} ias.
Moreover, since the transistor voltage control loop has a very fast response, it can be controlled so that the voltage ripple generated by the thyristor rectifier 2 is almost not included in the load side voltage _VL .

Next, another embodiment of the present invention is shown in FIG. Fifth
In the figure, the transformer 10 is directly connected to the output of the thyristor rectifier 2 without a filter, but in FIG. 6, a filter 30 is provided between the thyristor rectifier 2 and the transformer 10. In this way, the voltage ripple to be controlled by the transistor 3 is reduced by the action of the filter 30, and the capacitance of the transistor 3 can be reduced.

Furthermore, FIG. 7 shows another embodiment of the present invention, in which the embodiment of FIG. 5 uses the transistor 3 as a class A amplifier that operates around point A in FIG. In FIG. 7, it is configured as a class B push-pull amplifier so that the secondary side bias current of the transformer 10 does not need to flow. Therefore, in FIG. 7, it is not necessary to apply the bias value I _CB ias to the input side of the secondary current control section 12.

Although the above description has been made regarding the case of an excitation power supply device for a superconducting coil, the present invention can also be applied to, for example, an excitation power supply device for a normal conduction coil of a particle accelerator that does not want a minute ripple in the magnetic flux density.

As explained above, according to the present invention, by connecting the transistor 3 to the secondary side of the transformer 10 provided in series with the output side of the thyristor rectifier,
It is possible to obtain a rational DC power supply device for coil excitation that sufficiently reduces ripples in the current I _L of the load coil by using a transistor with a very small capacity compared to the conventional system.

[Brief explanation of drawings]

Figure 1 is a general circuit diagram of a coil excitation power supply that does not use transistors, Figure 2 is a circuit diagram of a conventional coil excitation power supply that uses a thyristor rectifier and a transistor, and Figure 3 is the output voltage waveform of the thyristor rectifier. FIG. 4 is an explanatory diagram of the operation of a class A amplifier, and FIGS. 5 to 7 are circuit diagrams showing respective embodiments of the present invention. 1: Load coil, 2: Thyristor rectifier, 3:
Transistor, 5: Current control section, 6: Transistor voltage control section, 8: Thyristor voltage control section, 1
0: Transformer, 12: Secondary current control section.

Claims (1)

[Claims] 1. In a DC power supply device for coil excitation that supplies a smooth DC current to a coil by the output of a thyristor rectifier, the primary winding of a transformer is connected in series with the coil, and a connection is made between the terminals of the secondary winding of this transformer. A transistor and a power supply for the transistor are connected to form a closed circuit, and a current detector is provided to detect the secondary current flowing in this closed circuit, and the current detector is installed to detect the secondary current flowing through the closed circuit. a transistor voltage control section that outputs a transistor base current based on a deviation between the first voltage reference signal and a load-side voltage generated between both ends of the coil; and a secondary current control unit that inputs at least the output of the current detector and outputs a second voltage reference signal, the secondary current control unit receiving at least the output of the current detector and outputting a second voltage reference signal, the voltage being determined by the first and second voltage reference signals and the output voltage of the thyristor rectifier. A direct current for coil excitation, characterized in that a thyristor voltage control section is provided that outputs a firing signal to a thyristor rectifier based on the deviation, and the response speed of the transistor voltage control loop is made faster than the response speed of the thyristor voltage control loop. power supply.