JP2951459B2 - Power supply for superconducting magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device used for exciting and demagnetizing a superconducting magnet.

[0002]

2. Description of the Related Art Excitation and demagnetization of a superconducting magnet are usually performed.
This is performed by a power supply device for a superconducting magnet. That is, when the superconducting magnet is excited, a power supply is connected to the superconducting magnet to supply a current, and when the current reaches a predetermined value, the permanent current switch is turned on (the heater of the permanent current switch is turned off). Then, with the permanent current flowing through the superconducting magnet, the power supply is disconnected.

When demagnetizing a superconducting magnet,
A power supply is connected to the superconducting magnet, and when the supply current of the power supply and the permanent current of the superconducting magnet are balanced, the permanent current switch is turned off (the heater of the permanent current switch is energized and heated). The flowing current is attenuated.

[0004]

As described above, the power supply device for a superconducting magnet is repeatedly connected to and disconnected from the superconducting magnet. Particularly, when the superconducting magnet is demagnetized or its magnetic field is changed, the power supply device is connected to the superconducting magnet. If the polarity is incorrectly connected to the magnet, the superconducting magnet may be quenched, causing a large amount of expensive refrigerant to evaporate, or destroying the rectifier diode, transistor, capacitor, etc. of the power supply unit. Had become.

For this reason, there has been a demand for a power supply device that can safely demagnetize or change the magnetic field even when the superconducting magnet in the excited state is demagnetized or changed in magnetic field even if the polarity is incorrectly connected.

[0006]

SUMMARY OF THE INVENTION The present invention provides a power supply device for a superconducting magnet which solves the above-mentioned problems, and has a structure in which a terminal to which the superconducting magnet is connected and a current output circuit have polarities. Connected via a changeover switch, a short-circuit resistor and a short-circuit switch are connected in series between terminals to which the superconducting magnet is connected, and a voltage detector for detecting the terminal voltage of the short-circuit resistor and its polarity is further provided. A drive circuit for operating the polarity switch when the polarity of the superconducting magnet detected by the voltage detector is different from the polarity of the current output circuit is provided.

[0007]

When demagnetizing or changing the magnetic field of a superconducting magnet in an excited state with this power supply device, first connect this power supply device to the superconducting magnet, close the short-circuit switch, and connect the short-circuit resistance to the superconducting magnet. Then, the permanent current switch is turned off (the heater of the permanent current switch is energized and heated). Then, the current of the superconducting magnet flows through the short-circuit resistor.The polarity of the superconducting magnet is detected by the voltage detector. Switch.

As a result, the polarities of the power supply device and the superconducting magnet become the same. Therefore, if the output current of the current output circuit is increased here, the current flowing through the short-circuit resistor decreases (the detection voltage of the voltage detector). Decreases). When the current flowing through the short-circuit resistance becomes zero, the current flowing from the superconducting magnet becomes equal to the current supplied from the current output circuit. At this point, the short-circuit switch is opened. As a result, the current output circuit and the superconducting magnet are in a directly connected state. After that, as usual, the current of the superconducting magnet is controlled by the set voltage and current of the power supply device,
Demagnetization or magnetic field change may be performed.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention. 11 is a superconducting magnet, 13 is a permanent current switch, 13A is a heater for turning on and off the permanent current switch 13, and 13B is a heater 13
A power supply, 15 is a cryostat. When the superconducting magnet 11 is in the excited state, a permanent current flows through a loop circuit including the superconducting magnet 11 and the permanent current switch 13.

Reference numeral 17 denotes a power supply, 19 denotes a current output circuit, 21
a and 21b are terminals to which the superconducting magnet 11 is connected. The terminals 21a and 21b and the current output circuit 19 are connected via a polarity switch 23. A short-circuit resistor 25 and a short-circuit switch 27 are connected in series between the terminals 21a and 21b, and a voltage detector 29 is connected to both ends of the short-circuit resistor 25.

The voltage detector 29 measures and displays the terminal voltage of the short-circuit resistor 25 and detects the polarity of the voltage. A polarity signal of the voltage (polarity of the superconducting magnet 11) detected by the voltage detector 29 is sent to a drive circuit 31, and the drive circuit 31 operates the polarity switch 23 according to the signal.

Next, a method of demagnetizing the superconducting magnet 11 by the power supply 17 will be described. First, the excited superconducting magnet 11 is connected to the terminals 21a and 21b, and the short-circuit switch
After closing 27, power supply of heater 13A of permanent current switch
Insert 13B. Then, the permanent current switch 13 is turned off, and the current flowing through the superconducting magnet 11 is changed to the short-circuit resistance 25.
Flows to In this state, the voltage detector 29 detects the voltage and polarity at both ends of the short-circuit resistor 25.

If the polarity of the voltage detected by the voltage detector 29 (the polarity of the superconducting magnet 11) is the same as the polarity of the current output circuit 19, the process proceeds to the next step. (The polarity of the current output circuit 19 is made the same as that of the superconducting magnet 11), and the process proceeds to the next step. In the next step, the current output circuit 19 is controlled so that the terminal voltage of the short-circuit resistor 25 becomes zero, and when the terminal voltage of the short-circuit resistor 25 becomes zero, the short-circuit switch 27 is turned off.
By controlling the current output circuit 19, the current of the superconducting magnet 11 is reduced. With this, the superconducting magnet 11 can be demagnetized.

When the magnetic field of the superconducting magnet 11 is changed, the terminal voltage of the short-circuit resistor 25 becomes zero and the short-circuit switch 27 is turned off by the above-described sequence control. Change the current,
When the current reaches the set current, the power supply 13B of the heater 13A of the permanent current switch is turned off to turn on the permanent current switch 13, and then the output current of the current output circuit 19 may be reduced. Exciting the superconducting magnet 11 is the same as in the prior art.

[0015]

As described above, the power supply device according to the present invention can be connected to the superconducting magnet to demagnetize or change the magnetic field regardless of the polarity of the superconducting magnet. When changing the magnetic field, it is possible to eliminate accidents caused by incorrect polarity.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power supply device for a superconducting magnet according to one embodiment of the present invention.

[Explanation of symbols]

11: Superconducting magnet 1
3: Permanent current switch 17: Power supply 1
9: Current output circuit 21a, 21b: Terminal to which superconducting magnet is connected 2
3: Polarity switch 25: Short-circuit resistance 27:
Short-circuit switch 29: Voltage detector 3
1: Drive circuit

Claims (1)

(57) [Claims] 1. A terminal to which a superconducting magnet is connected and a current output circuit are connected via a polarity switch, and a short-circuit resistor and a short-circuit switch are connected in series between terminals to which the superconducting magnet is connected. A voltage detector for detecting the terminal voltage of the short-circuit resistor and the polarity thereof is provided, and a drive circuit for operating the polarity switch when the polarity of the superconducting magnet detected by the voltage detector is different from the polarity of the current output circuit is provided. A power supply device for a superconducting magnet.