JPS59218710A - Superconductive electromagnet device - Google Patents

Abstract

PURPOSE:To contrive prevention of burning of an electromagnet by a method wherein a bidirectional constant voltage element such as a varistor and the like is used as a discharge element, thereby enabling to prevent generation of a branching-off to the discharge element even when said element is being excited or demagnetized. CONSTITUTION:A bidirectional constant voltage element 8 such as a varistor and the like is used as a discharge element instead of a resistor 1 and a diode 2. The operating voltage of said constant voltage element 8 is selected in such a manner that it will be a little higher than the exciting or demagnetizing voltage of the electromagnet. As a result, no branching-off is generated on the discharge element 8 when it is excited or demagnetized, and no heat is generated. When an OFF position is given to a superconductive switch 4 and the electromagnet is quenched, a voltage is generated at both ends of the electromagnet, the discharge element is turned to a constant-voltage resistor, and the magnetic energy of the electromagnet is absorbed by said constant-voltage resistor. An electric discharge is generated in the state of constant voltage, the current on the electromagnet is reduced rectilinearly as time elapses.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to an energizing system for a superconducting electromagnet device. In this superconducting electromagnet device, discharge resistors were installed at both ends of the electromagnet in the cryogenic part in order to release the magnetic energy of the electromagnet outside the electromagnet when the superconducting electromagnet quenched. However, in this case, a shunt current flows through the discharge resistor etc. due to the voltage generated across the electromagnet during excitation or demagnetization.

There were problems such as heat generation and evaporation of the cryogenic refrigerant. To solve this problem, there is a method of inserting a diode in series with the discharge resistor, but since the diode is a unidirectional element, it is only effective during excitation or demagnetization, and this method is not effective for both excitation and demagnetization. .

[Object of the Invention] An object of the present invention is to provide a device that can prevent current from being shunted to a discharge element even during excitation and demagnetization.

[Overview of the Invention] The object of the present invention is achieved by using a bidirectional constant voltage element such as a varistor as a discharge element.

[Effects of the Invention] By carrying out the present invention, it is possible to prevent the evaporation of the low-temperature refrigerant during excitation and demagnetization, and since the discharge is performed at a constant voltage, the discharge time is short and burnout of the electromagnet is prevented. It is also effective for prevention.

[Embodiment of the invention'] Embodiments of the invention will be described based on the drawings.

FIG. 1 shows a conventional example in which a resistor 1 and a diode 2 are used as discharge elements. 3 is an electromagnet, 4 is a superconducting switch, 5 is a detachable current lead, 6 is an excitation power source, and 7 is a cryogenic container.

In this circuit, the shunt to the resistor 1 can be prevented during magnetization, but when demagnetized, a forward voltage is applied to the diode, causing a shunt current to flow and heat generation in the resistor 1. Second
The figure shows a specific embodiment of the present invention in which 1 and 2 are replaced with bidirectional constant voltage elements 8 such as varistors. The operating voltage of this constant voltage element is selected so as to be slightly higher than the excitation and demagnetization voltages of the electromagnet. Then, during excitation and demagnetization, no shunt occurs in the discharge element 8, and no heat is generated. When the electromagnet is quenched, by opening the superconducting switch 4, a voltage is generated across the electromagnet, and the discharge element becomes a constant voltage resistor, which absorbs the magnetic energy of the electromagnet. In this invention, since discharge occurs at a constant voltage, the electromagnet current decreases linearly with time.

In contrast, in the conventional example, the electromagnet current decreases exponentially. Therefore, in the case of the same discharge voltage across both ends of the electromagnet, the electromagnet current decreases faster in the present invention, which is advantageous in terms of protecting the electromagnet from burnout.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, and FIG. 2 is a circuit diagram according to the present invention. 3...Superconducting electromagnet, 4...Superconducting switch. 5... Removable current lead, 8... Bidirectional constant voltage element.

Claims (1)

[Claims] In a superconducting electromagnet device equipped with a superconducting electromagnet, a superconducting switch, a current lead, and a protection circuit element for quenching, the current lead is removable and the protection circuit element for quenching is on the electromagnet side from the current lead attachment/detachment part. A superconducting electromagnet device characterized by being a voltage element.