Radio Frequency-Assisted Fast Superconducting Switch

• US 20150045228A1
• Filed: 04/09/2013
• Published: 02/12/2015
• Est. Priority Date: 04/11/2012
• Status: Active Grant

• Current Assignee: Brookhaven Science Associates, LLC (Government of the United States of America)
• Original Assignee: Brookhaven Science Associates, LLC (Government of the United States of America)
• Inventors: Solovyov, Vyacheslav, Li, Qiang
• Granted Patent: US 9,837,814 B2
• Time in Patent Office: Days
• US Class Current: 505/191
• CPC Class Codes: H02H 9/023 Current limitation using superconducting elements
• CPC Class Codes: H03K 17/92 by the use, as active elements, of superconductive devices
• CPC Class Codes: H10N 60/355 Power cryotrons
• CPC Class Codes: Y10T 29/49014 Superconductor

Abstract

A radio frequency-assisted fast superconducting switch is described. A superconductor is closely coupled to a radio frequency (RF) coil. To turn the switch “off,” i.e., to induce a transition to the normal, resistive state in the superconductor, a voltage burst is applied to the RF coil. This voltage burst is sufficient to induce a current in the coupled superconductor. The combination of the induced current with any other direct current flowing through the superconductor is sufficient to exceed the critical current of the superconductor at the operating temperature, inducing a transition to the normal, resistive state. A by-pass MOSFET may be configured in parallel with the superconductor to act as a current shunt, allowing the voltage across the superconductor to drop below a certain value, at which time the superconductor undergoes a transition to the superconducting state and the switch is reset.

Claims

1. A superconducting switch, comprising:

a superconductor;

a radio frequency (RF) coil strongly coupled to the superconductor; and

an RF inverter.

2. The superconducting switch of claim 1, wherein the switch is a superconducting fault current limiter.

3. The superconducting switch of claim 1, wherein the superconductor is selected from the group consisting of a superconducting wire, a superconducting tape, and a combination thereof.

4. The superconducting switch of claim 1, wherein the superconductor is superconductive at temperatures above 60 K.

5. The superconducting switch of claim 3, wherein the superconducting tape is made from yttrium barium copper oxide (YBCO;

Tc=93 K) or bismuth strontium calcium copper oxide (BiSCCO;

Bi-2212 has Tc≈

95 K, Bi-2223 has Tc≈

108 K, and Bi-2234 has Tc≈

104K) to form a superconducting layer deposited on a substrate made from nickel, nickel-tungsten alloy, stainless steel, or superalloy.

6. The superconducting switch of claim 3, wherein the RF coil is made from a material that can carry alternating current at frequencies up to about 1 MHz.

7. The superconducting switch of claim 6, wherein the RF coil is made from a race-track shaped RF coil wound from multi-strand Litz wire.

8. The superconducting switch of claim 1, wherein the RF inverter is operable to induce a voltage burst in the RF coil.

9. The superconducting switch of claim 8, wherein the voltage burst in the RF coil is sufficient to induce a current in the superconductor.

10. The superconducting switch of claim 9, wherein the combination of the RF-induced current and other currents present in the superconductor are sufficient to exceed a critical current of the superconductor at an operating temperature.

11. The superconducting switch of claim 1, further comprising:

a by-pass MOSFET coupled in parallel with the superconductor,

wherein the by-pass MOSFET is operable to provide a low-resistance shunt to the superconductor that prevents damage of a superconducting layer during transition of the superconductor into a normal state from a superconducting state and transitionion from the normal state into the superconducting state.

12. The superconducting switch of claim 1, wherein a switching time of the superconductor from a superconducting into a normal state is less than about 5 ms.

13. The superconducting switch of claim 12, wherein the switching time of the superconductor from its normal state into its superconducting state is less than about 5 ms.

14. The superconducting switch of claim 1, having an “

off”

resistance of greater than 10 KΩ

.

15. A method of fabricating a fast superconducting switch, the method comprising:

strongly coupling a radio frequency (RF) coil to a superconductor;

connecting the RF coil to an RF inverter, such that

the RF inverter is operable to induce a voltage burst in the RF coil.

16. A method of operating a superconducting switch, the method comprising:

applying a high-frequency voltage burst to a radio frequency (RF) coil,

wherein the RF coil is strongly coupled to a superconductor,

the superconductor has flowing through it a direct current with a magnitude less than a critical current of the superconductor at an operating temperature,

the voltage burst is sufficient to induce a current in the superconductor, the sum of the induced current and the direct current exceeding the critical current of the superconductor at the operating temperature, and

whereby the superconductor undergoes a transition from a superconducting state to a normal state.

17. The method of claim 16 further comprising:

configuring a by-pass MOSFET in parallel with the superconductor, such that the by-pass MOSFET is operable to shunt current from the superconductor that prevents damage of a superconducting layer during transition of the superconductor into its normal state, and reduces the voltage across the superconductor below a certain value which allows the superconducting switch to become superconducting.

18. The method of claim 17, wherein the transition from the superconducting state into the normal state of the superconductor takes less than about 5 ms.

19. The method of claim 18, wherein when the direct current and the induced current are shunted from the superconductor the critical current of the superconductor is no longer exceeded and the superconductor undergoes a transition into its superconducting state from its normal state.

20. The method of claim 19, wherein the transition into the superconducting state of the superconductor takes less than about 5 ms.