Cryogenic magnet power supply

Patent metadata

Field	Value
Publication number	US-11193996-B2
Application number	US-201816482782-A
Country	US
Kind code	B2
Filing date	Feb 7, 2018
Priority date	Feb 9, 2017
Publication date	Dec 7, 2021
Grant date	Dec 7, 2021

Abstract

There is described a magnet assembly comprising a superconducting coil, a cryogenic system, a DC voltage source, an SMPS, current leads, and a controller. The cryogenic system comprises a cryostat and is configured to maintain the superconducting coil at an operating temperature below the critical temperature of the superconductor. The DC voltage is source located outside the cryostat. The SMPS is located inside the cryostat and configured to supply power from the DC voltage source to the superconducting coil. The SMPS comprises a voltage step-down transformer having a primary and a secondary winding. The current leads connect the DC voltage source to the SMPS. The controller is configured to cause the SMPS to supply a first amount of power to the magnet in order to ramp up the magnet to operating current, and a second amount of power to the magnet during steady state operation of the magnet, wherein the first amount of power is greater than the second amount of power.

First claim

The invention claimed is:

1. A magnet assembly comprising:
a superconducting coil;
a cryogenic system comprising a cryostat and configured to maintain the superconducting coil within the cryostat at an operating temperature below the critical temperature of the superconductor;
a DC voltage source located outside the cryostat;
a switched mode power supply, SMPS, located inside the cryostat and configured to supply power from the DC voltage source to the superconducting coil, the SMPS comprising a voltage step-down transformer having a primary and a secondary winding;
current leads connecting the DC voltage source to the SMPS;
and a controller configured to cause the SMPS to supply a first amount of power to the magnet in order to ramp up the magnet to operating current, and a second amount of power to the magnet during steady state operation of the magnet, wherein the first amount of power is greater than the second amount of power.

2. A magnet assembly according to claim 1 , wherein said transformer has non-isolated windings.

3. A magnet assembly according to claim 1 , wherein said transformer has isolated windings.

4. A magnet assembly according to claim 1 , wherein the transformer comprises a core of magnetically permeable material which links the windings.

5. A magnet assembly according to claim 1 , wherein the transformer has an air core.

6. A magnet assembly according to claim 1 , wherein the controller is configured to cause the SMPS to operate on a first duty cycle in order supply the first amount of power, and on a second duty cycle in order to supply the second amount of power, wherein the first duty cycle is greater than the second duty cycle.

7. A magnet assembly according to claim 1 , wherein the controller is configured to cause the DC voltage source to supply a first voltage to the SMPS in order supply the first amount of power and a second voltage to the SMPS in order to supply the second amount of power, wherein the first voltage is greater than the second voltage.

8. A magnet assembly according to claim 1 , wherein the superconducting coil acts as an energy storage inductor of the SMPS.

9. A magnet assembly according to claim 1 , wherein at least the secondary winding of said transformer comprises superconducting material, and the cooling system is configured to maintain the superconducting material at or below a critical temperature of the superconducting material.

10. A magnet assembly according to claim 9 , wherein the secondary winding of said transformer comprises a high temperature superconductor HTS.

11. A magnet assembly according to claim 1 , wherein said SMPS has a topology which is one of:
a forward converter;
a push-pull converter;
a half bridge converter; and
a full-bridge converter.

12. A magnet assembly according to claim 1 , wherein the switching speed of the SMPS is less than or equal to 1 kHz, more preferably less than or equal to 100 Hz, more preferably less than or equal to 10 Hz.

13. A magnet assembly according to claim 1 , wherein the controller is configured to monitor current in the superconducting coil and to adjust the second amount of power supplied to the SMPS in order to maintain a substantially constant current in the superconducting coil when the magnet is in steady state operation.

14. A magnet assembly according to claim 1 , wherein the superconducting coil comprises one or both of high temperature superconductor, HTS, and low temperature superconductor, LTS.

15. A magnet assembly comprising:
a superconducting coil;
a cryogenic system comprising a first cryostat configured to maintain the superconducting coil at an operating temperature below the critical temperature of the superconductor and a second cryostat configured to maintain a temperature between room temperature and the operating temperature, wherein the superconducting coil is within the first cryostat;
a DC voltage source located at room temperature;
a switched mode power supply, SMPS, configured to supply power from the DC voltage source to the superconducting coil, the SMPS comprising a voltage step-down transformer having a primary and a secondary winding, wherein the SMPS is located in the second cryostat;
first current leads connecting the DC voltage source to the SMPS;
second current leads connecting the SMPS to the magnet; and
a controller configured to cause the SMPS to supply a first amount of power to the magnet in order to ramp up the magnet to operating current, and a second amount of power to the magnet during steady state operation of the magnet, wherein the first amount of power is greater than the second amount of power.

16. A magnet assembly comprising:
a superconducting coil;
a cryogenic system comprising a cryostat and configured to maintain the superconducting coil within the cryostat at an operating temperature below the critical temperature of the superconducting coil;
a DC voltage source located outside the cryostat;
a switched mode power supply, SMPS, configured to supply power from the DC voltage source to the superconducting coil, the SMPS comprising a voltage step-down transformer having a primary and a secondary winding, wherein the primary winding is located outside the cryostat and the secondary winding is located inside the cryostat;
current leads connecting the DC voltage source to the SMPS;
current leads connecting the secondary winding to the magnet;
and a controller configured to cause the SMPS to supply a first amount of power to the magnet in order to ramp up the magnet to operating current, and a second amount of power to the magnet during steady state operation of the magnet, wherein the first amount of power is greater than the second amount of power.

17. A magnet assembly according to claim 16 , wherein said transformer is air cored and is a resonant transformer.

18. A magnet assembly according to claim 16 , wherein said transformer comprises a core of magnetically permeable material which links the windings and which penetrates a wall of the cryostat.

19. A magnet assembly according to claim 18 , wherein said core is formed from any one of:
iron;
amorphous steel; and
ferrite.

20. A method of providing power to a superconducting coil of a magnet assembly, wherein the magnet assembly comprises a cryostat in which the superconducting coil is provided, the method comprising:
providing a switched mode power supply, SMPS, wherein the SMPS comprises a voltage step-down transformer having a primary winding and a secondary winding, and the secondary winding is inside the cryostat of the magnet assembly;
energizing the magnet by supplying a first amount of power from a DC voltage source outside the cryostat to the coil via the SMPS; and
maintaining steady state operation of the magnet by supplying a second amount of power from the DC voltage source to the coil via the SMPS;
wherein the first amount of power is greater than the second amount of power.

21. A method according to claim 20 , wherein the SMPS operates on a first duty cycle in order to supply the first amount of power, and a second duty cycle in order to supply the second amount of power, and the first duty cycle is less than the second duty cycle.

22. A method according to claim 20 , wherein the DC voltage source provides a first voltage in order to supply the first amount of power, and a second voltage in order to supply the second amount of power, wherein the first voltage is less than the second voltage.

23. A met

Assignees

• Tokamak Energy Ltd

Inventors

• Slade Robert

Classifications

• H01F6/008 Primary

  Electric circuit arrangements for energising superconductive electromagnets · CPC title

• H01F6/06

  Coils, e.g. winding, insulating, terminating or casing arrangements therefor · CPC title

• H02H7/001

  for superconducting apparatus, e.g. coils, lines, machines · CPC title

• H01F6/065

  Feed-through bushings, terminals and joints (leading of conductors or axles through casings of transformers H01F27/04) · CPC title

• H01F6/04

  Cooling · CPC title