Quench protection circuit for a superconducting magnet

• US 7,492,556 B2
• Filed: 11/18/2005
• Issued: 02/17/2009
• Est. Priority Date: 02/04/2005
• Status: Expired due to Fees

• Current Assignee: Siemens PLC (Siemens AG)
• Original Assignee: Siemens Magnet Technology Limited (Siemens AG)
• Inventors: Atkins, Andrew Farquhar, Kruip, Marcel Jan Marie
• Primary Examiner(s): Sherry; Michael J
• Assistant Examiner(s): HOANG, ANN THI
• Application Number:
  US11/281,678
• Publication Number:
  US 20060176132A1
• Time in Patent Office: 1,187 Days
• Field of Search: 361/19
• US Class Current: 361/19
• CPC Class Codes: G01R 33/3815 with superconducting coils, e.g. power supply therefor
• CPC Class Codes: H01F 6/02 Quenching; Protection arrangements during quenching protection circuits H02H7/001
• CPC Class Codes: H02H 7/001 for superconducting apparatus, e.g. coils, lines, machines
• CPC Class Codes: Y02E 40/60 Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

Abstract

A quench protection circuit for a superconducting magnet, comprises at least one heater associated with a corresponding coil of the superconducting magnet. The at least one heater is arranged to be driven by an inductor which is connected in series with it and is arranged to derive a voltage from variation in a magnetic field of the superconducting magnet. The at least one heater and the inductor are arranged in a series circuit which further comprises a non-linear positive temperature coefficient resistors.

Claims

1. A quench protection circuit for a superconducting magnet, said quench protection circuit comprising:

at least one heater associated with a corresponding coil of the superconducting magnet;

an inductor which is inductively coupled to derive a voltage from variation in a magnetic field of the superconducting magnet, and is connected in series with the at least one heater for driving the at least one heater in response to variation in said magnetic field of the superconducting magnet; and

;

overcurrent protection means for limiting current which flows through said at least one heater in response to heating of said overcurrent protection means by said current;

wherein said overcurrent protection means comprises a self-heating current limiting element that is arranged in a series circuit with said at least one heater and said inductor; and

wherein said self heating current limiting element comprises a non-linear positive temperature coefficient resistor.

2. The quench protection circuit according to claim 1, herein the at least one heater is arranged in a series circuit which further comprises a diode.

3. A superconducting magnet equipped with a quench protection circuit according to claim 1.

4. An MRI system equipped with a magnet according to claim 3.

5. A method of protecting a superconducting magnet from damage during a quench event, comprising the steps of:

inducing voltage in an inductor as a result of the variation of a magnetic field of the superconducting magnet caused by the quench event;

passing a current resulting from the induced voltage through at least one heater associated with a corresponding coil of the superconducting magnet; and

causing the current to flow through an overcurrent protection element that limits current flow through said at least one heater in response to heating of said overcurrent protection element by said current;

wherein said overcurrent protection device comprises a self-heating time dependent current limiting element that is arranged in a series circuit with said at least one heater and said inductor; and

wherein said self heating time dependent current limiting element comprises a non-linear positive temperature coefficient resistance.

6. A quench protection circuit for a superconducting magnet comprising a plurality of serially connected superconducting coils, said quench protection circuit comprising:

a plurality of serially connected heaters, one such heater being associated with each respective coil of the plurality of superconducting coils;

an inductor which is inductively coupled to derive a voltage from variation in a magnetic field of the superconducting magnet, and is connected in series with the plurality of heaters for driving said heaters in response to said variation in said magnetic field; and

overcurrent protection means for limiting current which flows through said heaters in response to heating of said overcurrent protection means by said current;

wherein

said overcurrent protection means comprises a self-heating current limiting element that is arranged in a series circuit with said heaters and said inductor; and

said self eating current limiting element comprises a non-linear positive temperature coefficient resistor.