Demagnetization using a determined estimated magnetic state

• US 8,934,210 B1
• Filed: 06/28/2012
• Issued: 01/13/2015
• Est. Priority Date: 06/28/2012
• Status: Active Grant

• Current Assignee: US Department of Energy (Government of the United States of America)
• Original Assignee: US Department of Energy (Government of the United States of America)
• Inventors: Denis, Ronald J., Makowski, Nathanael J.
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): BROOKS, ANGELA D
• Application Number:
  US13/535,637
• Time in Patent Office: 929 Days
• Field of Search: 361/143, 361/149
• US Class Current: 361/149
• CPC Class Codes: H01F 13/006 Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material for erasing of information on magnetic record carriers G11B5/00

Abstract

A method for demagnetizing comprising positioning a core within the electromagnetic field generated by a first winding until the generated first electrical current is not substantially increasing, thereby determining a saturation current. A second voltage, having the opposite polarity, is then applied across the first winding until the generated second electrical current is approximately equal to the magnitude of the determined saturation current. The maximum magnetic flux within the core is then determined using the voltage across said first winding and the second current. A third voltage, having the opposite polarity, is then applied across the first winding until the core has a magnetic flux equal to approximately half of the determined maximum magnetic flux within the core.

Claims

1. A method for demagnetizing comprising:

a. providing a core positioned within the electromagnetic field generated by a first winding upon application of a first voltage across said first winding;

b. applying said first voltage across said first winding generating a first electrical current through said first winding until said generated first electrical current is not substantially increasing, thereby determining a saturation current;

c. after said step of applying said first voltage across said first winding, applying a second voltage across said first winding generating a second electrical current through said first winding until said generated second electrical current is approximately equal to the magnitude of said determined saturation current;

the polarity of said second voltage opposite of the polarity of said first voltage;

d. determining, using a processor, a value related to the maximum magnetic flux within said core during said step of applying a second voltage across said first winding using a value relating to the voltage across said first winding and a value relating to said second current;

e. after said step of applying a second voltage across said first winding, applying a third voltage across said first winding generating a third electrical current through said first winding until said core has a value related to the magnetic flux of the core, the same relation as said determined value related to the maximum magnetic flux, approximately half of said determined value related to the maximum magnetic flux within said core;

the polarity of said third voltage opposite of the polarity of said second voltage, thereby demagnetizing said core;

f. said step of applying a second voltage across said first winding comprises applying a second voltage across said first winding;

said second voltage having a magnitude equal to the magnitude of the first voltage;

g. said step of determining the a value related to the maximum magnetic flux within said core comprises;

i. multiplying said determined saturation current by approximately 0.6 determining a two-tau saturation current; and

ii. during said step of applying a second voltage across said first winding, timing the amount of time for said second electrical current to reach the approximate magnitude of said two-tau saturation current thereby determining a saturation time; and

h. said step applying a third voltage across said first winding comprising;

i. determining a half saturation time by dividing said timed two-tau saturation time by two; and

ii. applying said third voltage across said first winding for said half saturation time.

2. The method for demagnetizing of claim 1 further comprising:

a. said step of multiplying said determined saturation current by approximately 0.6 determining a two-tau saturation current comprises multiplying said determined saturation current by approximately 0.632 determining a two-tau saturation current.

3. The method for demagnetizing of claim 2 further comprising:

a. determining the electrical resistance across said first winding by dividing said first applied voltage by said first electrical current; and

b. comparing said determined electrical resistance to a known dataset of corresponding to said transformer to determine one or more health characteristics of said transformer.

4. The method for demagnetizing of claim 2 further comprising:

a. during said step of applying said first voltage across said first winding, determining the electrical resistance across said first winding by dividing the voltage across the first winding by said first electrical current;

b. comparing said determined electrical resistance to a known dataset of corresponding to said core to determine one or more health characteristics of said core; and

whereby

c. said provided core further comprises a second winding electrically shorted; and

d. said provided core comprises a network transformer.

5. The method for demagnetizing of claim 4 whereby:

a. said provided core comprises a three-phase network transformer; and

b. said processor comprises a CPU (Central Processing Unit), microcontroller ASIC (Application Specific Integrated Circuit), or a combination thereof.

6. The method for demagnetizing of claim 5 further comprising:

a. said step of multiplying said determined saturation current by approximately 0.6 determining a two-tau saturation current comprises multiplying said determined saturation current by approximately 0.632 determining a two-tau saturation current.

7. A method for demagnetizing comprising:

a. providing a core positioned within the electromagnetic field generated by a first winding upon application of a first voltage across said first winding;

b. applying said first voltage across said first winding generating a first electrical current through said first winding until said generated first electrical current is not substantially increasing, thereby determining a saturation current;

c. after said step of applying said first voltage across said first winding, applying a second voltage across said first winding generating a second electrical current through said first winding until said generated second electrical current is approximately equal to the magnitude of said determined saturation current;

the polarity of said second voltage opposite of the polarity of said first voltage;

d. determining, using a processor, a value related to the maximum magnetic flux within said core during said step of applying a second voltage across said first winding using a value relating to the voltage across said first winding and a value relating to said second current;

e. after said step of applying a second voltage across said first winding, applying a third voltage across said first winding generating a third electrical current through said first winding until said core has a value related to the magnetic flux of the core, the same relation as said determined value related to the maximum magnetic flux, approximately half of said determined value related to the maximum magnetic flux within said core;

the polarity of said third voltage opposite of the polarity of said second voltage, thereby demagnetizing said core;

f. determining the electrical resistance across said first winding by dividing said first applied voltage by said first electrical current; and

g. comparing said determined electrical resistance to a known dataset of corresponding to said transformer to determine one or more health characteristics of said transformer.

8. The method for demagnetizing of claim 7 whereby:

a. said step of determining a value related to the maximum magnetic flux within said core comprises;

i. measuring the electrical current through said first winding during said application of said second voltage; and

ii. calculating a value related to the integral of the voltage across said first winding with respect to time minus a value related to the integral of the product of the winding resistance and the electrical current through the first winding with respect to time, thereby determining a value related to the maximum magnetic flux; and

b. said step applying a third voltage across said first winding comprises;

i. calculating a value related to the integral of the voltage across said first winding with respect to time minus a value related to the integral of the product of the winding resistance and the electrical current through the first winding with respect to time, thereby determining a value related to the magnetic flux of said core.

9. The method for demagnetizing of claim 8 further comprising:

a. measuring the voltage across said first winding during said application of said second voltage; and

whereby

b. said step of calculating a value related to the integral of the voltage across said first winding with respect to time comprises calculating a value related to the integral of said measured voltage across said first winding with respect to time.

10. The method for demagnetizing of claim 8 whereby:

a. said step of applying a second voltage comprises applying a second voltage having a predetermined constant second voltage output; and

b. said step of calculating a value related to the integral of the voltage across said first winding with respect to time comprises calculating a value related to the integral of said predetermined constant second voltage output with respect to time.

11. A method for demagnetizing comprising:

a. providing a core positioned within the electromagnetic field generated by a first winding upon application of a first voltage across said first winding;

b. applying said first voltage across said first winding generating a first electrical current through said first winding until said generated first electrical current is not substantially increasing, thereby determining a saturation current;

c. after said step of applying said first voltage across said first winding, applying a second voltage across said first winding generating a second electrical current through said first winding until said generated second electrical current is approximately equal to the magnitude of said determined saturation current;

the polarity of said second voltage opposite of the polarity of said first voltage;

d. determining, using a processor, a value related to the maximum magnetic flux within said core during said step of applying a second voltage across said first winding using a value relating to the voltage across said first winding and a value relating to said second current;

e. after said step of applying a second voltage across said first winding, applying a third voltage across said first winding generating a third electrical current through said first winding until said core has a value related to the magnetic flux of the core, the same relation as said determined value related to the maximum magnetic flux, approximately half of said determined value related to the maximum magnetic flux within said core;

the polarity of said third voltage opposite of the polarity of said second voltage, thereby demagnetizing said core;

f. during said step of applying said first voltage across said first winding, determining the electrical resistance across said first winding by dividing the voltage across the first winding by said first electrical current; and

g. comparing said determined electrical resistance to a known dataset of corresponding to said core to determine one or more health characteristics of said core.

12. The method for demagnetizing of claim 11 further comprising:

a. measuring the first voltage across said first winding; and

whereby

b. said step of determining the electrical resistance across said first winding by dividing the voltage across the first winding by said first electrical current comprises determining the electrical resistance across said first winding by dividing said measured first voltage across the first winding by said first electrical current.

13. The method for demagnetizing of claim 11 further whereby:

a. said step of determining the electrical resistance across said first winding by dividing the voltage across the first winding by said first electrical current comprises determining the electrical resistance across said first winding by dividing said first voltage by said first electrical current.

14. The method for demagnetizing of claim 11 whereby:

a. said step of determining a value related to the maximum magnetic flux within said core comprises;

i. measuring the electrical current through said first winding during said application of said second voltage; and

ii. calculating a value related to the integral of the voltage across said first winding with respect to time minus a value related to the integral of the product of the winding resistance and the electrical current through the first winding with respect to time, thereby determining a value related to the maximum magnetic flux; and

b. said step applying a third voltage across said first winding comprises;

i. calculating a value related to the integral of the voltage across said first winding with respect to time minus a value related to the integral of the product of the winding resistance and the electrical current through the first winding with respect to time, thereby determining a value related to the magnetic flux of said core.

15. The method for demagnetizing of claim 14 whereby:

c. said provided core further comprises a second winding electrically shorted; and

d. said provided core comprises a network transformer.

16. The method for demagnetizing of claim 14 further comprising:

a. measuring the voltage across said first winding during said application of said second voltage; and

whereby

b. said step of calculating a value related to the integral of the voltage across said first winding with respect to time comprises calculating a value related to the integral of said measured voltage across said first winding with respect to time.

17. The method for demagnetizing of claim 16 whereby:

c. said provided core further comprises a second winding electrically shorted; and

d. said provided core comprises a network transformer.

18. The method for demagnetizing of claim 17 whereby:

a. said provided core comprises a three-phase network transformer; and

b. said processor comprises a CPU (Central Processing Unit), microcontroller ASIC (Application Specific Integrated Circuit), or a combination thereof.

19. The method for demagnetizing of claim 14 whereby:

a. said step of applying a second voltage comprises applying a second voltage having a predetermined constant second voltage output; and

b. said step of calculating a value related to the integral of the voltage across said first winding with respect to time comprises calculating a value related to the integral of said predetermined constant second voltage output with respect to time.

20. The method for demagnetizing of claim 19 whereby:

c. said provided core further comprises a second winding electrically shorted; and

d. said provided core comprises a network transformer.

21. The method for demagnetizing of claim 20 whereby:

a. said provided core comprises a three-phase network transformer; and

b. said processor comprises a CPU (Central Processing Unit), microcontroller ASIC (Application Specific Integrated Circuit), or a combination thereof.