Current Transformer Core And Method For Producing A Current Transformer Core

• US 20070126546A1
• Filed: 11/17/2006
• Published: 06/07/2007
• Est. Priority Date: 05/17/2004
• Status: Active Grant

• Current Assignee: Vacuumschmelze GmbH & Company KG (Vectra Corp.)
• Original Assignee: Vacuumschmelze GmbH & Company KG (Vectra Corp.)
• Inventors: Guenther, Wulf, Petzold, Joerg, Otte, Detlef
• Granted Patent: US 7,358,844 B2
• Time in Patent Office: Days
• US Class Current: 336/229
• CPC Class Codes: C22C 38/002 containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/12 containing tungsten, tantalum, molybdenum, vanadium, or niobium
• CPC Class Codes: C22C 38/16 containing copper
• CPC Class Codes: H01F 1/15308 based on Fe/Ni H01F1/15325 takes precedence
• CPC Class Codes: H01F 1/15333 containing nanocrystallites, e.g. obtained by annealing
• CPC Class Codes: H01F 27/255 made from particles H01F27/26 takes precedence
• CPC Class Codes: H01F 30/16 Toroidal transformers
• CPC Class Codes: H01F 38/30 Constructions
• CPC Class Codes: H01F 41/0226 from amorphous ribbons
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/49071 by winding or coiling
• CPC Class Codes: Y10T 29/49073 by assembling coil and core
• CPC Class Codes: Y10T 29/49075 including permanent magnet or core
• CPC Class Codes: Y10T 29/49078 Laminated

Abstract

A current transformer core has a ratio of the core outside diameter D_a to the core inside diameter D_i of <1.5, a saturation magnetostriction λ_s of=|4| ppm, a circular hysteresis loop with 0.50=Br/Bs 0.85 and an H_cmax=20 mA/cm. The current transformer core is made of a soft magnetic iron alloy in which at least 50% of the alloy structure is occupied by fine-crystalline particles with an average particle size of 100 nm or less, and the iron-based alloy comprises, in essence, one combination.

Claims

1. A current transformer core comprising a ratio of the core outside diameter D_a to the core inside diameter D_i of <

1.5, a saturation magnetostriction λ

_s≦

|4| ppm, a round hysteresis loop with 0.50≦

Br/Bs≦

0.85 and an H_cmax<

20 mA/cm, whereby the current transformer cores consist of a soft magnetic iron-based alloy in which at least 50% of the alloy structure consists of fine crystalline particles with an average particle size of 100 nm or less and the iron-based alloy has essentially the composition;

(Fe_x-aCo_aNi_b)_xCu_yM_zSi_vB_w

where M denotes an element from the group V, Nb, W, Ta, Zr, Hf, Ti, Mo or a combination thereof and in addition;

x+y+z+v+w=100%, where

Fe+Co+Ni=x=100%−

y−

z−

v−

w

Co a≦

1.5 at %

Ni b≦

1.5 at %

Cu 0.5≦

y≦

2 at %

M z≦

5 at %

Si 6.5≦

v≦

18 at %

B 5≦

w≦

14 at %

wherein v+w>

18 at %.

2. The current transformer core according to claim 1, comprising a saturation magnetostriction λ

_s≦

|2| ppm, a round hysteresis loop with 0.50≦

Br/Bs≦

0.70 and an H_cmax≦

10 mA/cm, whereby the current transformer core is made of a soft magnetic iron-based alloy in which at least 50% of the alloy structure consists of fine crystalline particles with an average particle size of 100 nm or less and the iron-based alloy has essentially the composition;

(Fe_x-aCo_aNi_b)_xCu_yM_zSi_vB_w

where M denotes an element from the group V, Nb, W, Ta, Zr, Hf, Ti, Mo or a combination thereof and in addition;

x+y+z+v+w=100%, where

Fe+Co+Ni=x=100%−

y−

z−

v−

w

Co a≦

0.5 at %

Ni b≦

0.5 at %

Cu 0.75≦

y ≦

1.25 at %

M 2.0≦

z<

3.5 at %

Si 13≦

v≦

16.5 at %

B 5≦

w≦

9 at %

whereby 20≦

v+w≦

25 at %.

3. Current transformer core according to claim 2, comprising a saturation magnetostriction λ

_s≦

|0.8| ppm, a round hysteresis loop with 0.65≦

Br/Bs≦

0.50 and an H_cmax≦

10 mA/cm, whereby the current transformer core is made of a soft magnetic iron-based alloy in which at least 50% of the alloy structure consists of fine crystalline particles with an average particle size of 100 nm or less and the iron-based alloy has the following stoichiometric ratio;

(Fe_x-aCo_aNi_b)xCuyMzSivBw

where M denotes an element from the group V, Nb, W, Ta, Zr, Hf, Ti, Mo or a combination thereof and in addition;

x+y+z+v+w=100%, where

Fe+Co+Ni x=100%−

y−

z−

v−

w

Co a≦

0.5 at %

Ni b≦

0.5 at %

Cu 0.75≦

y≦

1.25 at %

M 2.0≦

z≦

3.5 at %

Si 13≦

v≦

16.5 at %

B 5≦

w≦

9 at %

whereby 20≦

v+w≦

25 at %.

4. The current transformer core according to claim 1, comprising a μ

₄>

90,000.

5. The current transformer core according to claim 1, comprising a μ

_max>

350,000.

6. The current transformer core according to claim 1, comprising a saturation induction B_s≦

1.4 Tesla.

7. The current transformer core according to claim 1, for a current transformer having a phase error <

1°

.

8. The current transformer core according to claim 1, wherein the current transformer core is designed as a ring strip-wound core having at least one primary winding and at least one secondary winding.

9. A method for manufacturing ring-shaped current transformer cores having a ratio of the core outside diameter D_a to the core inside diameter D_i≦

1.5 consisting of a soft magnetic iron-based alloy, whereby at least 50% of the volume of the alloy structure consists of fine crystalline particles having an average particle size of 100 nm or less, comprising the following steps;

a) Preparing an alloy melt;

b) Manufacturing an amorphous alloy strip from the alloy melt by rapid solidification technology;

c) Stress-free winding of the amorphous strip to form amorphous current transformer cores;

d) Heat treatment of the unstacked amorphous current transformer cores in one pass to form nanocrystalline current transformer cores while extensively excluding the influence of magnetic fields.

10. The method according to claim 9, wherein the heat treatment is performed in an inert gas atmosphere 20.

11. The method according to claim 9, wherein the heat treatment is performed in a reducing gas atmosphere.

12. The method according to claim 9, wherein the amorphous strip is coated with electric insulation before winding.

13. The method according to claim 9, wherein the current transformer core is immersed in an insulation medium after winding.

14. The method according to claim 9, wherein the heat treatment of the unstacked amorphous current transformer cores is performed on heat sinks having a high thermal capacity and a high thermal conductivity.

15. The method according to claim 14, wherein a metal or a metallic alloy, a metal powder or a ceramic is provided as the material for the heat sinks.

16. The method according to claim 15, wherein the metal or metal powder is copper, silver or a thermally conductive steel.

17. The method according to claim 15, wherein a ceramic powder is provided as the material for the heat sinks.

18. The method according to claim 15, wherein the ceramic or ceramic powder is magnesium oxide, aluminum oxide or aluminum nitride.

19. The method according to claim 9, wherein the heat treatment is performed in a temperature interval from approx. 440°

C. to approx. 620°

C.

20. The method according to claim 19, wherein a constant temperature is maintained for a period of up to 150 minutes in the heat treatment between 500°

C. and 600°

C.

21. The method according to claim 20, wherein the constant temperature is achieved at a heating rate of 0.1 K/min up to 100 K/min.

22. The method according to claim 19, wherein heating phases in which the heating rate is lower than that of the first heating phase and the second heating phase exist in the heat treatment in the range of 440°

C. and 620°

C.

23. The method according to claim 11, wherein the dwell time in the totality of the annealing zones is between 5 and 180 minutes.

24. The method according to claim 9, for a current transformer having a phase error <

1°

.

25. The method according to claim 24, with μ

₄>

90,000.

26. The method according to claim 25, with μ

_max>

350,000.

27. The method according to claim 24, comprising a saturation induction Bs of 1.1 to 1.4 Tesla.

28. The method according to claim 24, comprising a magnetic total isotropy according to K_tot<

2 J/m³.