Magnetic amplifier choke (magamp choke) with a magnetic core, use of magnetic amplifiers and method for producing softmagnetic cores for magnetic amplifiers

1. A transductor choke for a high frequency application comprising a magnetic core made from a nanocrystalline alloy, wherein the nanocrystalline alloy consists essentially of Fe a Co b Cu c M′ d Si x B y M″ z , wherein M′ signifies an element from the group V, Nb, Ta, Ti, Mo, W, Zr, Hf, or a combination thereof, and wherein M″ signifies an element from group C, P, Ge, As, Sb, In, O, N or a combination thereof, wherein the following conditions shall apply:

a+b+c+d+x+y+z=100%, with a=100%−b−c−d−x−y−z;

0≦b≦15;

0.5≦c≦2;

0.1≦d≦6;

2≦x≦20;

2≦y≦18;

0≦z≦10 and

x+y>18;

and wherein the magnetic core has a hysteresis loop which is as rectangular as possible, a saturation magnetostriction |λ s |<3 ppm, and an effective roughness R a (eff) ranging from 3 to 9%.

2. The transductor choke of claim 1 , wherein the following conditions apply:

0≦b≦0.5,

0.8≦c≦1.2,

2≦d≦4,

14≦x≦17,

5≦y≦12, and

22≦x+y≦24.

3. The transductor choke of claim 1 wherein the saturation magnetostriction is |λ s |<0.2 ppm.

4. The transductor choke of claim 1 wherein the effective roughness R a (eff) ranges from 4 to 7%.

5. The transductor choke of claim 1 , wherein said transductor choke has cyclic magnetization losses (P fe ) of less than 140 watt/kg at a frequency of approximately 100 kHz and an induction amplitude of approximately 0.2 T.

6. A method of producing a magnetic core for a transductor choke of claim 1 , comprising:

Pouring a thin band consisting of an amorphous alloy;

Tension-free winding of the thin band to form a magnetic core;

Heating of the magnetic core to a first targeted temperature, which is above the crystallization temperature of the amorphous alloy, using a heating rate ranging from 1 K/min to 20 K/min;

Keeping the magnetic core at the first targeted temperature for a duration of 8 hours or less;

Cooling the magnetic core to a second targeted temperature, which is below the Curie temperature of the amorphous alloy, with a cooling rate ranging from 1 K/min to 20 K/min;

Keeping the magnetic core at the second targeted temperature for a duration of 8 hours or less under a magnetic longitudinal field H>0.5 kA/m; and

Cooling the magnetic core to ambient temperature.

7. A method of producing a magnetic core for a transductor choke of claim 1 , comprising:

Pouring a thin band consisting of an amorphous alloy;

Tension-free winding of the thin band to form a magnetic core;

Heating of the magnetic core to a first targeted temperature, which is above the crystallization temperature of the amorphous alloy, using a heating rate ranging from 1 K/min to 20 K/min;

Keeping the magnetic core at the first targeted temperature for a duration of 8 hours or less;

Cooling the magnetic core to ambient temperature;

Heating the magnetic core to a second targeted temperature, which is below the Curie temperature of the alloy, and below the crystallization temperature of the amorphous alloy, with a heating rate ranging from 1 K/min to 20 K/min;

Keeping the magnetic core at the second targeted temperature for a duration of 8 hours or less under a magnetic longitudinal field H>0.5 kA/m; and

Cooling the magnetic core to ambient temperature.

8. The method producing a magnetic core of claim 6 wherein the second targeted temperature ranges from 290° C. to 520° C.

9. The method of claim 6 wherein the heating of the magnetic core to the first targeted temperature, keeping the magnetic core at the first targeted temperature, and cooling the magnetic core to the second targeted temperature are performed in a field-free manner.

10. The method of claim 6 , further comprising applying a transverse magnetic field during the heating the magnetic core to the first targeted temperature.

11. The method of claim 10 , further comprising applying a transverse magnetic field during the keeping the magnetic core at the first targeted temperature, the cooling the magnetic core to the second targeted temperature, or both.

12. The method of claim 6 wherein the heating up to the initial targeted temperature takes place at a temperature of approximately 450° C. with a heating rate ranging from 1 K/min to 20 K/min and subsequently with a heating rate of approximately 0.15 K/min.

13. The transductor choke having a magnetic core of claim 1 in use in connection with a switched power supply unit in a motor vehicle power supply system.

14. The transductor choke of claim 1 in use in a high frequency application wherein the transductor choke provides switching behavior with frequencies ranging from 10 kHz to 200 kHz, while having minimal cyclic magnetization losses.

15. A switched power supply unit comprising the transductor choke of claim 1 .

16. The switched power supply unit of claim 15 , which is a switched computer power supply unit.

17. A motor vehicle power supply system comprising the transductor choke of claim 1 .

18. The transductor choke of claim 15 , wherein the cyclic magnetization loss P fe is less than 140 watt/kg at 100 kHz or the equivalent at the operating frequency.

19. The transductor choke of claim 1 , wherein the nanocrystalline alloy has a residual excursion value ΔB RS is less than 0.025 B S .

20. The transductor choke of claim 1 , wherein the nanocrystalline alloy has a uniaxial longitudinal anisotropy K U <10 J/m 3 .

21. The transductor choke of claim 1 , wherein said magnetic core further comprises an electrically isolating layer disposed on at least one surface of the nanocrystalline alloy.

22. The transductor choke of claim 21 , wherein the electrically insulating layer comprises an oxide, acrylate, phosphate, silicate, or chromate of the elements Ca, Mg, Al, Ti, Zr, Hf, or Si.