ANOFOL New Insights on Anodized Aluminum Coils, a Copper Alternative

Transcription

1 ANOFOL New Insights on Anodized Aluminum Coils, a Copper Alternative Dr. Oliver Zimmermann Business Unit ANOFOL, Steinert Elektromagnetbau GmbH, D Cologne, Germany zimmermann@anofol.de 1

2 What is Anodizing? And what for? Anodizing is the successful development and control of a natural oxidation process that occurs when aluminum is exposed to the atmosphere. Electricity and chemicals are used jointly to produce a hard, transparent surface that is integral with base aluminum. Aluminum is anodized for corrosion resistance, abrasion resistance, adhesion or aesthetic enhancement or insulation from electricity. Electrochemical process: - 4Al 6(H 2SO4) 2(Al2O3) 6(SO3) 3H 2 ( g) 6H 6e zimmermann@anofol.de 2

3 Insulation Layer by Anodizing Oxide has a cellular structure with a central pore in each cell Uniform hexagonal cell with diameter nm ANOFOL uses continuous coil anodizing Usual Oxide Layer thickness at ANOFOL: 1-6 µm Insulation 20V/µm BDV measured according to DIN EN ISO 2376 Cell Wall Unit Cell Pore Porous Layer Al Al 2 O 3 Interface Aluminium zimmermann@anofol.de 3

4 TEM Figure of Hexagonal Cell Structure Alloying elements do not anodize Aluminum purity larger 99.5% 4

5 Different Microstructures of Al 2 O 3 Layer Side view Top view Porous layer Compact layer zimmermann@anofol.de 5

6 Anodized Aluminum Oxide strip (AAO) Turns of a coil with aluminum strip Aluminum strip with oxide layer covering the whole surface, all around the aluminum strip zimmermann@anofol.de 7

7 Edge Treatment of Aluminum Strip Chamfered egdes, for optimized electrical insulation properties 8

8 Outline ANOFOL Coils Characteristics Advantages Examples 9

9 Mechanical Properties Bulk / Filling factor ANOFOL Coil: Almost no space between layers No elect. insulation between layers needed Insulation layer thickness 1-6µm Filling factor 0,85-0,995 Copper Coil: Insulation layer on wire Elect. insulation between layers needed Filling factor >0,52 zimmermann@anofol.de 10

10 Mechanical Properties Coil weight Specific weight Aluminum ~ 1/3 Specific weight Copper Resistance Aluminum wire ~ 1.61* Resistance Copper wire For equal electric conductance coils: ANOFOL coils have half weight of Copper Coils zimmermann@anofol.de 11

11 Thermodynamic Properties Possible operation temperature ANOFOL Coil: Oxide melting point >2000 C Aluminum melting point 658 C ANOFOL coil continuous operation at 500 C Suitability for high temperature service Copper Coil: >180 C oxidation of copper possible >180 C silver or nickel-plated wire needed Only few insulation materials available zimmermann@anofol.de 12

12 Thermodynamic Properties Superior heat dissipation ANOFOL Coil: Heat can dissipate from the centre along aluminium strip Copper Coil: Poor thermal conductivity of insulation Air inclusions lead to heat built-up 13

13 THERMOGRAPHIC COMPARISON OF A 30KVA TRANSFORMATOR zimmermann@anofol.de 14

14 After 30 Minutes Copper Coil ANOFOL Coil 15

15 After 240 Minutes Copper Coil ANOFOL Coil 17

16 Thermodynamic Properties Lower operation temperature Coils with same electric conductance: Surface of ANOFOL coils 27% larger than copper coils Heat capacity of aluminum coils larger than copper Heat conductance and heat radiation of aluminum oxide layer larger than typical insulation layers Lower operation temperature 18

17 Usage in Special Environment High temperature environment Vacuum No out gassing of insulation layer Radioactive environment 19

18 Winding Accuracy and Filling Factor High Winding Precision Almost no gap between layers ~80µm 20

19 Resistance Calculation Accuracy 21

20 Resistance Calculation Accuracy Numerical Algorithm uses corrections: Due to milling/rolling Due to slitting Due to anodizing Due to filling factors Additional corrections 22

21 Accuracy of Coil Inductance High accuracy: Raw material Anodizing layer Coil geometry Winding High accuracy for functional parameter of Coils e.g. inductance Resolution 1/3 turn at 250 turns 23

22 Different Geometries 24

23 Different Geometries 25

24 Summary Less weight Optimal filling factor Good heat dissipation Low heat resistance High break down voltage High winding accuracy more than 40 years of experience Thank you for your attention 26