Influence of aluminium oxidation on insulation properties of oxide coating

The article presents the influence of aluminium oxidation parameters on the insulating properties of oxide coatings on aluminium strips of electrical windings. The effect of H ₂ SO ₄ electrolyte concentration, its temperature and anode current density on the value of unit breakdown voltage was determined. A significant influence of the contact surface area of the measuring electrode with the coating on the breakdown voltage was found. The error of breakdown voltage measurement does not exceed 5% if the contact surface area of the electrode is a minimum of 10 cm ² . Constant and varying components of the breakdown voltage were distinguished. The constant component is up to 55% of the value and depends mainly on the thickness of the coating. The varying component depends on the surface topography of the oxide, mainly on the number of roughness peaks per unit area.