A high voltage stator bar includes a substantially quadrangular conductive element made of a plurality of interwoven strands, and an electric insulation applied around the conductive element. The permittivity at the corners of the electric insulation decreases by less than 60% from an inner insulation zone facing the conductive element towards an outer insulation zone.
1. A stator bar comprising:
a substantially quadrangular conductive element made of a plurality of interwoven strands; and
an electric insulation applied around the conductive element and including a plurality of corners corresponding to corners of the conductive element, the electric insulation including an inner insulation zone facing the conductive element, and an outer insulation zone surrounding the inner insulation zone, a radius of at least one of the corners being 1.5-2.5 millimeters,
wherein permittivity at the corners of the electric insulation decreases by 35-45% from the inner insulation zone facing the conductive element towards the outer insulation zone,
wherein the insulation comprises a mica tape impregnated with a resin, and
wherein the mica tape at the inner insulation zone has a lower resin content than the mica tape at the outer insulation zone.
2. The stator bar as claimed in claim 1 , wherein the mica tape includes a plurality of mica tapes having different compressibility to achieve different resin content.
3. The stator bar as claimed in claim 1 , wherein the mica tape includes strips of mica tape that parallel to the corners of the conductive element to achieve a different resin content.
4. The stator bar as claimed in claim 1 , wherein the permittivity defines at least a step.
5. The stator bar as claimed in claim 1 , wherein the permittivity decreases at least partly continuously in a radial direction.
6. A generator comprising the stator bar as claimed in claim 1 ,
wherein the generator has more than 100 MW output power and a nominal voltage greater than 10 kVAC.
7. A stator bar comprising:
a substantially quadrangular conductive element made of a plurality of interwoven strands; and
an electric insulation applied around the conductive element and including a plurality of corners corresponding to corners of the conductive element, the electric insulation including an inner insulation zone facing the conductive element, and an outer insulation zone surrounding the inner insulation zone, a radius of at least one of the corners being 1.5-2.5 millimeters,
wherein permittivity at the corners of the electric insulation decreases by 35-45% from the inner insulation zone facing the conductive element towards the outer insulation zone,
wherein the insulation comprises a mica tape impregnated with a resin,
wherein the mica tape is wrapped with different wrapping tension to achieve different resin content, and
wherein the wrapping tension is higher at the beginning of the wrapping and lower at the end of wrapping.
8. The stator bar as claimed in claim 7 , wherein the permittivity defines at least a step.
9. The stator bar as claimed in claim 7 , wherein the permittivity decreases at least partly continuously in a radial direction.