Patent EA-001173-B1 (EA)
Title: Insulated conductor for high-voltage windings and a method of manufacturing the same
Inventor: LEIJON MATS
IPC: H02K3/14
Filed: 1997-05-27
Abstract: 1. An insulated conductor (30) for high-voltage windings in electric machines, characterized in that the insulated conductor comprises one or more strands (12), an inner, first semi-conductive layer (14) surrounding the strands (12), a first insulating layer (16) surrounding the inner, first semi-conductive layer (14) and an outer, second semi-conductive layer (18) surrounding the first insulating layer (16), which second semi-conductive layer (18) is earthed at least two different poi nts along the insulated conductor, the electric contact in the second semi-conductive layer (18) being broken (20) between two consecutive earthed points, and in that at each of said breaks (20) in the second semi-conductive layer (18) a device (24, 26) is arranged to reduce amplification of the electric field strength at said breaks (20). 2 An insulated conductor (30) for high-voltage windings in rotating electric machines, characterized in that the insulated conductor comprises one or more strands (12), an inner, first semi-conductive layer (14) surrounding the strands (12), a first insulating layer (16) surrounding the inner, first semi-conductive layer (14) and an outer, second semi-conductive layer (18) surrounding the first insulating layer (16), which second semi-conductive layer (18) is earthed at least two different poi nts along the insulated conductor, the electric contact in the second semi-conductive layer (18) being broken (20) between two consecutive earthed points, and in that at each of said breaks (20) in the second semi-conductive layer (18) a device (24, 26) is arranged to reduce amplification of the electric field strength at said breaks (20). 3. An insulated conductor (30) as claimed in claim 2, characterized in that the second semi-conductive layer (18) is electrically insulated from the stator within the stator slot and that the second semi-conductive layer (18) has at least one break and one earthing point in the overhang region for each stator slot that the cable passes through. 4. An insulated conductor (30) as claimed in claim 1, 2 or 3, characterized in that the electric contact in the second semi-conductive layer (18) is broken by the second semi-conductive layer (18) having been remove d around the periphery of the insulated conductor (30) down to the first insulating layer (16) so that grooves (20) are formed flanked by the second semi-conductive layer (18). 5. An insulated conductor (30) as claimed in claim 4, characterized in that the device (24, 26) for reducing amplification of electric field strength at said break (20) comprises a second insulating layer (24) arranged over each groove (20), said layer (24) also covering a part of the second semi-conductive layer (18) on both sides of each groove (20), and in that said devices (24, 26) also comprise a third semi-conductive layer (26) arranged at the insulating layer (24), the third semi-conductive layer (26) at one end covering one edge of the second insulating layer (24) and being in electric contact with the second semi-conductive layer (18) and at its other end not cove ring the other edge of the second insulating layer (24) but extending over a part of the second semi-conductive layer (18) situated beneath the second insulating layer (24). 6. An insulated conductor (30) as claimed in claim 5, characterized in that at said groove (20) the edges of the second semi-conductive layer (18) are bevelled in such a way that the grooves (20) have least width at the first insulating layer (16). 7. An insulated conductor (30) as claimed in claim 6, characterized in that at the end covering one edge of the second insulating layer (24), the third semi-conductive layer (26) is in mechanical contact with the second semi-conductive layer (18), and in that at its other end the third semi-conductive layer (26) is not in mechanical or electrical contact with the second semi-conductive layer (18). 8. An insulated conductor (30) as claimed in claim 7, characterized in that the second insulating layer (18) consists of insulating EPDM tape. 9. An insulated conductor (30) as claimed in claim 8, characterized in that the third semi-conductive layer (26) consists of a semi-conducting rubber-based tape. 10. A electric machine comprising an insulated conductor (30) as claimed in any of claims 1-9. 11. A method of adapting an insulated conductor (30) for high-voltage windings in electric machines, said insulated conductor (30) comprising one or m ore strands (12), an inner, first semi-conductive layer (14) surrounding the strands (12), a first insulating layer (16) surrounding the inner, first semi-conductive layer (14) and an outer, second semi-conductive layer (18) surrounding the first insulating layer (16), which second semi-conductive layer (18) is earthed at least two different points along the insulated conductor (30), said method comprising the steps of: producing a break (20) in the electric contact in the second semi-conductive layer (18) between each pair of earthed points; and at each of said breaks (20) in the second semi-conductive layer (18) arranging a device (24, 26) to reduce amplification of the electric field strength at said break (20). 12. A method as claimed in claim 11, characterized in that said break (20) is produced by removing the second semi-conductive layer (18) around the periphery of the insulated conductor (30) down as far as the first insulating layer (16) so that grooves (20) are produced flanked by the second semi-conductive layer (18). 13. A method as claimed in claim 12, characterized in that the step of applying said devices (24, 26) comprises the steps of: applying a second insulating layer (24) over each groove (20) in such as manner as to cover part of the second semi-conductive layer (18) on both sides o f every groove (20); and applying a third semi-conductive layer (26) on the second insulating layer (24) in such a manner that the third semi-conductive layer (26) at one end cover s one edge of the second insulating layer (24) and is in electric contact with the second semi-conductive layer (18) and at its other end does not cover the other edge of the second insulating layer (24) but extends over a part of the second semi-conductive layer (18) situated beneath the second insulating layer (24).