Patent EA-001098-B1 (EA)
Title: A device in the stator of a rotating electric machine
Inventor: LEIJON MATS
IPC: H01F27/28
Filed: 1997-05-27
Abstract: 1. A device for increasing the mechanical rigidity and natural frequency of the stator in a rotating electric machine, which stator is provided with teeth (10) between the slots (8) receiving the winding, the free ends of said teeth being located in the air gap (7) between stator and rotor, characterized in that the winding comprises a high-voltage cable (1) and that a spacer (11) to increase rigidity is arranged in each space between the free ends of adjacent stator teeth (10) to tangentially fix said ends. 2. A device as claimed in claim 1 characterized in that the spacer comprises a wedge (11). 3. A device as claimed in claim 2, characterized in that the wedge surfaces converge outwardly towards the ends of the stator teeth (10) connected to each other, the wedge (11) being arranged to be subjected to a radial, outwardly directed force during assembly. 4. A device as claimed in claim 2 characterized in that the wedge surfaces diverge outwardly towards the ends of the stator teeth (10) connected to each other, an expansion means (14) being arranged between the wedge (11) and the cable (1) of the winding situated nearest to the slot (8) and secured in a seat in the slot (8). 5. A device as claimed in claim 4 characterized in that the expansion means consists of a tube (14) which is filled with a liquid compound, such as epoxy plastic, which is curable under pressure. 6. A device as claimed in any of claims 1-5, characterized by adhesive joints between the spacers (11) and stator teeth (10). 7. A device as claimed in claim 1 or claim 2 characterized in that the outer stator frame (17) is provided with a spring member (16) for tangential clamping of the outer part of the stator core (15) and to produce a tangential thrust force in the surfaces of the spacers at the free ends of the stator teeth (10). 8. A device as claimed in any of claims 1-7 characterized in that the spacers (11) which extend the entire length of the stator are designed as tie rods to pre-stress the stator core (15). 9. A device as claimed in claim 8 characterized in that a force-transmitting device (18) is arranged between the spacers (11) and the outer periphery of the stator and arranged to convert tensile stress in the spacers (11 ) to compressive stress in the stator core (15). 10. A device as claimed in claim 9 characterized in that the spacers (11) are connected together at their ends by means of transverse pieces (19) and in that the force-transmitting device consists of pressure fingers (18) extending radially on each side of the stator core (15) immediately opposite the stator teeth (10) the inner ends of said fingers protruding inside the transvers e pieces (19) and the outer ends being pressed against the core (15) by means of a clamping device (22, 23) on the stator frame (17). 11. A device as claimed in claim 9 characterized in that the ends of the spacers (11) are provided with screw threading (25) for cooperation with a nut (24) to transfer compressive force via a plate (26) to the stator teeth (10). 12. A rotating electric machine characterized by a device as claimed in any of claims 1-11 to increase the natural frequency of the stator. 13. A rotating electric machine according to claim 12 characterized in that the winding comprises at least one current-carrying conductor (2), a first layer (3) having semi-conducting properties provided around said conductor (2), a solid insulating layer (4) provided around said first layer (3), and a second layer (5) having semi-conducting properties provided around said insulating layer (4). 14. A rotating electric machine according to claim 13, characterized in that the potential of said first layer (3) is substantially equal to the potential of the conductor (2). 15. A rotating electric machine according to claim 13 or 14, characterized in that said second layer (5) is arranged to constitute substantially an equipotential surface surrounding said conductor (2). 16. A rotating electric machine according to claim 15, characterized in that said second layer (5) is connected to a predetermined potential. 17. A rotating electric machine according to claim 16, characterized in that said predetermined potential is ground potential. 18. A rotating electric machine according to any one of claims 13-17, characterized in that at least two adjacent layers have substantially equal thermal expansion coefficients. 19. A rotating electric machine according to any one of claims 13-18, characterized in that said current-carrying conductor (2) comprises a number of strands, only a minority of said strands being non-isolated from each other. 20. A rotating electric machine according to any one of claims 13-19, characterized in that each of said three layers is fixed connected to adjacent layer along substantially the whole connecting surface. 21. A rotating electric machine according to any one of claims 13-20, characterized in that said cable (1) also comprises a metal shield and a sheath.