Lightweight and efficient electrical machine and method of manufacture
A lightweight and efficient electrical machine element including a method of manufacture providing a stator winding for an electric machine which has a large portion of its volume containing electrically conductive strands and a small portion of its volume containing of an encapsulant material. The stator winding includes winding of a first phase by shaping a portion of a bundle of conductive strands into an overlapping, multi-layer arrangement. Winding of successive phases occurs with further bundles of conductor strands around the preceding phases constructed into similar overlapping, multi-layer arrangements. The multiple phases are impregnated with the encapsulant material using dies to press the bundles into a desired form while expelling excess encapsulant prior to the curing of the encapsulant material. The encapsulated winding is removed from the dies after the encapsulant has cured. The encapsulant coating on the strands may be activated using either heat or solvent. The stator winding may be pressed into a form which has cooling channels which increase the surface area, thus enhancing convective cooling, heat dissipation, and the electrical machine's efficiency.
1. A single-layer, poly-phase Litz wire winding for a coreless stator of an axial flux electrical machine, the winding comprising:
conductors having a single conductor in each phase and slot position, the conductors forming end turns in an uncompressed state within an end turn region of the winding, the conductors selected from insulated strands that are formed into a rectangular woven braid or insulated strands that are formed into a rectangular bundle and each having a rectangular conductor cross section with an aspect of 1.5:1 or more;
a polymer resin encapsulating the conductors; and
wherein each single conductor in each phase traverses around the winding only once without crossing over or touching itself such that turn-to-turn short circuits within a phase are precluded.
2. The single-layer winding of claim 1 including a thermally conductive ring affixed to an edge of the winding in thermal contact with the end turns, and the polymer resin fills voids and gaps between the end turns and the ring while providing a thermal path from the end turns to the ring.
3. The single-layer winding of claim 1 having a thermally conductive fin placed between at least two of the end turns.
4. The single-layer winding of claim 1 having a thermally conductive core extending through the end turn region of the winding in at least two locations, and a thermally conductive fin extending from the core and between at least two of the end turns.
5. The single-layer winding of claim 1 having a thermally conductive coolant tube passing through the end turn region of the winding in at least two locations, the tube including at least two terminals for introducing coolant into the tube and removing coolant from the tube, and the encapsulant fills voids and gaps between the end turns and the tube while providing a thermal path from the end turns to outer surface of the tube.
6. A single-layer, poly-phase Litz wire winding for a coreless stator of an axial flux electrical machine, the winding comprising:
conductors having a single conductor in each phase and slot position, the conductors forming end turns in an uncompressed state within an end turn region of the winding, the conductors selected from insulated strands that are formed into a rectangular woven braid or insulated strands that are formed into a rectangular bundle and each having a rectangular conductor cross section with an aspect of 1.5:1 or more;
a polymer resin encapsulating the conductors; and
wherein the conductors are twisted such that in the end turn region of the winding each conductor has a cross sectional dimension in a direction of its instantaneous center of curvature vector that is smaller than a cross section dimension perpendicular to the instantaneous center of curvature vector, and the conductors include phase leg width in a circumferential direction that is substantially less than a dimension of the phase leg in an axial direction, and each conductor traverses around the winding only once without crossing over or touching itself such that turn-to-turn short circuits within a phase are precluded.
7. The single-layer winding of claim 6 including a thermally conductive ring affixed to an edge of the winding in thermal contact with the end turns, and the polymer resin fills voids and gaps between the end turns and the ring while providing a thermal path from the end turns to the ring.
8. The single-layer winding of claim 6 having a thermally conductive fin placed between at least two of the end turns.
9. The single-layer winding of claim 6 having a thermally conductive core extending through the end turn region of the winding in at least two locations, and a thermally conductive fin extending from the core and between at least two of the end turns.
10. The single-layer winding of claim 6 having a thermally conductive coolant tube passing through the end turn region of the winding in at least two locations, the tube including at least two terminals for introducing coolant into the tube and removing coolant from the tube, and the encapsulant fills voids and gaps between the end turns and the tube while providing a thermal path from the end turns to outer surface of the tube.