Electric machine wedges and method for insertion of wedges
A stator for an electric machine includes a stator core defining an axial direction, a first end, and a second end. The stator core includes a plurality of slots formed between a plurality of teeth, wherein each of the plurality of slots extend from the first end to the second end of the stator core and define a slot opening on a radially inward portion of the stator core. A plurality of conductors are positioned in each of the slots and are connected together to form a winding arrangement for the stator. A wedge is positioned in each slot of the stator core radially inward from the plurality of conductors positioned in said slot. The wedge includes a first leg positioned on one side of the slot, a second leg positioned on an opposite side of the slot, and a bridge spanning across the slot opening.
1 . A stator for an electric machine comprising:
a stator core defining an axial direction, a first end, and a second end, the stator core including an outer diameter wall and a plurality of teeth extending radially inward from the outer diameter wall with minicaps positioned at radially inward ends of teeth and extending in a circumferential direction, wherein a plurality of slots are formed between the teeth, each of the plurality of slots extending from the first end to the second end of the stator core and defining a slot opening on a radially inward portion of the stator core between a pair of minicaps, wherein a width of each slot opening is less than a width of each slot;
a plurality of conductors positioned in each of the slots, the plurality of conductors including a radially innermost conductor defining a first side and an opposite second side of the radially innermost conductor;
a wedge positioned in each slot of the stator core radially inward from the plurality of conductors positioned in said slot, the wedge including a first leg positioned on one side of said slot, a second leg positioned on an opposite side of said slot, and a bridge connecting the first leg to the second leg, wherein the bridge spans across the slot opening and a radially inward side of the bridge faces a radially outward side of the pair of minicaps; and
a plurality of slot liners positioned in a plurality of slots, each slot liner open at the slot opening of an associated slot and including a first side on the one side of the associated slot and a second side positioned on a second side of the associated slot such that the plurality of conductors are positioned between the first side and the second side of the slot liner;
wherein the first leg of the wedge is positioned between and engages the first side of the slot liner and the first side of the radially innermost conductor in the associated slot, and wherein the second leg of the wedge is positioned between and engages the second side of the slot liner and the second side of the radially innermost conductor in the associated slot.
2 . The stator of claim 1 wherein the wedge is friction fit in the slot with the first leg wedged on one side of said slot and the second leg wedged on the opposite side of said slot.
3 . The stator of claim 2 wherein the plurality of conductors in each slot are arranged in a single-file line extending in a radial direction.
4 . The stator of claim 3 wherein the wedge is flexible and comprised of an electrically insulative material.
5 . The stator of claim 2 wherein the first leg of the wedge is compressed and is thinner than the bridge of the wedge.
6 . The stator of claim 1 wherein each slot has a larger width at a position immediately radially outward from the pair of minicaps than at a radial midpoint of the slot.
7 . The stator of claim 6 wherein each tooth of the plurality of teeth is tapered circumferentially inward at a position radially outward from the minicaps.
8 . The stator of claim 1 wherein the first leg of the wedge is at least 2 mm long and at least as long as a radial thickness of the innermost conductor in the associated slot.
9 . The stator of claim 8 wherein the first leg of the wedge contacts the radially innermost conductor and a radially inner penultimate conductor without contacting any additional conductors in the associated slot.
10 . The stator of claim 1 wherein the wedge is at least partially comprised of a plastic or thermoplastic with a high column strength.
11 . The stator of claim 1 wherein the wedge is longer than the slot liner in the axial direction in the associated slot.
12 . The stator of claim 1 wherein the bridge of the wedge is not in contact with the pair of minicaps in the associated slot.
13 . An electric machine comprising:
a rotor; and
a stator separated from the rotor by an airgap and defining an axial direction, the stator comprising:
a stator core including a plurality of slots, each slot including an opening;
a winding arrangement formed by conductors extending through the slots of the stator core;
a plurality of slot liners positioned in the plurality of slots, each slot liner including a first side positioned on one side of an associated slot and a second side positioned on a second side of the associated slot such that the conductors in the associated slot are positioned between the first side and the second side of the slot liner; and
a plurality of wedges positioned in the slots of the stator core, wherein at least a portion of each wedge is positioned radially outward from an opening of the associated slot, wherein each wedge includes a first leg positioned between the first side of the slot liner and a radially innermost conductor in the associated slot, a second leg positioned between the second side of the slot liner and the radially innermost conductor in the associated slot, and a bridge extending between the first leg and the second leg, wherein the bridge blocks an opening to the associated slot, and wherein each wedge is friction fit in the slot with the first leg wedged between the first side of the slot liner and a first side of the radially innermost conductor on one side of said slot and the second leg wedged between the second side of the slot liner and a second side of the radially innermost conductor on an opposite side of said slot.
14 . The electric machine of claim 13 wherein each of the plurality of slots is a semi-closed slot defined by minicaps on a radially inward side of the slot, wherein each wedge is positioned completely radially outward from the minicaps on the radially inward side of the slot, wherein a width of each conductor is less than a width of the associated slot, and wherein a width of the bridge is greater than the width of the opening to the associated slot.
15 . The electric machine of claim 14 wherein the first leg of each wedge is longer than a radial thickness of each conductor in the associated slot.
16 . A method of making a stator for an electric machine comprising:
inserting conductors into slots of a stator core, the stator core defining an axial direction, a circumferential direction, and a radial direction, the stator core including an outer diameter wall and teeth extending radially inward from the outer diameter wall with minicaps positioned at radially inward ends of the teeth and extending in the circumferential direction, wherein the slots are formed between the teeth, each of the slots defining a slot opening on a radially inward portion of the stator core between a pair of the minicaps, wherein a width of each slot opening is less than a width of each slot radially outward from said slot opening, wherein the conductors are inserted into the slots of the stator core through the slot openings;
inserting slot liners into the slots such that, for each slot liner, a first side of said slot liner is positioned on one side of an associated slot, a second side of said slot liner is positioned on an opposite side of the associated slot, and the conductors in the associated slot are positioned between the first side and the second side of the slot liner; and
inserting wedges through the slot openings in a radial direction and into the slots such that in each slot:
a first leg of a wedge is positioned between the one side of the slot liner and a radially innermost conductor in the slot,
a second leg of the wedge is positioned between the opposite side of the slot liner and the radially innermost conductor in the slot,
a bridge of the wedge blocks the slot opening, and
the wedge is friction fit in the slot with the first leg wedged between the first side of the slot liner and a first side of the radially innermost conductor on the one side of said slot and the second leg wedged between the second side of the slot liner and the second side of the radially innermost conductor on the opposite side of said slot.
17 . The method of claim 16 further comprising positioning a guide fixture adjacent to one of the slots prior to inserting the wedge into said one of the slots.
18 . The method of claim 17 wherein the guide fixture comprises a through-hole including a first opening on a radially inward side of the guide fixture that is larger than a second opening on a radially outward side of the guide fixture.
19 . The method of claim 18 wherein the conductors are inserted through the slot openings in the radial direction, and wherein a width of the second opening is less than a width of each slot opening.
20 . The method of claim 19 wherein a width of the through-hole is gradually tapered between the first opening and the second opening.
21 . The method of claim 20 further comprising inserting the wedge in the through-hole of the guide fixture with a bridge of the wedge positioned closer to the first opening than the second opening, and the first leg and the second leg of the wedge extending from the bridge towards the second opening.
22 . The method of claim 21 wherein inserting wedges through the slot openings and into the slots includes inserting a pusher tool through the through-hole in the guide fixture such that the wedge in the through-hole is forced past the second opening, past the slot opening, and into the slot.