Nested three phase bus bar unit
Certain aspects relate to a bus bar unit for providing three phases of electric current to the windings of the stator of an electric machine while structured to have a compact footprint for fitting within the enclosure of the electric machine. Each winding can have a phase lead end and a neutral end extending above one face of the stator. The bus bar unit can include three phase lead bus bars and a neutral bus bar each having a planar branch with legs extending from the planar branch, each leg having a slot at an end thereof for electrically coupling with either the phase lead or the neutral end of one or more of the windings. The planar branches can be stacked such that they overlap from a top-down perspective but are spaced apart from a side perspective.
1. A three-phase electric machine comprising:
a stator having a plurality of teeth separated by a plurality of slots;
a plurality of windings provided in a winding pattern in the plurality of slots, each of the plurality of windings having a phase lead end and a neutral end extending beyond an end face of the stator; and
a bus bar unit positioned adjacent to the end face of the stator to receive the phase lead end and the neutral end of each of the plurality of windings, the bus bar unit comprising:
first, second, and third phase lead bus bars, wherein each of the first, second, and third phase lead bus bars comprises:
a planar branch,
at least a first leg extending from the planar branch, the first leg having a first phase lead slot sized to receive the phase lead end of at least one of the plurality of windings, and
a connection terminal extending from the planar branch for receiving one of three phases of electric current; and
an enclosure enclosing the stator, the plurality of windings, and the branches and legs of the bus bar unit;
wherein the winding pattern includes a plurality of layers in each of the plurality of slots with an inner layer positioned adjacent an inner diameter of the stator and an outer layer positioned adjacent a backiron of the stator;
the phase lead end of each a first subset of the plurality of windings extends above the end face of the stator from the inner layer;
the neutral end of each of the first subset of the plurality of windings extends above the end face of the stator from the outer layer;
the phase lead end of each a second subset of the plurality of windings extends above the end face of the stator from the outer layer; and
the neutral end of each of the second subset of the plurality of windings extends above the end face of the stator from the inner layer.
2. The three-phase electric machine of claim 1 , further comprising a neutral bus bar;
wherein:
the neutral bus bar comprises a first set of at least three legs and a second set of at least three legs, each of the first set of legs having a first neutral slot and each of the second set of legs having a second neutral slot;
each of the first, second, and third phase led bus bars further comprises a second leg, each of the second legs having a second phase lead slot;
the first phase lead slot of each of the first, second, and third phase lead bus bars is positioned to receive the phase lead end of at least one of the first subset of the plurality of windings;
the first neutral slot of each of the first set of legs of the neutral bus bar is positioned to receive the neutral end of at least one of the second subset of the plurality of windings;
the second phase lead slot of each of the first, second, and third phase lead bus bars is positioned to receive the phase lead end of at least one of the second subset of the plurality of windings; and
the second neutral slot of each of the second set of legs of the neutral bus bar is positioned to receive the neutral end of at least one of the first subset of the plurality of windings.
3. A three-phase electric machine comprising:
a stator having a plurality of teeth separated by a plurality of slots;
a plurality of windings provided in a winding pattern in the plurality of slots, each of the plurality of windings having a phase lead end and a neutral end extending beyond an end face of the stator; and
a bus bar unit positioned adjacent to the end face of the stator to receive the phase lead end and the neutral end of each of the plurality of windings, the bus bar unit comprising first, second, and third phase lead bus bars and a neutral bus bar;
wherein each of the first, second, and third phase lead bus bars comprises:
a planar branch,
a first leg extending from the first planar branch, the first leg having a first phase lead slot sized to receive the phase lead end of at least one of the plurality of windings,
a second leg extending from the planar branch, the second leg having a second phase lead slot sized to receive the phase lead end of at least one of the plurality of windings, and
a connection terminal extending from the first planar branch for receiving one of three phases of electric current;
wherein the neutral bus bar comprises:
a first planar branch of the neutral bus bar and a first set of at least three legs extending from the first planar branch of the neutral bus bar, each of the first set of legs having a first neutral slot sized to receive the neutral end of at least one of the plurality of windings, and
a second planar branch of the neutral bus bar and a second set of at least three legs extending from the second planar branch of the neutral bus bar, each of the second set of legs having a second neutral slot sized to receive the neutral end of at least one of the plurality of windings;
wherein the first phase lead slots of each of the first, second, and third phase lead bus bars and the first neutral slots of the neutral bus bar are positioned along an inner circumference of the stator, wherein the second phase lead slots of each of the first, second, and third phase lead bus bars and the second neutral slots of the neutral bus bar are positioned along an outer circumference of the stator, wherein the inner and outer circumferences are concentric with one another with the inner circumference having a smaller diameter than the outer circumference; and
an enclosure enclosing the stator, the plurality of windings, and the branches and legs of the bus bar unit.
4. The three-phase electric machine of claim 3 , wherein the first, second, and third phase lead bus bars are positioned in a stack such that:
from a top-down perspective orthogonal to the end face of the stator, the planar branches of each of the first, second, and third phase lead bus bars overlap at least partially with one another; and
from a side perspective orthogonal to the top-down perspective, the planar branches of each of the first, second, and third phase lead bus bars are spaced apart from one another.
5. The three-phase electric machine of claim 3 , wherein each of the plurality of windings is a continuous winding comprising a plurality of leg portions each positioned in one of the plurality of slots of the stator and a plurality of crowns connecting successive leg portions of the plurality of leg portions, the crowns extending above the end face of the stator.
6. The three-phase electric machine of claim 5 , wherein the bus bar unit is positioned between a peak of each of the plurality of crowns and an inner surface of the enclosure.
7. The three-phase electric machine of claim 3 , wherein the connection terminal of each of the first, second, and third phase lead bus bars is mechanically coupled to the enclosure.
8. The three-phase electric machine of claim 3 , wherein the phase lead ends of a first subset of the plurality of windings are electrically coupled to the respective first phase lead slots to receive respective phases of the three phases of electric current, and wherein the phase lead ends of a second subset of the plurality of windings are electrically coupled to the respective second phase lead slots to receive respective phases of the three phases of electric current.
9. The three-phase electric machine of claim 8 , wherein the first and second neutral slots of neutral bus bar electrically couple the neutral ends of the plurality of windings with one another.