Fractional slot electric motors with coil elements having rectangular cross-sections
Described herein are fractional slot electric motors with compact crowns. A motor comprises multiple coil elements protruding through a stator core and forming electrical connections with each other and/or with a lead assembly. The lead assembly comprises phase busbars connected to selected coil elements and comprising terminals for connecting to an external power supply. The lead assembly also comprises neutral busbars, with no external connections and internally connected to other coil elements. Each coil element has a rectangular cross-sectional profile to maximize the slot-fill-ratio of the motor. Each coil element is electrically coupled to two other components. For example, each looped coil element is coupled to two other coil elements at a stator side, opposite the lead assembly. Each extended coil element is coupled to another coil element at that same side and coupled to another coil element or a busbar at the lead assembly side.
1. A fractional slot electric motor comprising:
a stator core comprising a first side, a second side, and stator slots, wherein the stator slots extend between the first side and the second side; and
a coil comprising a plurality of coil elements, the coil elements comprising a looped coil element, wherein:
the looped coil element comprises (i) loop extensions and (ii) an end loop interconnecting the loop extensions and extending from the second side of the stator core,
the end loop has no radial offset relative to the loop extensions, and
the loop extensions protrude through loop-extension slots of the stator slots and are directly connected, at the first side of the stator core, to two others of the coil elements.
2. The fractional slot electric motor of claim 1 , wherein the loop extensions of the looped coil element protrude through the loop-extension slots that are spaced apart from each other by five other slots of the stator slots.
3. The fractional slot electric motor of claim 1 , wherein the loop extensions of the looped coil element protrude through the loop-extension slots that are spaced at radially innermost positions within the loop-extension slots.
4. The fractional slot electric motor of claim 3 , wherein each of the stator slots comprises at least four positions, each position having a different radial offset.
5. The fractional slot electric motor of claim 1 , wherein the end loop of the looped coil element comprises a return loop circumferentially extending past the loop-extension slots through which the loop extensions of the looped coil element protrude.
6. The fractional slot electric motor of claim 1 , wherein the looped coil element is one of at least six looped coil elements, the looped coil elements comprising respective end loops having no radial offset relative to respective loop extensions.
7. The fractional slot electric motor of claim 1 , wherein the coil elements further comprise an extended coil element protruding through an extended-coil slot of the stator slots.
8. The fractional slot electric motor of claim 7 , wherein the extended-coil slot of the stator slots is adjacent to one of the loop-extension slots.
9. The fractional slot electric motor of claim 7 , wherein at least a portion of the extended coil element extends from the second side of the stator core and conforms to the end loop of the looped coil element.
10. The fractional slot electric motor of claim 7 , further comprising a lead assembly, the lead assembly comprising three-phase busbars the lead assembly positioned adjacent to the second side of the stator core, wherein the extended coil element is connected to one of the three-phase busbars.
11. The fractional slot electric motor of claim 10 , wherein the end loop of the looped coil element is positioned between the second side of the stator core and the lead assembly.
12. The fractional slot electric motor of claim 7 , wherein:
the extended coil element comprises a portion protruding from the extended-coil slot at the second side of the stator core and terminating with an end, and
the end of the extended coil element is positioned over one of the stator slots that is spaced apart from the extended-coil slot by three other slots of the stator slots.
13. The fractional slot electric motor of claim 12 , wherein the portion of the extended coil element at least in part extends radially away from a center of the stator core relative to the extended-coil slot.
14. The fractional slot electric motor of claim 13 , wherein the end of the extended coil element is positioned radially closer to the center of the stator core than the extended-coil slot.
15. The fractional slot electric motor of claim 1 , wherein the coil elements are arranged into a three-phase, two-parallel configuration.
16. The fractional slot electric motor of claim 1 , wherein each of the coil elements has a rectangular cross-section.
17. The fractional slot electric motor of claim 16 , wherein the rectangular cross-section of each of the coil elements has a thickness of between 3.0 millimeters and 4.0 millimeters and a width of between 2.5 millimeters and 3.5 millimeters.
18. A looped coil element of a coil of a fractional slot electric motor comprising a stator core with stator slots, the looped coil element comprising:
loop extensions configured to protrude through loop-extension slots of the stator slots and to directly connect to two other coil elements of the coil; and
an end loop interconnecting the loop extensions and configured to extend from the stator slots with no radial offset relative to the loop extensions.
19. The looped coil element of claim 18 , wherein the loop extensions are spaced apart such that the loop-extension slots, through which the loop extensions are configured to protrude, are spaced apart from each other by five other slots of the stator slots.
20. The looped coil element of claim 18 , wherein the end loop comprises a return loop configured to radially extend past the loop-extension slots through which the loop extensions are configured to protrude.