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, extending between the first side and the second side;
a coil, formed by coil elements comprising looped coil elements and extended coil elements, the coil elements protruding through the stator core, wherein:
each of the looped coil elements protrudes through two of the stator slots and is directly connected to two other corresponding ones of the coil elements at the first side of the stator core;
at least one of the looped coil elements comprises loop extensions and an end loop, interconnecting the loop extensions and extending from the second side of the coil elements, the end loop having no radial offset relative to the loop extensions,
each of the coil elements has a rectangular cross-section; and
a lead assembly, comprising three phase busbars, wherein:
each of the three phase busbars is electrically coupled to at least one of the coil elements at the second side of the stator core, and
each of the three phase busbars comprises an external terminal for connecting the fractional slot electric motor to an external power supply.
2. The fractional slot electric motor of claim 1 , wherein the lead assembly further comprises two neutral busbars, each electrically coupled to at least one of the coil elements at the second side of the stator core.
3. The fractional slot electric motor of claim 2 , wherein the two neutral busbars and the three phase busbars are stacked within the lead assembly and are electrically isolated from each other.
4. The fractional slot electric motor of claim 3 , wherein the lead assembly comprises a busbar insulator, molded over each of the two neutral busbars and the three phase busbars and mechanically supporting the two neutral busbars and the three phase busbars with respect to each other.
5. The fractional slot electric motor of claim 4 , wherein each of the three phase busbars comprises one or more phase terminals, protruding from the busbar insulator and electrically coupled to one or more of the coil elements.
6. The fractional slot electric motor of claim 4 , wherein each of the two neutral busbars comprises one or more neutral terminals, protruding from the busbar insulator and electrically coupled to one or more of the coil elements.
7. The fractional slot electric motor of claim 4 , wherein the lead assembly further comprises a busbar thermocouple, supported on the busbar insulator and thermally coupled to one of the three phase busbars, partially protruding through the busbar insulator.
8. The fractional slot electric motor of claim 1 , wherein each of the three phase busbars further comprises a hoop such that the external terminal is flexibly connected to the hoop.
9. The fractional slot electric motor of claim 8 , wherein:
each of the three phase busbars further comprises a neck, flexibly connected to the hoop to the external terminal, and
the neck is formed by a plurality of metal strips.
10. The fractional slot electric motor of claim 8 , wherein the three phase busbars are stacked in the lead assembly.
11. The fractional slot electric motor of claim 1 , wherein the extended coil elements are connected at both the first side and the second side of the stator core.
12. The fractional slot electric motor of claim 11 , wherein:
each of the looped coil elements comprises an end loop and two loop extensions, interconnected by the end loop and each terminating with loop extension end,
the loop extension end of each of the two loop extensions extends from the stator core at the first side and connected to one of the coil elements, and
the end loop extends from the stator core at the second side between two different ones of the stator slots.
13. The fractional slot electric motor of claim 12 , wherein the end loop of each of the looped coil elements is positioned between the second side of the stator core and the lead assembly.
14. The fractional slot electric motor of claim 12 , wherein the two loop extensions of one of the of the looped coil elements extend through the two different ones of the stator slots at same positions.
15. The fractional slot electric motor of claim 12 , wherein the two loop extensions of one of the looped coil elements extend through the two different ones of the stator slots at different positions.
16. The fractional slot electric motor of claim 11 , wherein:
each of the extended coil elements comprises a first end, an extension, and a second end,
the extension protrudes through the stator core between the first side and the second side and interconnects the first end and the second end,
the first end extends from the stator core at the first side and is connected to one of the coil elements, and
the second end extends from the stator core at the second side and is connected to one of the coil elements or the lead assembly.
17. The fractional slot electric motor of claim 16 , wherein the second end of each of the extended coil elements is at least partially protrudes past the lead assembly.
18. The fractional slot electric motor of claim 15 , wherein the second end is radially offset relative to the extension.
19. The fractional slot electric motor of claim 1 , wherein the coil elements are arranged into a three-phase two-parallel configuration.
20. The fractional slot electric motor of claim 1 , wherein the rectangular cross-sectional 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.