Permanent magnet synchronous machine rotor geometries with a maximized torque-speed density

Abstract

Permanent magnet synchronous motors (PMSM) are normally used due to their high efficiency. These motors can be used for marine electrification, but they will not run with maximum efficiency. Many of them are not compliant with high power / high torque densities (above 5kW / kg) and are usually optimized for automotive industry. Electric motors used for marine and other propeller-based vehicles require a different optimization approach as the motor design needs to accommodate the vibration, noise, and heat associated with higher power density. To reduce the effect of these parameters and to optimize the motor for propeller-based vehicles, the electric motor geometry is specially designed in described in the present disclosure.

Description

[0001] PERMANENT MAGNET SYNCHRONOUS MACHINE ROTOR GEOMETRIES WITH A MAXIMIZED TORQUE-SPEED DENSITY

[0002] PRIORITY

[0003] The present application is related to, and claims the priority benefit of, U.S. provisional patent application serial no. 63 / 548,412, filed on November 14, 2023, the contents of which are incorporated herein directly and by reference in their entirety.

[0004] BACKGROUND

[0005] With the rapid advancement of the electric mobility field, various motor designs and technologies are being introduced. The Permanent Magnet Synchronous Machines (PMSMs) are normally used due to their high efficiency and power density compared to other electric motors such as Induction Machines (IMs). Similarly, to automotive electric mobility, these motors can be used as well for marine electrification. PMSMs usually have a high power density when compared to more traditional technologies, however pushing more of the power density has significant advantages, such as more compact design, weight savings, and better use of the materials.

[0006] Usually, these PMSMs are controlled with a Variable Fed Drive (VFD). Standard PMSMs are not compliant with power densities above 5kW / kg and are as well optimized for automotive industry. The automotive industry, for example, looks for a Constant Power Speed Ratio (CPSR) as Internal Combustion Engines (ICEs) with a gearbox have a constant power profile. However, propeller-based vehicles (like marine watercrafts) have a special load characteristic which allows a different optimization approach as resistive load is different than the automotive industry. The reasons are that it requires a very high gravimetric power density allowing to achieve a high torque and high speed of the motor. To achieve these characteristics, the motor must be solid enough to withstand high rotational speed and high temperatures without compromising the power density. Moreover, to guarantee high levels of quality in the application, low Noise Vibration and Harshness (NVH) is required to handle the high level of power density and speed. BRIEF SUMMARY

[0007] The present disclosure includes disclosure of an electric motor geometry optimized for high power density propeller-based applications consisting of a stator and a rotor. The rotor is characterized as a multi pole pairs rotor, with a magnet thickness ranging between 4- 15 mm, a rotor bridge between 1.5-3.5mm, a flux return path 305 between 2-4 mm, and a magnet post between 1.5-3.5 mm.

[0008] The present disclosure includes disclosure of a radial field electric motor geometry optimized for high power density propeller-based applications consisting of a stator and a rotor, wherein the rotor has any number of pole pairs with any pole angle, a magnet thickness ranging between 4-15 mm, a rotor bridge between 1.5 -3.5mm, a flux return path between 2-4 mm, and a magnet post between 1.5 -3.5 mm.

[0009] The present disclosure includes disclosure of a radial field electric motor optimized for propeller-based applications comprising a stator and a rotor, whereby a geometry of the rotor has multiple poles with a pole angle at or between 36° and 90°.

[0010] The present disclosure includes disclosure of a radial field electric motor, wherein the pole angle is 90°.

[0011] The present disclosure includes disclosure of a radial field electric motor, wherein the pole angle is 60°.

[0012] The present disclosure includes disclosure of a radial field electric motor, wherein the pole angle is 45°.

[0013] The present disclosure includes disclosure of a radial field electric motor, wherein the pole angle is 36°.

[0014] The present disclosure includes disclosure of a radial field electric motor, wherein the motor has a magnet aspect ratio (MAR) in a range of at or about 45-70%. The present disclosure includes disclosure of a radial field electric motor, wherein the rotor comprises magnets having a thickness ranging between at or about 4-15 mm.

[0015] The present disclosure includes disclosure of a radial field electric motor, having a good magnet power in a given volume considering a magnet manufacturing process.

[0016] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor comprises a rotor bridge ranging between at or about 1.0-3.5 mm to avoid flux leakage.

[0017] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor bridge is large enough to handle a mechanical robustness of the motor.

[0018] The present disclosure includes disclosure of a radial field electric motor, wherein a flux return path of the motor is ranging between at or about 1-5 mm.

[0019] The present disclosure includes disclosure of a radial field electric motor, wherein the flux return path has an optimum value between a good reluctance torque and magnetic torque.

[0020] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor comprises a magnet post ranging between at or about 1-5 mm.

[0021] The present disclosure includes disclosure of a radial field electric motor, wherein the magnet post is small enough to reduce or avoid flux leakage but large enough to maintain a mechanical robustness of the rotor.

[0022] The present disclosure includes disclosure of a radial field electric motor, further defining slots cutout from metal of the rotor to reduce weight of the motor.

[0023] The present disclosure includes disclosure of a radial field electric motor, wherein the slots also stream a magnetic field towards the stator without damaging flux lines. The present disclosure includes disclosure of a radial field electric motor, wherein the slots cutout from the metal of the rotor are formed in any shape and size but are symmetrical and concentric around a d-axis of the rotor.

[0024] The present disclosure includes disclosure of a radial field electric motor, wherein the slots cutout from the metal of the rotor are one or more curved linear slots with a width ranging between at or about 0.5-5 mm.

[0025] The present disclosure includes disclosure of a radial field electric motor, wherein the slots cutout from the metal of the rotor are one or more quadrilateral slots with rounded angles having any length and a width ranging between at or about 0.5-5 mm.

[0026] The present disclosure includes disclosure of a radial field electric motor, wherein the motor rotor may define slots around a shaft area.

[0027] The present disclosure includes disclosure of a radial field electric motor, wherein the slots help maintain a structural integrity of the rotor.

[0028] The present disclosure includes disclosure of a radial field electric motor, wherein the slots allow for better thermal management, supporting higher operating speeds by acting like a spring to minimize structural deformation.

[0029] The present disclosure includes disclosure of a radial field electric motor, wherein the motor rotor may include a protrusion on a same side as the slots to maintain the structural integrity of rotor.

[0030] The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor may have different shapes acting like a spring to minimize structural deformation.

[0031] The present disclosure includes disclosure of a radial field electric motor, wherein a length (dimension a) between the protrusion and a center of the motor ranges from 10.53 mm to 63.2 mm, and a length (dimension b) ranges from 10.4 mm to 63mm. The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor have a dimension (dimension c) ranging from 10.4 degrees to 63 degrees.

[0032] The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor have a length (dimension d) ranging from 4 mm to 25 mm.

[0033] The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor have a length (dimension e) ranging from 1 mm to 6 mm.

[0034] The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor have a length (dimension f) ranging from 0.5 mm to 3 mm.

[0035] The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor have a length (dimension g) ranging from 0. 125 mm to 0.75 mm.

[0036] The present disclosure includes disclosure of a radial field electric motor, wherein the slots in the rotor have a length (dimension h) ranging from 0.2 mm to 1.32 mm.

[0037] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor comprises magnets having a thickness ranging between at or about 4-15 mm.

[0038] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor comprises a rotor bridge ranging between at or about 1.0-3.5 mm.

[0039] The present disclosure includes disclosure of a radial field electric motor, wherein a flux return path of the motor ranges between at or about 1-5 mm.

[0040] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor comprises a magnet post ranging between at or about 1-5 mm.

[0041] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor geometry has two pole pairs with a pole angle of 90°. The present disclosure includes disclosure of a radial field electric motor, wherein the rotor geometry has three pole pairs with a pole angle of 60°.

[0042] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor geometry has four pole pairs with a pole angle of 45°.

[0043] The present disclosure includes disclosure of a radial field electric motor, wherein the rotor geometry has five pole pairs with a pole angle of 36°.

[0044] The present disclosure includes disclosure of an electric motor geometry optimized for propeller-based applications, comprising a stator and rotor and a rotor geometry, wherein the rotor geometry is characterized as having a pole angle of 36° or 45° or 60° or 90°, having a magnet aspect ratio (MAR) in a range of at or about 45-70%, having rotor magnets with a thickness ranging between at or about 4-15 mm, having a rotor bridge ranging between at or about 1.0-3.5 mm, having a rotor flux return path ranging between at or about 1-5 mm, and having a rotor magnet post ranging between at or about 1-5 mm.

[0045] The present disclosure includes disclosure of an electric motor geometry wherein the rotor geometry has two pole pairs with a pole angle of 90°.

[0046] The present disclosure includes disclosure of an electric motor geometry wherein the rotor geometry has three pole pairs with a pole angle of 60°.

[0047] The present disclosure includes disclosure of an electric motor geometry wherein the rotor geometry has four pole pairs with a pole angle of 45°.

[0048] The present disclosure includes disclosure of an electric motor geometry wherein the rotor geometry has five pole pairs with a pole angle of 36°.

[0049] The present disclosure includes disclosure of an electric motor geometry further comprising slots cutout from metal of the rotor to reduce weight of the motor. The present disclosure includes disclosure of an electric motor geometry wherein the slots also stream a magnetic field towards the stator without damaging flux lines.

[0050] The present disclosure includes disclosure of an electric motor geometry wherein the slots cutout from metal of the rotor are formed in any shape and size but are symmetrical and concentric around a d-axis of the rotor.

[0051] The present disclosure includes disclosure of an electric motor geometry wherein the slots cutout from the metal of the rotor are one or more curved linear slots with a width ranging between at or about 0.5-5 mm.

[0052] The present disclosure includes disclosure of an electric motor geometry wherein the slots cutout from the metal of the rotor are one or more quadrilateral slots with rounded angles having any length and a width ranging between at or about 0.5-5 mm.

[0053] BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The disclosed embodiments and other features, advantages, and disclosures contained herein, and the matter of attaining them, will become apparent and the present disclosure will be better understood by reference to the following description of various exemplary embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein:

[0055] FIG. 1 illustrates a cross-section view of a motor stator and rotor design for propellerbased vehicles, according to an exemplary embodiment of the present disclosure.

[0056] FIG. 2 illustrates a cross-section view of a motor stator and rotor design for propellerbased vehicles, highlighting the slots in the rotors that used to keep the structural integrity of the rotor in high speed, according to an exemplary embodiment of the present disclosure.

[0057] As such, an overview of the features, functions and / or configurations of the components depicted in the various figures will now be presented. It should be appreciated that not all of the features of the components of the figures are necessarily described and some of these non-discussed features (as well as discussed features) are inherent from the figures themselves. Other non-discussed features may be inherent in component geometry and / or configuration. Furthermore, wherever feasible and convenient, like reference numerals are used in the figures and the description to refer to the same or like parts or steps. The figures are in a simplified form and not to precise scale.

[0058] DETAILED DESCRIPTION

[0059] For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended.

[0060] With the introduction of electric boats, many boat manufacturers started installing electric propulsion systems in their boats. Currently, there are various electric motor geometries installed in the marine industry, from Induction Machine (IM) to Permanent Magnet Synchronous Machine (PMSM) motors. Most of these motors are adapted from the available off-the-shelf automotive motors which are not compliant with the high-power density needed for propeller-based applications. Electric motors used for marine and other propeller-based vehicles require a different optimization approach as the motor design needs to accommodate the load requirement. In particular, the Noise Vibration and Harshness (NVH) and heat is associated with higher power density. To reduce the effect of these constraints, electric motor geometry is specially designed in the present disclosure.

[0061] The present disclosure includes disclosure of a radial-field electric motor geometry 100 (also referred to herein as motor 100) optimized for propeller-based applications consisting of a stator 200 and a rotor 300.

[0062] The rotor 300 can be characterized as a mutli-pole 301 rotor 300 with a pole angle 302 ranging from at or about 36°, at or about 45°, at or about 60°, or at or about 90°, a magnet thickness 303 ranging between at or about 4-15 mm, a rotor bridge 304 ranging between at or about 1.0-3.5 mm, a flux return path 305 ranging between at or about 1 -5 mm, and a magnet post 306 ranging between at or about 1-5 mm, such as shown in FIG. 1 Another important motor indicator is the volumetric Magnet Aspect Ratio (MAR) which is defined as a volume ratio according to the following: wherein

[0063] MAR is the Magnet Aspect Ratio,

[0064] VPM is the magnet volume, and

[0065] VRS is the rotor stack volume.

[0066] The present disclosure allows to achieve a magnet aspect ratio in range of at or about 45-70% which is key to reach the motor 100 performance indicators.

[0067] The rotor 300 can further feature slots optimizing the weight of the rotor 300 while the slots are formed concentric around the d-axis of the rotor 300.

[0068] By applying the previously mentioned parameters, the motor 100 is specially designed to accommodate the characteristics of propeller-based vehicles as it has a high-power density with high torque that can support the load of propeller-based vehicles like a marine watercraft while maintaining a small size.

[0069] The high-density propeller-based motor 100 design can be used in multiple applications such as marine, airplanes, submarines, Electric Vertical Take-off and Landing aircrafts (eVTOLs), Unmanned Aerial Vehicles (UAVs), etc.

[0070] In at least one embodiment of the present disclosure, the motor rotor 300 may have other numbers of pole pairs 301 with corresponding pole angles 302 such as two pole pairs 301 with a 90° pole angle 302, three pole pairs 301 with a 60° pole angle 302, four pole pairs 301 with a 45° pole angle 302, and five pole pairs 301 with 36° pole angle 302.

[0071] In at least one embodiment of the present disclosure, the motor rotor 300 may also include slots 307 cutout from the rotor 300 metal (namely slots 307 defined within the metal of rotor 300) to reduce the motor 100 weight and stream the magnetic field towards the stator 200 without damaging the flux lines, such as shown in FIG. 1. Slot 307 cutouts from the rotor 300 metal are formed in any shape and size and are located around the d-axis of the rotor 300. The slot 307 cutout from the rotor 300 metal can, in at least one embodiment, be one or more curved linear slots with a width ranging between at or about 0.5-5 mm. Also, the slot 307 cutouts can be one or more quadrilateral slots with rounded angles having any length with the width ranging between at or about 0.5-5 mm.

[0072] In at least one embodiment of the present disclosure, the motor rotor 300 may include slots 308 around the shaft area. These slots help maintain the structural integrity of rotor 300, allowing for better thermal management and supporting higher operating speeds to minimize structural deformation, as shown in FIG. 2. In addition, the rotor 300 may include a protrusion 400 on the same side of the slots 308 to maintain the structural integrity of rotor 300.

[0073] In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have different shapes to minimize structural deformation.

[0074] In at least one embodiment of the present disclosure, the length (a first dimension 401 (dimension “a”)) between the protrusion 400 and the center of the motor 100 ranges from 10.53 mm to 63.2 mm while other surfaces of the rotor (a second dimension 402 (dimension “b”)) ranges from 10.4 mm to 63mm, such as shown in FIG. 2.

[0075] In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have a third dimension 403 (dimension “c”) ranging from 10.4 degrees to 63 degrees, such as shown in FIG. 2.

[0076] In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have a fourth dimension 404 (dimension “d”) ranging from 4 mm to 25 mm, such as shown in FIG. 2.

[0077] In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have a fifth dimension 405 (dimension “e”) ranging from 1 mm to 6 mm, such as shown in FIG. 2. In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have a sixth dimension 406 (dimension “f”) ranging from 0.5 mm to 3 mm, such as shown in FIG. 2.

[0078] In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have a seventh dimension 407 (dimension “g”) ranging from 0.125 mm to 0.75 mm, such as shown in FIG. 2.

[0079] In at least one embodiment of the present disclosure, the slots 308 in the rotor 300 may have an eighth dimension 408 (dimension “h”) ranging from 0.2 mm to 1.32 mm, such as shown in FIG. 2.

[0080] While various embodiments of devices and systems and methods for using the same have been described in considerable detail herein, the embodiments are merely offered as non-limiting examples of the disclosure described herein. It will therefore be understood that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the scope of the present disclosure. The present disclosure is not intended to be exhaustive or limiting with respect to the content thereof.

[0081] Furthermore, in describing representative embodiments, the present disclosure may have presented a method and / or a process as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth therein, the method or process should not be limited to the particular sequence of steps described, as other sequences of steps may be possible. Therefore, the particular order of the steps disclosed herein should not be construed as limitations of the present disclosure. In addition, disclosure directed to a method and / or process should not be limited to the performance of their steps in the order written. Such sequences may be varied and still remain within the scope of the present disclosure.

Claims

CLAIMS1. A radial field electric motor optimized for propeller-based applications comprising a stator and a rotor, whereby a geometry of the rotor has multiple poles with a pole angle at or between 36° and 90°.

2. The electric motor of claim 1, wherein the pole angle is 90°.

3. The electric motor of claim 1, wherein the pole angle is 60°.

4. The electric motor of claim 1, wherein the pole angle is 45°.

5. The electric motor of claim 1, wherein the pole angle is 36°.

6. The electric motor of claim 1, wherein: the motor has a magnet aspect ratio (MAR) in a range of at or about 45-70%.

7. The electric motor of claim 1, wherein: the rotor comprises magnets having a thickness ranging between at or about 4-15 mm.

8. The electric motor of claim 7, having a good magnet power in a given volume considering a magnet manufacturing process.

9. The electric motor of claim 1, wherein: the rotor comprises a rotor bridge ranging between at or about 1.0-3.5 mm to avoid flux leakage.

10. The electric motor of claim 9, wherein the rotor bridge is large enough to handle a mechanical robustness of the motor.1 1 . The electric motor of claim 1 , wherein: a flux return path of the motor is ranging between at or about 1-5 mm.

12. The electric motor of claim 11, wherein the flux return path has an optimum value between a good reluctance torque and magnetic torque.

13. The electric motor of claim 1, wherein: the rotor comprises a magnet post ranging between at or about 1-5 mm.

14. The electric motor of claim 13, wherein the magnet post is small enough to reduce or avoid flux leakage but large enough to maintain a mechanical robustness of the rotor.

15. The electric motor of claim 1, further defining: slots cutout from metal of the rotor to reduce weight of the motor.

16. The electric motor of claim 15, wherein the slots also stream a magnetic field towards the stator without damaging flux lines.

17. The electric motor of claim 15, wherein: the slots cutout from the metal of the rotor are formed in any shape and size but are symmetrical and concentric around a d-axis of the rotor.

18. The electric motor of claim 15, wherein: the slots cutout from the metal of the rotor are one or more curved linear slots with a width ranging between at or about 0.5-5 mm.

19. The electric motor of claim 15, wherein: the slots cutout from the metal of the rotor are one or more quadrilateral slots with rounded angles having any length and a width ranging between at or about 0.5-5 mm.

20. The electric motor of claim 1 , wherein: the motor rotor may define slots around a shaft area.

21. The electric motor of claim 20, wherein the slots help maintain a structural integrity of the rotor.

22. The electric motor of claim 20, wherein the slots allow for better thermal management, supporting higher operating speeds by acting like a spring to minimize structural deformation.

23. The electric motor of claim 20, wherein: the motor rotor may include a protrusion on a same side as the slots to maintain the structural integrity of rotor.

24. The electric motor of claim 20, wherein: the slots in the rotor may have different shapes acting like a spring to minimize structural deformation.

25. The electric motor of claim 23, wherein: a length (dimension a) between the protrusion and a center of the motor ranges from 10.53 mm to 63.2 mm, and a length (dimension b) ranges from 10.4 mm to 63mm.

26. The electric motor of claim 20, wherein: the slots in the rotor have a dimension (dimension c) ranging from 10.4 degrees to 63 degrees.

27. The electric motor of claim 20, wherein: the slots in the rotor have a length (dimension d) ranging from 4 mm to 25 mm.

28. The electric motor of claim 20, wherein: the slots in the rotor have a length (dimension e) ranging from 1 mm to 6 mm.

29. The electric motor of claim 20, wherein: the slots in the rotor have a length (dimension f) ranging from 0.5 mm to 3 mm.

30. The electric motor of claim 20, wherein: the slots in the rotor have a length (dimension g) ranging from 0.125 mm to 0.75 mm.

31. The electric motor of claim 20, wherein: the slots in the rotor have a length (dimension h) ranging from 0.2 mm to 1.32 mm.

32. The electric motor of claim 6, wherein: the rotor comprises magnets having a thickness ranging between at or about 4-15 mm.

33. The electric motor rotor of claim 32, wherein: the rotor comprises a rotor bridge ranging between at or about 1.0-3.5 mm.

34. The electric motor rotor of claim 33, wherein: a flux return path of the motor ranges between at or about 1-5 mm.

35. The electric motor of claim 34, wherein: the rotor comprises a magnet post ranging between at or about 1-5 mm.

36. The electric motor of claim 35, wherein: the rotor geometry has two pole pairs with a pole angle of 90°.

37. The electric motor of claim 35, wherein: the rotor geometry has three pole pairs with a pole angle of 60°.

38. The electric motor of claim 35, wherein: the rotor geometry has four pole pairs with a pole angle of 45°.

39. The electric motor of claim 35, wherein: the rotor geometry has five pole pairs with a pole angle of 36°.

40. An electric motor geometry optimized for propeller-based applications, comprising a stator and rotor and a rotor geometry, wherein the rotor geometry is characterized as: having a pole angle of 36° or 45° or 60° or 90°; having a magnet aspect ratio (MAR) in a range of at or about 45-70%; having rotor magnets with a thickness ranging between at or about 4-15 mm; having a rotor bridge ranging between at or about 1.0-3.5 mm;having a rotor flux return path ranging between at or about 1-5 mm; and having a rotor magnet post ranging between at or about 1-5 mm.

41. The electric motor rotor geometry of claim 40, wherein: the rotor geometry has two pole pairs with a pole angle of 90°.

42. The electric motor rotor geometry of claim 40, wherein: the rotor geometry has three pole pairs with a pole angle of 60°.

43. The electric motor rotor geometry of claim 40, wherein: the rotor geometry has four pole pairs with a pole angle of 45°.

44. The electric motor rotor geometry of claim 40, wherein: the rotor geometry has five pole pairs with a pole angle of 36°.

45. The electric motor rotor geometry of claim 40, further comprising: slots cutout from metal of the rotor to reduce weight of the motor.

46. The electric motor rotor geometry of claim 45, wherein the slots also stream a magnetic field towards the stator without damaging flux lines.

47. The electric motor rotor geometry of claim 45, wherein: the slots cutout from metal of the rotor are formed in any shape and size but are symmetrical and concentric around a d-axis of the rotor.

48. The electric motor rotor geometry of claim 45, wherein: the slots cutout from the metal of the rotor are one or more curved linear slots with a width ranging between at or about 0.5-5 mm.

49. The electric motor rotor geometry of claim 45, wherein: the slots cutout from the metal of the rotor are one or more quadrilateral slots with rounded angles having any length and a width ranging between at or about 0.5-5 mm.

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