Brushless PM machine construction enabling low coercivity magnets
The present disclosure provides a brushless permanent magnet machine which includes an essentially circular shaped rotor, and a pair of magnets arranged in the rotor. The magnets are each U-shaped and have a thickness direction extending along a contour of the corresponding magnet between the opposite poles of the corresponding magnet, respectively. The magnets are each composed of a non-rare earth material having a lower coercivity than a rare earth material. A direction of magnetization of each of the pair of magnets is parallel to the thickness direction of the corresponding magnet. The present disclosure also provides a method of manufacturing such a brushless permanent magnet machine.
1. A brushless permanent magnet machine comprising:
a rotor that is essentially circular shaped and having an inner circumference and outer circumference;
a pair of magnets arranged in the rotor, each magnet of the pair of magnets:
having a substantially concave contour with a pole at each end of the contour such that each pole is closer to the outer circumference than a region of the magnet between the two poles,
having a radially outward side arranged closer to the outer circumference of the rotor and an radially inward side arranged closer to the inner circumference of the rotor,
the radially outward side of each magnet defining a space in the region of the magnet between the two poles in the rotor between the outer circumference of the rotor and the radially outward side of the corresponding magnet, respectively, and
each of the pair of the magnets having a thickness direction extending along the contour of the corresponding magnet between the opposite poles of the corresponding magnet, respectively; and
a retaining component provided in each of the spaces in the rotor, each of the retaining components configured to secure a corresponding one of the magnets in place within the rotor, the plurality of retaining components being arranged entirely within the rotor;
wherein the pair of magnets are each composed of a non-rare earth material having a lower coercivity than a rare earth material, and
wherein a direction of magnetization of each of the pair of magnets is parallel to the thickness direction of the corresponding magnet.
2. The brushless permanent magnet machine according to claim 1 ,
wherein the pair of magnets are adjacent to each other in the rotor and have opposite polarities such that sides of the pair of magnets immediately adjacent to each other have the same polarity, and
wherein the direction of magnetization of each of the pair of magnets is toward the sides of the magnets which are immediately adjacent to each other.
3. The brushless permanent magnet machine according to claim 1 , wherein the non-rare earth material having a lower coercivity than a rare earth material is one of Aluminum Nickel Cobalt (AlNiCo) and Iron Cobalt Tungsten (FeCoW).
4. The brushless permanent magnet machine according to claim 1 , wherein the pair of magnets are surrounded by a material having low permeability and low conductivity.
5. The brushless permanent magnet machine according to claim 4 , wherein the material having low permeability and low conductivity has low conductivity and is non-ferromagnetic.
6. The brushless permanent magnet machine according to claim 5 , wherein the material having low permeability and low conductivity is selected from the group consisting of plastics, epoxies, polymers, fiberglass, and carbon fiber.
7. The brushless permanent magnet machine according to claim 1 , wherein the pole faces of the magnets in the pair are connected by a soft magnetic material in the rotor.
8. The brushless permanent magnet machine according to claim 7 , wherein the soft magnetic material is constituted by a material selected from the group consisting of iron, silicon-steel, and nickel-iron.
9. The brushless permanent magnet machine according to claim 1 , wherein the retaining components are non-magnetic.
10. The brushless permanent magnet machine according to claim 1 , comprising:
an extension component in one of the magnets of the pair and a mating receiving component in the other one of the magnets of the pair to receive the extension component of the one of the magnets.
11. The brushless permanent magnet machine according to claim 1 , comprising:
a cap having receiving components corresponding to the retaining rods, wherein the cap is configured to be secured with the retaining rods to secure the rotor.
12. The brushless permanent magnet machine according to claim 1 , wherein the rotor has a non-uniform diameter at a portion of the rotor in which the pair of magnets interface.
13. The brushless permanent magnet machine according to claim 1 , wherein at least one of the magnets in the pair is constituted by a continuous structure between opposite poles of the at least one magnet.
14. The brushless permanent magnet machine according to claim 1 , wherein at least one of the magnets in the pair is segmented into at least two separate pieces.
15. The brushless permanent magnet machine according to claim 1 , wherein each magnet of the pair of magnets is U-shaped.
16. A method of manufacturing a brushless permanent magnet machine, comprising:
arranging a pair of a magnets in a rotor that is essentially circular shaped and having an inner circumference and an outer circumference, each magnet of the pair of magnets:
having a substantially concave contour with a pole at each end of the contour such that each pole is closer to the outer circumference than a region of the magnet between the two poles,
having a radially outward side arranged closer to the outer circumference of the rotor and an radially inward side arranged closer to the inner circumference of the rotor,
the radially outward side of each magnet defining a space in the region of the magnet between the two poles in the rotor between the outer circumference of the rotor and the radially outward side of the corresponding magnet, respectively;
forming each of the pair of magnets to have a thickness direction extending along the contour of the corresponding magnet between the opposite poles of the magnet, respectively;
arranging a retaining component in a corresponding one of each of the spaces in the rotor, respectively, each of the retaining components being arranged to secure a corresponding one of the magnets in place within the rotor, the retaining components being arranged entirely within the rotor; and
forming each of the pair of magnets to be composed of a non-rare earth material having a lower coercivity than a rare earth material, such that a direction of magnetization of each of the pair of U-shaped magnets is parallel to the thickness direction of the corresponding magnet.
17. The method of manufacturing a brushless permanent magnet machine according to claim 16 , comprising:
arranging the pair of magnets to be adjacent to each other in the rotor and have opposite polarities such that sides of the pair of magnet immediately adjacent to each other have the same polarity and the direction of magnetization is toward the sides of the magnets which are immediately adjacent to each other.
18. The method of manufacturing a brushless permanent magnet machine according to claim 16 , wherein the non-rare earth materials having a lower coercivity than a rare earth material is one of Aluminum Nickel Cobalt (AlNiCo) and Iron Cobalt Tungsten (FeCoW).
19. The method of manufacturing a brushless permanent magnet machine according to claim 16 , comprising:
surrounding the pair of magnets in the rotor by a material having low permeability and low conductivity.
20. The method of manufacturing a brushless permanent magnet machine according to claim 16 , comprising:
connecting the pole faces of each of the pair of magnets by a soft magnetic material in the rotor.
21. The method of manufacturing a brushless permanent magnet machine according to claim 16 , comprising:
securing a cap having receiving components corresponding to the retaining rods to the retaining rods.
22. The method of manufacturing a brushless permanent magnet machine according to claim 16 , wherein each magnet of the pair of magnets is U-shaped.