Brushless DC motor

Abstract

An EC motor with a stator and a rotor mounted to a shaft. The motor has a cooling system, a molded stator housing, and an optimized rotor. The stator has teeth wound with electromagnetic coils. The teeth and coils are circumferentially distributed, with gaps between adjacent coils. The stator is molded with plastic, thereby forming axially oriented cooling channels between adjacent coil sections. Subsequently, an impeller fan draws air into the motor through an air inlet connected to an air passage. The impeller fan guides the air through the axially oriented cooling channels in the stator and exits through the air outlet. The optimized inner rotor has permanent magnets and silicon steel laminations that are circumferentially spaced and extend outward from a central bushing. Rectangular magnets are inserted in the gaps between the laminations. Wedge-shaped magnets are radially aligned with the laminations and located between the laminations and the bushing.

Description

[0001] This application is a divisional application of the invention patent application with an international filing date of January 11, 2021, national application number 202180009045.3, and titled "Electrically Commutated DC Motor".

[0002] Cross-references to related applications This application claims priority to U.S. Provisional Patent Application No. 62 / 961,446, filed January 15, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention relates to electronically commutated direct current (DC) motors (EC motors), and more particularly to EC motor air cooling systems, optimized permanent magnet rotors, and overmolded housings. Background Technology

[0004] In one embodiment, the internal rotor EC motor includes: a stator with a series of circumferentially spaced electromagnets, and a rotor located inside the stator and mounted on a shaft for rotation. The rotor has circumferentially spaced permanent magnets. An electronic controller controls the electrical energy supplied to the electromagnet coils of the stator. By controlling the electrical energy supplied to the stator coils, a rotating magnetic field is generated, which in turn attracts the permanent magnets of the rotor, causing the rotor to rotate on its shaft.

[0005] In another embodiment, the external rotor EC motor includes a stator with circumferentially spaced electromagnets. This EC motor has a rotor whose permanent magnets are positioned outside the stator. Whether internal or external rotor, the operating principle of the EC motor is largely the same: a rotating magnetic field is generated by the stator, which attracts the permanent magnets of the rotor, causing the rotor to rotate.

[0006] During operation, both the electronic controller and the stator coils generate heat. As a result, EC motors require a system to dissipate heat from the control circuitry and stator coils.

[0007] The configuration of permanent magnets and steel laminations that make up the rotor can affect the performance of an EC motor. This performance can be improved by constructing a rotor that incorporates permanent magnets of fixed dimensions and spacing around the rotor.

[0008] During operation, the switching of current in the stator coils can cause unwanted vibration and noise. Furthermore, for certain applications of EC motors, the cost and weight of motor components (including the motor housing) are important to the buyer. Summary of the Invention

[0009] To overcome the heat dissipation problem of the EC motor of the present invention, the EC motor includes an impeller fan attached to the rotor's rotating shaft. The impeller fan draws outside air into the housing of the EC motor. The outside air is directed to the impeller fan through circumferentially spaced air inlets and then through radially oriented air channels adjacent to the electronic controller. As the outside air passes through these radially oriented air channels, it absorbs heat from the electronic controller. Once the outside air is drawn through the radially oriented air channels and into the impeller fan, the impeller fan forces the air to circulate along axially oriented stator cooling channels between the stator coils. After absorbing heat from the stator coils, the air is discharged axially or radially through outlets in the housing. The impeller fan has planar fins oriented parallel to the rotor shaft, such that the cooling air flows in one direction regardless of the rotation direction of the rotor and the attached impeller fan.

[0010] In the embodiment of the inner rotor, the stator includes a structural circular core back with teeth of inwardly extending laminated steel. An energized coil is wound around and insulated from a single tooth. The tooth has a concave end defining a circular opening in which a circular inner rotor is positioned. The dimensions of the tooth and rotor provide an air gap between the concave end of the tooth and the outer circumference of the rotor.

[0011] The internal rotor EC motor includes an overmolded housing comprising a cylindrical housing body and an inwardly extending stator coil section. The stator coil section encapsulates the coils and teeth (except for the recessed ends). The housing is produced by overmolding the stator with plastic. The plastic is Rynite polyethylene terephthalate (available from DuPont) or any other plastic material with similar molding and thermal conductivity properties. Encapsulating the stator coils and teeth reduces noise and vibration. Furthermore, replacing the metal cylindrical housing body with a plastic housing helps reduce weight and lower material and manufacturing costs.

[0012] To optimize the performance of the internal rotor EC motor of the present invention, the rotor has permanent magnets and silicon steel laminations positioned around a central bushing. The silicon steel laminations are positioned around the outer circumference of the rotor and are spaced circumferentially around the rotor, with gaps between adjacent silicon steel laminations. Rectangular permanent magnets are inserted into the gaps between the silicon steel laminations. Wedge-shaped magnets are radially aligned with the silicon steel laminations and positioned between the steel laminations and the central bushing of the rotor. By adjusting the size, shape, and position of the silicon steel laminations, rectangular magnets, and wedge-shaped magnets, the rotor performance is optimized.

[0013] For an external rotor EC motor, the stator has a central bushing from which laminated steel teeth extend radially outward. Each tooth has a convex outer end. The outer surfaces of the teeth form a circle. The rotor includes a cylindrical housing with a series of spaced-apart permanent magnets attached to its inner surface. The permanent magnets are sized to have inwardly facing concave surfaces that match the convex surfaces of the teeth. The cylindrical housing and magnets are sized such that an air gap exists between the convex surfaces of the teeth and the concave surfaces of the permanent magnets. The rotor has a disc-shaped end cap to which fan blades are attached to the inner surface. The cylindrical housing also has a series of circumferentially spaced openings that act as outlets for the air pressure generated by the fan blades.

[0014] The fan of the external rotor EC motor draws air into the EC motor. The air enters the EC motor on one side of the stator, passes through a heat sink attached to the electronic circuitry, axially through the stator air passages, and exits through an outlet in the cylindrical housing of the rotor. Because the impeller fan blades are flat rather than curved, the cooling air is unidirectional regardless of the rotation direction of the rotor and fan.

[0015] To suppress vibration, the stator is overmolded with plastic. Similarly, the housing surrounding the stator and electronic controller is also overmolded.

[0016] Other objects, features, and advantages will become apparent upon taking into account the accompanying drawings and the appended claims, and upon consideration of the following detailed description of the invention. Attached Figure Description

[0017] Figure 1 This is a perspective view of the internal rotor EC motor according to the present invention.

[0018] Figure 2 This is a side front view of the internal rotor EC motor according to the present invention.

[0019] Figure 3 This is a front view of the left end of the internal rotor EC motor according to the present invention.

[0020] Figure 4 The internal rotor EC motor according to the present invention... Figure 3 The cross-sectional view seen in line 4-4.

[0021] Figure 5 The internal rotor EC motor according to the present invention... Figure 3 The cross-sectional view seen in line 5-5.

[0022] Figure 6 This is a perspective view of the internal rotor EC motor according to the present invention, with the electronic controller removed to show internal details.

[0023] Figure 7This is a right-side front view of the internal rotor EC motor according to the present invention, with the electronic controller and impeller fan removed to show internal details.

[0024] Figure 8 This is a perspective view of the stator, rotor, and impeller fan of the internal rotor EC motor according to the present invention.

[0025] Figure 9 This is a perspective view of the stator and rotor of the internal rotor EC motor according to the present invention.

[0026] Figure 10 This is a perspective view of the stator and rotor of the internal rotor EC motor according to the present invention.

[0027] Figure 11 This is a front view of the right end of the stator and rotor of the internal rotor EC motor according to the present invention.

[0028] Figure 12 This is a perspective view of a first embodiment of the rotor (ferrite rotor) of an internal rotor EC motor according to the present invention.

[0029] Figure 13 This is a front view of a first embodiment of the rotor (ferrite rotor) of an internal rotor EC motor according to the present invention.

[0030] Figure 14A and Figure 14B This is a schematic diagram of a first embodiment of the rotor (ferrite rotor) of the internal rotor EC motor according to the present invention.

[0031] Figure 15A and Figure 15B This is a schematic diagram of a first embodiment of the rotor (ferrite rotor) of the internal rotor EC motor according to the present invention.

[0032] Figure 16 This is a front view of a second embodiment of the rotor (neodymium-ferrite rotor) of an internal rotor EC motor according to the present invention.

[0033] Figure 17A and Figure 17B This is a schematic diagram of a second embodiment of the rotor (neodymium-ferrite rotor) of the internal rotor EC motor according to the present invention.

[0034] Figure 18 This is a schematic diagram of a second embodiment of the rotor (neodymium-ferrite rotor) of the internal rotor EC motor according to the present invention.

[0035] Figures 19A to 19D This is a schematic diagram of a second embodiment of the rotor (neodymium-ferrite rotor) of the internal rotor EC motor according to the present invention.

[0036] Figure 20This is a schematic diagram of a second embodiment of the rotor (neodymium-ferrite rotor) of the internal rotor EC motor according to the present invention.

[0037] Figure 21 This is a perspective view of the external rotor EC motor according to the present invention.

[0038] Figure 22 This is a perspective view of the external rotor EC motor according to the present invention.

[0039] Figure 23 This is a perspective view of an external rotor EC motor with the external rotor removed according to the present invention.

[0040] Figure 24 This is a perspective view of an external rotor EC motor with the external rotor removed according to the present invention.

[0041] Figure 25 This is a perspective view of an external rotor EC motor with the external rotor and stator cover removed according to the present invention.

[0042] Figure 26 This is a front view of an external rotor EC motor with the external rotor, stator cover, and stator removed according to the present invention.

[0043] Figure 27 This is a right-side front view of an external rotor EC motor with the external rotor, stator cover, and stator removed according to the present invention.

[0044] Figure 28 This is a side front view of the external rotor EC motor according to the present invention.

[0045] Figure 29 This is a perspective view of the rotor of the external rotor EC motor according to the present invention.

[0046] Figure 30 This is a perspective view of the stator of the external rotor EC motor according to the present invention.

[0047] Figure 31 The external rotor EC motor according to the present invention... Figure 22 The cross-sectional view seen along line 31-31. Detailed Implementation

[0048] Transfer to Figures 1 to 6 The internal rotor, electronically commutated DC motor 10 (internal rotor EC motor) has a housing 20, which includes a cylindrical controller housing 14, a cylindrical stator housing 16, and a right end portion 12. The cylindrical controller housing 14 is attached to the cylindrical stator housing 16 by means of circumferentially spaced screws 21. An electronic controller 22 is mounted inside the cylindrical controller housing 14. The internal rotor EC motor 10 has a left end 24 and a right end 26.

[0049] The internal rotor EC motor 10 has an outer stator 30 and an inner ferrite rotor 62. (Reference) Figures 8 to 11 The stator 30 has a structurally circular core back 32 with inwardly extending steel laminated teeth 34 terminating at concave ends 35. The teeth 34 are circumferentially spaced around the circular core back 32 and define openings 28 for receiving the rotor 62. Electromagnetic coils 38, insulated from the teeth 34, are wound around the teeth 34.

[0050] The right end portion 12 of the outer casing 20, the cylindrical stator housing 16, and the stator coil section 18 are manufactured by plastic overmolding the stator 30. Except for the concave end 35 of the teeth 34, the plastic overmolding encapsulates all the stator circular core back 32, stator coils 38, and teeth 34. Due to the overmolding of the circular core back 32, teeth 34, and stator coils 38, axially oriented stator coil opening channels 48 are formed between the teeth 34. Figure 5 and 7 The plastic used to overmold the stator and produce the housing 20 is Rynite polyethylene terephthalate (available from DuPont) or any other plastic material with similar molding and thermal conductivity properties.

[0051] The ferrite rotor 62 is mounted on the shaft 56. The shaft is then mounted on the bearing 58 so that the rotor and shaft rotate within the opening 28 of the stator 30. Figure 7 and Figure 9 An impeller fan 60 with impeller fan blades 61 is attached to a shaft 56, causing it to rotate together with the shaft 56 and the rotor 62.

[0052] The electronic controller 22 controls the energization of the coils 38 of the stator 30 to generate a rotating magnetic field, which interacts with a permanent magnet comprising a portion of the rotor 62 to produce rotation of the rotor 62. Therefore, the electronic controller 22 generates heat that must be dissipated from the EC motor 10. Furthermore, energizing the electromagnetic stator coils 38 to generate the rotating magnetic field also generates heat, which must be dissipated from the inner rotor EC motor 10.

[0053] To handle the heat generated by the electronic controller 22 and stator coils 38, the internal rotor EC motor 10 has an air management system including an impeller fan 60, an air inlet 44, a radially oriented air passage 46, an axially oriented stator cooling passage 48 in the stator 30, and an air outlet 50 in the right end portion 12 of the housing 20. The radially oriented air passage 46 is oriented to be adjacent to the cylindrical controller housing 14, and thus adjacent to the electronic controller 22. The proximity of the radially oriented air passage 46 to the electronic controller 22 facilitates heat dissipation from the electronic controller 22. Similarly, the axially oriented cooling passage 48 passes directly through the stator 30, between and adjacent to the stator coils 38. During operation, outside air is drawn into the air inlet 44 and, with the aid of the impeller fan 60, passes through the radially oriented air passage 46. The air is then exhausted from the impeller fan through the axially oriented cooling passage 48 and from the air outlet 50. Figure 6 As best shown, the impeller fan blades 61 of the impeller fan 60 are planar. As a result, air flows from the inlet 44 to the outlet 50 regardless of the rotation direction of the impeller fan 60. Although the air management system 42 of the present invention has been described with respect to the internal rotor EC motor 10, the operating principle of the air management system 42 is equally applicable to other electric motors.

[0054] Go to Figure 12 and Figure 13 The ferrite rotor 62 has a bushing 64 attached to the shaft 56. The bushing 64 supports ten silicon steel laminations 66, which are evenly spaced around the outer circumference 63 of the rotor 62. Rectangular permanent ferrite magnets 70 are positioned in the gaps between adjacent steel laminations 66 and are slightly recessed from the outer circumference 63 of the rotor 62. Wedge-shaped permanent ferrite magnets 68 are radially positioned between the silicon steel laminations 66 and the bushing 64 and are circumferentially spaced from each other.

[0055] Transfer to Figure 14A and Figure 14B The ferrite rotor 62 was optimized using Maxwell 2D FEA software. The width and length of the rectangular magnets 70 were varied to maximize torque output. First, the width of the rectangular magnets 70 was set, then the maximum length was determined to ensure the rectangular magnets fit snugly within the rotor without interfering with each other (see...). Figure 14A and Figure 14B Calculate the area for each configuration and select the largest area (see Table 1).

[0056] Table 1 Subsequently, the outer radius 65 of the wedge-shaped magnet 68 is increased to maximize torque output. Therefore, adding any magnet material to the rotor would degrade performance. The rotor 62 requires some areas above the wedge-shaped magnet 68 to have protrusions (ferromagnetic). Increasing the radius of the wedge-shaped magnet 68 ( Figure 15B and Figure 15A This will reduce the amount of the protrusion, thereby reducing torque output.

[0057] Figure 16 An alternative rotor embodiment is shown, namely a neodymium-ferrite rotor 74 for an internal rotor EC motor 10. The neodymium-ferrite rotor 74 has a central bushing 76 attached to a shaft 56 of the internal rotor EC motor 10. The bushing 76 supports ten silicon steel laminations 78, which are evenly spaced around an outer circumference 75. Rectangular permanent neodymium magnets 82 are positioned in the gaps between adjacent steel laminations 78, circumferentially spaced from each other, and slightly recessed from the outer circumference 75. Wedge-shaped permanent ferrite magnets 80 are radially positioned between the silicon steel laminations 78 and the bushing 76, and circumferentially spaced from each other. The outer radius 84 of the wedge-shaped permanent ferrite magnets 80 contacts the silicon steel laminations 78, and the inner radius 86 coincides with the circumference of the bushing 76. Each wedge-shaped ferrite magnet 80 has a step 88 on each side between the outer radius 84 and the inner radius 86. Adjacent steps 88 between two adjacent wedge-shaped ferrite magnets 80 create a groove that accommodates the inner end 90 of each rectangular neodymium magnet 82.

[0058] refer to Figure 17A and Figure 17B The neodymium-ferrite rotor 74 comprises alternating permanent neodymium magnets 82 and silicon steel laminations 78. Optimization was achieved by modeling the neodymium-ferrite rotor 74 and reducing the thickness of the rectangular neodymium magnets 82. Figure 17A and Figure 17B The neodymium-ferrite rotor 74 in the middle, until the performance drops below the target performance.

[0059] refer to Figure 18 Then use ratio Figure 17A and Figure 17B The rotor 74 shown uses less magnet material for the rectangular neodymium magnets 82 to simulate the internal permanent magnet spoke rotor 74. An air gap 92 is added between the rectangular neodymium magnets 82 to reduce magnetic leakage, thereby improving performance.

[0060] refer to Figures 19A to 19D The length of the spoked rectangular neodymium magnet 82 was then reduced until the performance dropped below the target performance. The air gap 92 between the neodymium magnets 82 was then filled with wedge-shaped ferrite magnets 80, which improved the performance.

[0061] refer to Figure 20 The performance of the neodymium ferrite rotor 74 is maximized by altering the inner and outer radii of the ferrite magnet 80, resulting in an optimal combination of neodymium and ferrite magnets 82 that minimizes cost and maximizes performance. The cost of the ferrite rotor 62 is lower than that of the neodymium-ferrite rotor 74 because neodymium is an order of magnitude more expensive per kilogram compared to ferrite. Neodymium also has a higher magnetic flux than ferrite. For these reasons, the neodymium-ferrite rotor 74 is more efficient than the ferrite rotor 62, but also more expensive.

[0062] A second implementation of the electronically commutated DC motor is the external rotor EC motor 110. In Figures 21 to 31 The diagram illustrates an external rotor EC motor 110 according to the present invention. The external rotor EC motor 110 has a housing comprising a cylindrical controller housing 112 and a cylindrical stator cover 150. A stationary stator 130 is attached to the cylindrical controller housing 112 and the cylindrical stator cover 130 by means of a connecting piece 114, a cover gasket 154, a stator column 140, and connecting screws 156 screwed into the stator column 140. Figure 30 The electronic controller 116 is mounted inside the cylindrical controller housing 112. The heat sink 120 is thermally attached to the electronic controller 116, thereby dissipating heat generated by the electronic components within the electronic controller 116. Figure 21 , Figure 23 , Figure 25 , Figure 26 and Figure 27 An electrical connector 118 is provided to connect power and control signals to the external rotor DC motor 110.

[0063] refer to Figure 23 , Figure 24 , Figure 25 and Figure 30 The stationary stator 130 has a bushing 132 in which a stator bearing 144 is fitted. A reinforcing rib 142 radiates from the bushing 132 and terminates at its distal end in a stator post 140, as previously described, which connects the stator 132 to the cylindrical controller housing 112 and the stator cover 150. Figure 30In the specific embodiment shown, the stator 130 has 12 individual stator silicon steel laminated teeth 134. Gap or air passages 138 circumferentially separate the individual teeth 134. Each tooth 134 (not shown) is wound with a conductive electromagnetic coil to generate a rotational electromagnetic force as commonly understood in the art. The stator 130 has a plastic overmolded structure 136 that covers the teeth 134 and the electromagnetic coil except for the protruding tooth surface 146. The overmolded structure 136 further leaves gaps or air passages 138 between the individual teeth 134. As mentioned above, the plastic used for the overmolded structure is Rynite.

[0064] The rotor 160 includes a bushing 164 to which a rotor shaft 166 is fixed. The rotor shaft 166 is mounted to rotate within a stator bearing 144. Figure 31 End cap 168 extends from bushing 164 and terminates in cylindrical rotor housing 162. End cap 168 has reinforcing ribs 170 on its outer surface. The inner surface of end cap 168 includes impeller fan 174 (…). Figure 29 The impeller fan 174 includes an inner fan blade 176 extending radially in a planar plane and an outer fan blade 178 extending radially in a planar plane. The cylindrical rotor housing 162 has a plurality of air outlets 172 spaced apart around its periphery. A series of spaced permanent magnets 182 are attached around the inner surface of the cylindrical rotor housing and are axially offset from the air outlets 172.

[0065] During operation, the rotating magnetic field generated by the teeth 134 of the stator 130 interacts with the permanent magnet 182 of the rotor 160, causing the rotor 160 to rotate on the rotor shaft 166 within the bearing 144. As the rotor 160 rotates, fan blades 176 and 178 draw outside air into the shroud intake opening 152, through the radiator 120, through the stator air passage 138, and into the impeller fan 174. Figure 31 As shown by line 180, fan blades 176 and 178 then expel air through outlet 172. As a result, outside air first cools the radiator 120, thus keeping the electronics of the electronic controller 116 cool. Next, outside air passes through stator air passage 138, thus keeping the stator 130 cool. Because fan blades 176 and 178 are flat rather than curved, outside air is drawn into the shroud inlet 152, through the stator air passage 138, and expelled through outlet 172, regardless of the direction of fan 174's rotation.

[0066] Although the invention has been described with reference to preferred embodiments, it should be understood that variations and modifications can be made within the principles and scope of the invention as described herein and as set forth in the appended claims.

Claims

1. An inner rotor for an electric motor, comprising: Bushings for supporting circumferentially spaced steel laminations, rectangular permanent magnets positioned in the gaps between adjacent steel laminations, and wedge-shaped permanent magnets radially positioned between the steel laminations and the bushings.

2. The inner rotor according to claim 1, wherein the rectangular magnet is a ferrite magnet and the wedge-shaped magnet is a ferrite magnet.

3. The inner rotor according to claim 1, wherein the rectangular magnet is a neodymium magnet and the wedge-shaped magnet is a ferrite magnet.

4. A rotor for an internal rotor electronically commutated DC motor, comprising: a. A center bushing connected to a shaft for rotation; b. Outwardly extending silicon steel laminations, the silicon steel laminations being positioned around the circumference of the rotor and spaced circumferentially around the rotor, with gaps between adjacent silicon steel laminations; c. A first permanent magnet, which is inserted into the gap between the silicon steel laminations; d. A second permanent magnet, which is radially aligned with the silicon steel laminations and located between the steel laminations and the central bushing of the rotor.

5. The rotor according to claim 4, wherein the first permanent magnet is rectangular and the second permanent magnet is wedge-shaped.

6. The rotor according to claim 4, wherein the first permanent magnet is a neodymium magnet.

7. The rotor according to claim 4, wherein the second permanent magnet is a ferrite magnet.

8. The rotor of claim 5, wherein adjacent second wedge-shaped permanent magnets have a step on each side, the step creating a groove that receives the first rectangular permanent magnet.

9. The rotor according to claim 4, wherein the second wedge-shaped permanent magnet is replaced by a gap.

10. A rotor for an internal rotor electronically commutated DC motor, comprising: a. A center bushing connected to a shaft for rotation; b. Outwardly extending silicon steel laminations, the silicon steel laminations being positioned around the circumference of the rotor and spaced circumferentially around the rotor, with gaps between adjacent silicon steel laminations; c. A first permanent magnet, inserted in the gap between the silicon steel laminations; and d. A second permanent magnet, which is radially aligned with the silicon steel laminations and located between the steel laminations and the central bushing of the rotor. The first permanent magnet is rectangular in shape and has a rectangular region in a plane perpendicular to the axis, and the second permanent magnet is wedge-shaped with a radius.

11. The rotor according to claim 10, wherein the first permanent magnet is a neodymium magnet and the second permanent magnet is a ferrite magnet.

12. The rotor of claim 10, wherein adjacent second wedge-shaped permanent magnets each have a step on each side, the step creating a groove that receives a first rectangular permanent magnet.

13. A rotor for an internal rotor electronically commutated DC motor, comprising: a. A center bushing connected to a shaft for rotation; b. Outwardly extending silicon steel laminations, the silicon steel laminations being positioned around the circumference of the rotor and spaced circumferentially around the rotor, with gaps between adjacent silicon steel laminations; c. A first permanent magnet, inserted in the gap between the silicon steel laminations; and d. A second permanent magnet, which is radially aligned with the silicon steel laminations and located between the steel laminations and the central bushing of the rotor. The first permanent magnet is a neodymium magnet, and the second permanent magnet is a ferrite magnet.

14. The rotor of claim 13, wherein the first permanent magnet is rectangular in shape, having a rectangular region in a plane perpendicular to the axis, and the second permanent magnet is wedge-shaped with a radius.

15. The rotor of claim 13, wherein adjacent second wedge-shaped permanent magnets each have a step on each side, the step creating a groove that receives a first rectangular permanent magnet.

16. A rotor for an internal rotor electronically commutated DC motor, comprising: a. A center bushing connected to a shaft for rotation; b. Outwardly extending silicon steel laminations, the silicon steel laminations being positioned around the circumference of the rotor and spaced circumferentially around the rotor, with gaps between adjacent silicon steel laminations; c. A first permanent magnet, inserted in the gap between the silicon steel laminations; and d. A second permanent magnet, which is radially aligned with the silicon steel laminations and located between the steel laminations and the central bushing of the rotor. Each of the adjacent second wedge-shaped permanent magnets has a step on each side, the step creating a groove that accommodates the first rectangular permanent magnet.

17. The rotor of claim 16, wherein the first permanent magnet is rectangular in shape, having a rectangular region in a plane perpendicular to the axis, and the second permanent magnet is wedge-shaped with a radius.

18. The rotor according to claim 16, wherein the first permanent magnet is a neodymium magnet and the second permanent magnet is a ferrite magnet.

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