Highly efficient permanent magnet brushless motor
View Patent ↗The present invention provides a highly optimized motor design enabling an increase in torque compared to a similarly sized motor of traditional design. Additionally, the present invention enables motors that provide smooth, ripple free, operation at low speeds. These advances are provided through disclosure of slot/pole ratios that provide the stated benefits.
1. A permanent magnet brushless motor comprising:
a wound assembly comprising permeable laminations with slots;
an insulated copper wire wound with within the slots to provide electrical phases;
a field assembly comprising a permeable structure and at least 20 magnet poles arranged thereon;
wherein the wound assembly and the field assembly are arranged to produce a motive force when the electrical phases of the wound assembly are excited; and
wherein the wound assembly has a slot to pole ratio less than one to increase torque efficiency, the slot to pole ratio being selected so that a C T value is less than 6 and a Kp value is greater than 0.9 where (1) Kp=sin(1−|(pitch pu−1)|*90.0) where pitch pu=(tooth span pitch/pole pitch) and (2) C T =p Q s /N c , where p=the number of motor poles, Q s =the number of slots, and N c =the least common multiple between the slot number and the pole number.
2. The permanent magnet brushless motor of claim 1 wherein the motor has 36 slots and 46 poles.
3. The permanent magnet brushless motor of claim 1 wherein the motor has 30 slots and 38 poles.
4. The permanent magnet brushless motor of claim 1 wherein the wound assembly rotates and the field assembly remains still.
5. A permanent magnet brushless motor according to claim 1 , wherein the ratio of slots to poles is less than 0.90.
6. The motor according to claim 1 , wherein the slot to pole ratio is further chosen to create a balanced winding.
7. The motor according to claim 1 , wherein the slot to pole ratio is further chosen for optimum cogging performance.
8. The motor according to claim 1 , wherein the slot to pole ratio is chosen to enable efficient machine winding of the wound assembly.
9. The motor according to claim 1 , wherein the slot to pole ratio is chosen to have a low total harmonic distortion.
10. The motor according to claim 1 , wherein the slot to pole ratio is chosen to create a balanced winding, with optimum cogging performance, and efficient machine winding of the wound assembly.
11. The motor according to claim 1 , wherein not all of the slots are wound with insulated copper wire.
12. The motor according to claim 1 , wherein torque efficiency is increased by increasing torque density based on a volume of magnetic materials.
13. The motor according to claim 1 , wherein the slot to pole ratio is further selected to provide a total harmonic distortion (THD) less than 0.18 where THD=√((V 2 /V 1 ) 2 +(V 3 /V 1 ) 2 +(V 4 /V 1 ) 2 +(V 5 /V 1 ) 2 +(V 6 /V 1 ) 2 +(V 7 /V 1 ) 2 . . . )/V 1 % and V 1 , V 2 , V 3 are the fundamental and higher order harmonics of the generated waveform assuming a 180 electrical degree magnet span (full pitch).
14. A permanent magnet brushless motor comprising:
a wound assembly comprising permeable laminations with slots;
an insulated copper wire wound with within the slots to provide electrical phases;
a field assembly comprising a permeable structure and at least 20 magnet poles arranged thereon;
wherein the wound assembly and the field assembly are arranged to produce a motive force when the electrical phases of the wound assembly are excited; and
wherein the wound assembly has a slot to pole ratio less than one to increase torque efficiency and the slot to pole ratio is further selected to provide a total harmonic distortion (THD) less than 0.18 where THD=√((V 2 /V 1 ) 2 +(V 3 /V 1 ) 2 +(V 4 /V 1 ) 2 +(V 5 /V 1 ) 2 +(V 6 /V 1 ) 2 +(V 7 /V 1 ) 2 . . . )/V 1 % and V 1 , V 2 , V 3 are the fundamental and higher order harmonics of the generated waveform assuming a 180 electrical degree magnet span (full pitch).