Efficient high-speed electric device using low-loss materials
The invention relates generally to an electric device, such as an electric motor, a generator, or a regenerative motor, having a wound stator core made from advanced low-loss material. In preferred embodiments, the electric device is an axial airgap-type configuration. The invention provides an electric device having a high pole count that operates at high commutating frequencies, with high efficiency and high torque and power densities. Advanced low-loss materials exploited by the present invention include amorphous metals, nanocrystalline metals, and optimized Fe-based alloys.
1. A high efficiency, high power density permanent magnet electro-magnetic device comprising:
(a) at least one stator assembly including a magnetic core formed from a low-loss soft-magnetic material and having a plurality of slots wound with stator windings adapted to be connected to at least one electrical phase; and
(b) at least one magnetic field assembly including a plurality of rotor poles, the magnetic field assembly comprising a plurality of permanent magnets and being arranged and disposed for magnetic interaction with the at least one stator assembly,
wherein a torque density of the device is at least about 2.5 N-m/kg and a loss density of the device is at most about 0.2 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 500 Hz.
2. The device of claim 1 , wherein the torque density is at least about 3.4 N-m/kg and the loss density is at most about 0.4 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 750 Hz.
3. The device of claim 1 , wherein the torque density is at least about 3.8 N-m/kg and the loss density is at most about 0.6 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 1000 Hz.
4. The device of claim 1 , wherein the torque density is at least about 6.0 N-m/kg and the loss density is at most about 0.4 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 750 Hz.
5. The device of claim 1 , wherein the torque density is at least about 8.0 N-m/kg and the loss density is at most about 0.6 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 1000 Hz.
6. The device of claim 1 , wherein the soft magnetic material is an advanced, low loss material characterized by a core loss less than “L” where L is given by the formula L=12·f·B 1.5 +30·f 2.3 ·B 2.3 , wherein
L is the loss in W/kg,
f is the frequency in kHz, and
B is the peak magnetic flux density in Tesla.
7. The device of claim 6 , wherein the advanced, low loss material is at least one material selected from the group consisting of amorphous metal, nanocrystalline metal, and optimized Fe-based alloy.
8. The device of claim 1 , wherein the low loss soft magnetic material is amorphous metal.
9. The device of claim 1 , wherein the low loss soft magnetic material is nanocrystalline metal.
10. The device of claim 1 , wherein the low loss soft magnetic material is optimized Fe-based alloy.
11. The device of claim 1 , wherein the device is an axial-airgap device.
12. The device of claim 11 , having two stator assemblies and one magnetic field assembly therebetween.
13. The device of claim 1 , wherein the magnetic core is a unitary magnetic core.
14. The device of claim 13 , wherein the unitary magnetic core is also a unibody magnetic core.
15. The device of claim 1 , wherein the device is a radial-airgap device.
16. The device of claim 1 , adapted to operate continuously at a commutating frequency greater than about 500 Hz.
17. The device of claim 16 , adapted to operate continuously at a commutating frequency ranging from about 500 Hz to 3 kHz.
18. The device of claim 17 , adapted to operate continuously at a commutating frequency ranging from about 600 to 1200 Hz.
19. The device of claim 18 , adapted to operate continuously at a commutating frequency of about 1000 Hz.
20. The device of claim 1 , being an ambient air-cooled, closed-frame design and adapted to operate continuously at a rotational speed corresponding to a synchronous frequency of at least about 500 Hz with a temperature rise of at most 100° C. above ambient.
21. The device of claim 4 , being a forced air-cooled design and adapted to operate continuously at a rotational speed corresponding to a synchronous frequency of at least about 750 Hz with a temperature rise of at most 100° C. above ambient.
22. The device of claim 5 , being a liquid-cooled design and adapted to operate continuously at a rotational speed corresponding to a synchronous frequency of at least about 1000 Hz with a temperature rise of at most 100° C. above ambient.
23. The device of claim 1 , wherein a slots per phase per pole ratio of the device ranges from about 0.25 to 4.0.
24. The device of claim 23 , wherein the slots per phase per pole ratio of the device ranges from about 0.25 to 1.0.
25. The device of claim 24 , wherein the slots per phase per pole ratio of the device is about 0.5.
26. The device of claim 1 , wherein the plurality of rotor poles is at least 4 at speeds greater than about 12,000 revolutions per minute.
27. The device of claim 1 , wherein the plurality of rotor poles is at least 16 poles.
28. The device of claim 1 , wherein the plurality of rotor poles is at least 32 poles.
29. The device of claim 1 , wherein the stator windings are adapted to be connected to three electrical phases.
30. The device of claim 1 , wherein the magnetic field assembly is a rotor.
31. The device of claim 30 , wherein the device is a brushless, permanent magnet DC machine.
32. A method of manufacturing a high efficiency, high power density permanent magnet electro-magnetic device comprising:
(a) selecting an advanced, low loss soft magnetic material that is characterized by a core loss less than “L” where L is given by the formula
L= 12· f·B 1.5 +30 ·f 2.3 ·B 2.3 , wherein
L is the loss in W/kg,
f is the frequency in kHz, and
B is the magnetic flux density in peak Tesla;
(b) providing at least one stator assembly including a magnetic core formed from the low-loss soft-magnetic material and having a plurality of slots;
(c) providing stator windings in the slots, the windings being adapted to be connected to at least one electrical phase; and
(d) providing at least one magnetic field assembly, the at least one magnetic assembly including a plurality of rotor poles and a plurality of permanent magnets, the magnetic field assembly being arranged and disposed for magnetic interaction with the at least one stator assembly,
the device providing a torque density of at least about 2.5 N-m/kg and a loss density of the device of at most about 0.2 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 500 Hz.
33. The method of claim 32 , wherein said electromagnetic device is an axial-airgap device.
34. The method of claim 32 , wherein the plurality of rotor poles is greater than 4 at speeds greater than about 12,000 revolutions per minute.
35. The method of claim 32 , wherein the plurality of rotor poles is at least 16 poles.
36. The method of claim 32 , wherein the plurality of rotor poles is at least 32 poles.
37. The method of claim 32 , wherein a slots per phase per pole ratio of the device ranges from about 0.25 to 4.0.
38. The method of claim 32 , wherein the low loss soft magnetic material is amorphous metal.
39. The method of claim 32 , wherein the low loss soft magnetic material is nanocrystalline metal.
40. The method of claim 32 , wherein the low loss soft magnetic material is an optimized Fe-based alloy.
41. The method of claim 32 , wherein the magnetic core is a unitary magnetic core.
42. The method of claim 41 , wherein the magnetic core is also a unibody magnetic core.
43. A high efficiency, high power density permanent magnet electro-magnetic device system, comprising a high efficiency, high power density electro-magnetic device and power electronics means for interfacing and controlling said machine and being operably connected thereto, the electro-magnetic device comprising:
(a) at least one stator assembly including a magnetic core formed from a low-loss soft-magnetic material and having a plurality of slots wound with stator windings adapted to be connected to at least one electrical phase; and
(b) at least one magnetic field assembly including a plurality of rotor poles, the magnetic field assembly comprising a plurality of permanent magnets and being arranged and disposed for magnetic interaction with the at least one stator assembly,
wherein a torque density of the device is at least about 2.5 N-m/kg and a loss density of the device is at most about 0.2 W/cm 2 , the values of the torque density and the loss density being measured during continuous operation of the device as a generator connected to a resistive load and at a rotational speed providing electrical output at a frequency of at least about 500 Hz.