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IPM
东西研究的深入了，越来越多的新东西就冒出来了，这是一个很令人享受的过程。
这几天在rcgroups上的讨论让我受益匪浅，原贴：http://www.rcgroups.com/forums/showthread.php?t=1695789
里面有些参考文献，关于磁铁内置转子（Iternal permanent magnet, IPM）和磁铁外置转子（Surface permanent magnet, SPM）。总之IPM是一种比较流行的设计，具有转子机械强度高，成本低等优势，在应用和具体参数方面和SPM各有千秋，等有时间再好好读一下那些参考文献。
http://endless-sphere.com/forums ... =30&t=41153#p601972
http://eprints.whiterose.ac.uk/869/1/zhuzq11.pdf
This is a paper discussing the cogging, but there is a sentence in the introduction:
However, machines equipped with in- terior-magnet rotors generally have a higher torque density due to the saliency torque component and require less permanent magnet material. They also exhibit a higher demagnetization withstand capability, which is an important consideration under flux-weakening operation.
http://jap.aip.org/resource/1/japiau/v93/i10/p8769_s1
This is a paper discussing how to improve IPM motor. But in the abstract, there is again, a sentence might be useful:
The most significant benefit of the IPM rotor is its mechanical reliability, because permanent magnets are inserted in slots of soft magnetic material. On the other hand, there is significant leakage flux between adjoining permanent magnets in the soft magnetic rotor core, reducing the usable magnetic flux flowing into the stator core.
http://www.faqs.org/patents/app/20080224558#b
This is a very long and detailed description of a patent related to IPM. I can't read all, but it seems IPM is good. Hope someone who specialized in this area can summarize some useful points from this research.
http://eprints.whiterose.ac.uk/872/1/zhuzq14.pdf
Conclution of this paper:
The stator iron loss in brushless ac motors, having a surface- mounted magnet rotor and an interior-mounted magnet rotor, respectively, has been investigated under both constant torque and constant power operating modes. Whilst the interior-magnet motor facilitates extended flux-weakening operation, its iron loss can be significantly higher in the flux-weakening operating range.
http://www.aosmith.com/WorkArea/Down...et.aspx?id=474
Finally, here comes something conclusive and covering all aspects of IPM:
On the other hand, IPM motors typically employ less expensive rectangular blocks, which are placed inside slots made in the laminated rotor core. Magnet retention is therefore enhanced and yields to simplifications in the manufacturing process.
Another major type of IPM rotor (not shown) employs magnets placed in a “spoke” arrangement along the rotor radius and magnetized tangentially. The “spoke” design has the intrinsic advantage of magnetic flux concentration, so that in high polarity motors the flux density in the motor air-gap is increased. This leads the way to further performance improvement and/or size reduction. Many combinations of the magnet shape, position and number of magnets per pole is possible for IPM motors. In recent years, A. O. Smith Corporation has developed proprietary solutions to optimize designs for different applications.
magnetic field of the air-gap, in an IPM the PMs are shielded by the rotor steel that provides a leakage path for the arma- ture reaction flux. As a consequence, thinner magnets can be employed, potentially resulting in material cost savings.
The synchronous electromagnetic torque in an IPM motor has two major components (Fig. 2). The main component is the alignment torque, which is proportional with the flux linkage in the stator windings produced by the rotor magnets and with the vector component of the stator current that is in quadra- ture with the magnet flux. This current component is “active” only, i.e. only produces torque and does not contribute to the magnetization of the motor magnetic circuit. In an SPM, this is the only synchronous component of the electromagnetic torque.
In an IPM, due to the rotor variable magnetic reluctance, i.e. saliency, an additional torque component is developed. By means of electronic control, the torque angle, i.e. the angle between the magnet flux phasor and the current phasor, can be optimally set in order to increase the torque output for a given current magnitude. In the example of Fig. 2 the optimal angle is approximately 115 degrees.
Fig. 2 Electromagnetic torque components in an example IPM motor. Drive electronics tracks rotor position and controls the vector current in order to maximize torque production.
This maximum torque per amp control procedure requires a demagnetizing current component that also reduces the mag- netic circuit loading and core losses. As shown in the graph, an IPM motor has the potential of increased specific power or reduced size for the same rated power, as compared with an SPM machine. At reduced loads, both the active (quadra- ture) and demagnetizing current component are reduced yielding a relatively flat efficiency curve, yet another advantage of BLPM machines over induction motors.
http://ieeexplore.ieee.org/ielx5/41/...number=5352216
An Interesting IPM rotor design, with magnets places radially in the iron lamination core.
http://ieeexplore.ieee.org/ielx5/523...number=5259072
A direct comparison between IPM and SPM, though this IPM rotor design is a different. Seems IPM is more favorable.
[ 本帖最后由 modisc 于 2012-7-26 17:42 编辑 ] |
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楼主
发表于 2012-7-27 10:16
