本帖最后由 nongfuxu 于 2011-1-3 17:41 编辑
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13/ 本质是相同的电机，都是永磁同步电机（PMSM）。
PMSM反电势波形也未必是正弦的，是根据系统需要设计的。目前二者控制上也趋同，BLDCM也由传统的120度导通方式往180度正弦转变，其实就是PMSM的控制方式。
追根溯源，BLDCM之所以叫做直流电机，是因为从逆变器直流母线侧看进去像一个直流电机，又没有电刷，因此也叫做ECM电子换向电机。但严格来说，没有真正意义的直流电机，电枢绕组里面都是交流的，四轴飞行器械换向还是电子换向。叫BLDC是一种概念炒作。
14/ Permanent magnet motors: Are PMSMs the same as BLDCs?
There seems to be some confusion within the industry about the terms 損ermanent magnet synchronous motors?(PMSMs) and 揵rushless DC (BLDC) motors? I抳e talked with several different application engineers at different companies who抳e said that BLDCs and PMSMs are the same. But are they? It抯 true that they are both permanent magnet-based motors with the same basic structure, consisting of permanent magnets on the rotor and windings on the stator. The drive currents in the windings must be synchronized with rotor position feedback, which can come from sensors -- typically Hall effect -- on the rotor, or by evaluating the motor抯 back electromotive force (EMF). In general you抎 prefer to use a sensorless motor and save the additional part and cost.
One thing everyone agrees on is that the drive signals for the two motor types are different: A PMSM is driven sinusoidally, while a BLDC is driven trapezoidally making the PMSM much quieter, both electrically and mechanically. Plus, it has virtually no torque ripple.
So, while the basic architecture of the PMSM and BLDC motor is the same, their actual design at the detailed level is dictated by how they are driven. Here抯 how Dr. Aengus Murray of International Rectifier, explains the difference: 揂 PMSM is designed to have a sinusoidal back EMF, so the rotor is shaped to a sinusoidal flux profile. A BLDC motor needs to have trapezoidal back EMF, so the rotor needs to have a uniform flux profile.?
How does the different flux profile affect the physical motor design? 揂 BLDC needs to have a low winding inductance so it typically uses surface mounted rotor magnets. A motor with interior permanent magnet (IPM) rotor is not suitable for BLDC control because of the high inductance, but a PMSM controller can get 15% more torque from the IPM motor.?
Which raises the question, why doesn抰 everyone use PMSMs instead of BLDC motors? Because until recently programming the complex sinusoidal waveform control algorithms drove the development costs too high and required a more powerful (and more expensive) processor than what抯 needed for the relatively simple trapezoidal control of a BLDC motor. With the motor control development platforms recently introduced by companies such as IR, Microchip, Freescale, and STMicro, the algorithm development is already done for you, and you don抰 have to be a algorithm jock to use a higher-torque, low-noise, energy efficient PMSM.
都摘自: http://bbs.simol.cn/thread-35167-1-1.html
FOC并不永远是用于PMSM的专利
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