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himalaya
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01.16.2009, 02:56 AM

Quote:
Originally Posted by lincpimp View Post
So, as I understand it the esc has a certain rpm limit on 2 pole, why would it have half that limit on 4poles?

The phases much switch more often on a higher pole motor per rotation than on a lower pole count motor. How else does the esc do it?
Yes, you're right, a high pole count motor requres the ESC to commutate faster than a low Pole motor, but that adds no more stress to the MOSFETs. Most ESC has fixed working frequency, MOSFETs are switching on/off according to this frequency. Faster phase changing results fewer switching times in a single commutation cycle. View from a longer period, say one second, the MOSFETs turn on/off the same times as slow phase changing situation.

An ESC's RPM limit comes from the phase detect circuitry, and how fast the MCU can safely process the detected phase information, not the FETs.


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Last edited by himalaya; 01.16.2009 at 03:02 AM.
   
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