Re: [unclassified] Re: [avr-chat] BLDC control with ATmega128?

[Rick Mann]

On Feb 3, 2006, at 3:20 AM, David Brown wrote:

> Permanent Magnet Synchronous Motor.  The connections and windings are
> similar to that of a BLDC, but optomised for running with three sin  
> waves at
> 120 degree phase differences rather than BLDC trapezoid patterns.   
> Some
> motors are happy with either type of driving patterns.  BLDC  
> patterns are
> much easier to generate, while PMSM patterns give finer control (for
> example, you can lock the motor at a precise angle) and minimal  
> current
> ripple, but you need a much more powerful controller, and accurate  
> angle
> feedback (not just a hall-effect controller).

Gotcha.

So, I know you can drive a BLDC with a sinusoidal wave form, as well,  
but I don't know if you need accurate angle sensing to do it.

Even in the PMSM, do you really need 6 PWMs? Aren't three enough,  
because you only need to switch one of the two MOSFETs in each half  
bridge, the other can just be "on"?

--
Rick