BLDC: Asymetrical Zero Cross detection
Wolfgang
for detecting the Zero-cross of a sensorless BLDC I use a starpoint
reproduction and give this Neutral-Point-signal and the evaluated
Phase to a comparator. At higher speed there is no problem with zero-
cross detection. But at lower speed, the zero crossing detection is
asymmetrical: The falling edge comes late, the rising edge comes very
soon. So the following phases of the runngin motor are long - short -
long - short ....
Who knows something about this effect?
Best regards
Wolf
Bruce Varley
"Wolfgang" <Wolfgang...@aol.com> wrote in message
news:50afdcde-4ba3-4f39...@r36g2000vbn.googlegroups.com...
I'd like to try and help, but even though I'm more or less conversant with
motor theory and electronics, the terminology here is unfamiliar to me.
What's BLDC? Is this a generator or a drive application, is there speed
control electronics involved. A bit more info on the situation would assist.
Is your phase set stiff and reasonably sinusoidal?
Phil Hobbs
Cheers
Phil Hobbs
Tim Wescott
> "Wolfgang" <Wolfgang...@aol.com> wrote in message
> news:50afdcde-4ba3-4f39-a888-
de5a5f...@r36g2000vbn.googlegroups.com...
Brushless DC. Undoubtedly drive -- if it were a generator one would just
be rectifying, which is a fairly easy problem. It sounds like the OP is
designing the drive electronics -- for sensorless BLDC (i.e. brushless
without commutation sensing) you use back EMF to figure out the motor
phase.
Jerry Avins
A DC bias would cause that effect.
Jerry
--
Engineering is the art of making what you want from things you can get.
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Wolfgang
It sounds like the OP is
> designing the drive electronics -- for sensorless BLDC (i.e. brushless
> without commutation sensing) you use back EMF to figure out the motor
> phase.
>
Yes - you are right.
Wolf
iman way
I believe that my topic is useful and I would like to share my
thoughts.
THANK YOU.
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