Re: [CAD_CAM_EDM_DRO] DC Brushless Motors and Drives

Nicolas Benezan wrote:

>Jon Elson wrote:
>
>
>>encoder provides the right signals for the motor's commutation. Most
>>modern servo amps figure
>>out the commutation by counting out encoder ticks from the index, but
>>then they need to
>>know how many poles the motor is and how many lines the encoder has.
>>
>>
>
>Hi Jon,
>
>just another dump question to you as expert: Do they need absolute
>encoders for this to work? If not, how do they handle the commutation
>before the first index impulse is encountered?
>
>

I'm not a great expert on this. But, there are a number of schemes.
Some do need encoders
with separate commutation channels, some don't need any encoder info at
all, they sense
the voltages from the motor windings. Others take a guess and move the
motor a little
until the encoder passes the index position. So, you just have to read
the manufacturer's
info on how this all works.

Jon