Re: [CAD_CAM_EDM_DRO] brushless drives

dave engvall wrote:

> What is in AC brushless drives that makes them so
> expensive?
> Or is this pure marketing?
>
> The motors are not cheap but the drives are even
> worse, like 2X.

They need a special encoder that provides commutation signals
to the drive. A PWM brush drive needs 4 transistors and
doesn't care what the motor position is (brushes do the
commutation). The AC drive needs to use motor position
to compute some drive parameters, and needs 6 transistors.

Jon