Re: [CAD_CAM_EDM_DRO] AC servo motor project - encoder problems

Jon,

Is it possible to create a circuit to generate a third channel Phase C
and inverse C
from channel U, V, W output?

thanks,
Keith

Jon Elson wrote:

>
> toolspindoctor wrote:
>
> >I have an AC servo motor from Yaskawa USASEM-08TV12 which I am trying
> >to control with a Yaskawa servo amp. The amp is giving an error that
> >the encoder is not wired correctly. Fortunately I have 2 amps and
> >motors. The second one is functioning. With an oscilloscope I have
> >examined the outputs from both encoders and they are identical on
> >Phase A, and B. The good motor has a Phase C output that pulses at a
> >rate similar to that on the other 2 phases. However, the new motor
> >that I am trying to get to function has an origin pulse once per
> >revolution. Thus the only difference I can see between the two
> >encoders is on the Phase C channel.
> >
> >
> >
> Yaskawa, and a number of other manufacturers, use proprietary encoder
> schemes that embed the commutation information in a "C" channel on the
> encoder. This also provides the function of the index pulse. Using
> this, there
> is no need for the traditional Hall-effect sensors used on brushless
> motors.
> The phase relationship between the C channel and the others gives the
> commutation
> info, so the motor only needs to move a couple of encoder counts for the
> drive to know
> which quadrant of a pole it is in. Without this info, the drive will
> not function.
> The drive applies power randomly to a winding and attempts to move the
> motor
> a tiny amount. If it sees 4 encoder counts on the A/B quadrature
> channel and no
> signal change on C, it goes to fault status.
>
> Without a signal on the C channel, how can the drive know which winding to
> apply power to?
>
> Jon
>
>
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