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

Thank you Jon,

I appreciate your insight! I see in the Yaskawa manual that there are
encoders from
Yaskawa that only have outputs from channels A and B with channel Z (1
ppr) on the "C" channel
just like my motor so I assume these are meant to be used with a
different amp. I
believe the C channel on the functioning motor has commutation information.

Unfortunately, I can not find a motor that matches the damaged one. I
have found another
motor that I can purchase with the same encoder but it is 1.0 hp instead
of 0.6 hp. My amp
is rated for the 0.6 hp but I was hoping to limit the current with
inductors. On the other
hand, it seems that this amp will just limit the output on its own and
function. One Yaskawa
tech thought the larger motor would work fine with this amp, but I guess
I will have to try it to
answer the question. At least the amp has overload protection.

Thanks again,

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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