Yaskawa encoder hack

  Hello there. I have a couple of mills with Yaskawa servo systems, mid 1990 BE series analog drives. They are junk, constantly blow up, very little info available, only support from Yaskawa, send us your life savings, in my case about $5 , so not enuff anyway.Using another brand of drive should be doable, the wrinkle here is Yaskawa’s unknown initial magnet sensing. The motors are sinisudialy communtated, sorry for the misspelling. The oldest ac yaz motors used what I suspect is a coded type hall sensing for initial trapezoidal communtation. The output signals were v,-v,u,-u,w,-w. , output from the encoder to the drive.The new motors have the markings on the encoder for the added signals, they are unused. I suspect the circuitry is there. Both encoders have on the glass disk , an inner ring of what I guess could be grey code. See pictures.Does anyone recognize this and have a hypothesis about how these signals would work? My guess is they are similar to the red cap Fanuc bldc signals. I have not put a scope on them  



 

It looks from the PC board that there are 12 outputs from the encoder.  A B quadrature, plus index (Z) and U V W commutation, and the differential complement of all of these.  That should be enough to run any industry standard servo drive.  AMC, Servo Dynamics, etc. have brushless drives that can take encoders like that.  Some don't need the UVW complements.
Fanuc had a different scheme for commutation on the older red cap version, the later ones are serial, so there is no ABZ signal at all.
Jon

Thank you. I have AMC amps for this application, these ones require the communtation signals until it sees the index. The thing that threw me off was the signals were differential, I’ve never seen , and I’m not an expert in this field, dual communtation signals. I take it , that I would just pick either the u,v, w or the -u,-v and -w . The AMC amps I’ve used allow for one set of halls signals. Thank you again.

Yes, that is common, just use the UV and W, and don't connect the inverted ones.