Pacific Scientific R40 series motor


Thread Starter

thomas bradford

I have Pacific Scientific R40 series Motors which
have had the primary feedback tachsync removed.
These tachsyncs are 3 wire sin cos outputs/w
one sin and cos having a common connection.

Any ideas on the stator and tachsync phase
This motor/feedback combination was "brand labeled" by several drive manufacturers, some of whom had their own alignment procedures OR no
alignment required at all - the offset was adjusted in the drive. The literature with your drive should be helpful in determining which type
of commutation alignment is required.
The PacSci catalog shows the proper phasing for the Tachsyn. It does not give a procedure to set the phasing. The pacsci drives manuals I have here all seem to use resolvers -- not
tachsyns.(I know we used some motor with tacsyns in 1987-8, but the manuals seem to have vanished.)

You could try contacting Pacsci, or email them using the web form at

The tachsyn is an older, low cost, feedback device requiring specialized electronics on the servo drive to generate the commutation (6 step) and velocity information. If memory serves me, we used to have a diagram showing of the proper alignment of the tachsyn waveforms vs the back EMF of our R series motors in our catalog but we removed it some time ago.

You can call PacSci Applications Support at (978-988-9800) to get a copy of an old catalog or application note that has this information.

You can also get more information about the tachsyn device from the company ServoTek in New Jersey (

Andy Eccles
Engineering Manager
Pacific Scientific Wilmington,MA

Dale Merritt


I am a distributor in Tenn. I don't know how to do the alignment you wish to do on the motor end, but I believe there is an easy way to align it in
the drive by manually putting in the motor parameters (as if the motor was a non standard motor) and going through an alignment procedure. I have copied Jack Curll at PacSci with this email. He has helped me commutate several other mfg's motors w/ pacsci drives in the past so I am sure he can help you with this one. Good luck and let me know if this doesn't get you up and running!

God Bless!

Dale S. Merritt
Integrated Motion
407 Main St.
Suite 205
Franklin, Tn 37064
Ph: 615-599-5080
Fx: 615-599-5090

A tachsyn is not a resolver. It is a 3 phase feedback device for hall/velocity information. Each phase is 120 deg apart. It requires a special decoder circuit and will not work with an R-to-D.

Question: What drive do you plan to run with?

Most of the Tachsyn applications I have seen have been when applying the PacSci motor to the SWEO (now Baldor) analog based servo drives. I
remember working on the Tachsyn interface of another manufacturers drive as well, however I can't remember the brand. It is likely that the
drive manufacturer would have specific instructions for alignment. Contacting them will likely provide the "best" information on getting it right.

Ken Brown
Applied Motion Systems, Inc.