584,837 active members*
4,941 visitors online*
Register for free
Login
IndustryArena Forum > CNC Electronics > Servo Motors / Drives > Help to swap Resolver for Encoders!
Results 1 to 11 of 11
  1. #1
    Join Date
    Aug 2007
    Posts
    16

    Help to swap Resolver for Encoders!

    Dear All,

    My previous post was lost.

    Will greatly appreciate if anyone can help me with this.

    I have some AC Brushless Servo motors (8 poles) with resolvers. However, I read from some post that encoders are preferred for CNC.

    I wish to swap these with encoders from some DC servos that I have in hand. They are 1000 lines.

    My questions are:

    1) Will any encoders work? I am fitting them to my brushless 8 pole AC motor. Do I need to have commutation? how many commutation to phase and drive them 2/3/4 commutation encoders?? (sorry I am not sure what these are hence I am not sure what the right question is to ask)

    2) When I found suitable encoders, do I need to mount them at any particular angle to the pole for effective phasing/commutation/excitation of the winding etc?

    Any help is greatly appreciated!

    Thanks a lot in advance!
    fgc

  2. #2
    Join Date
    Dec 2003
    Posts
    24216
    I am assuming that these are AC sinusoidal motors and not brushless DC (BLDC)?
    If they are, the resolvers are used for commutation.
    You probabally have two choices if you want to add encoders.
    You will still need commutation so the simplest method is to add encoders to the motor shaft.
    Or you can fit an encoder that has hall effect track for start up, and then the controller uses the encoder for sinusoidal commutation.
    This all comes down to what type or make of drive are you going to use to drive the motors.
    Many sophisticated drives that accept resolver input for commutation, will extract a pseudo encoder from the resolver signal, often at programmable resolution.
    It is no mean task to fit a commutation encoder and align it to the respective poles.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
    Join Date
    Jun 2003
    Posts
    866
    I would keep shopping for motors or drives. There are some fairly modern drives that will work with resolvers. API makes some.

  4. #4
    Join Date
    Oct 2004
    Posts
    832
    Quote Originally Posted by Al_The_Man View Post
    It is no mean task to fit a commutation encoder and align it to the respective poles.
    Al.
    Can you give me any clues as to what is involved in aligning the encoder for commutation. I have a motor and the encoder has been removed. I saw a pdf on Rencos site which said to energise the first winding and align the transition of S1 to that.
    My question is how do I go about energising the winding? I tried by putting live to pin 1 and neutral to the ground pin but nothing happened, I was thinking that maybe the motor should have aligned itself to that winding. So am I doing this wrong? (I usually do )
    All help appreciated.
    Hood

  5. #5
    Join Date
    Jun 2003
    Posts
    866
    I think you may have to turn the motor until it catches, but I've never tried it.

  6. #6
    Join Date
    Oct 2004
    Posts
    832
    Quote Originally Posted by unterhaus View Post
    I think you may have to turn the motor until it catches, but I've never tried it.
    I think I did turn the shaft while energised to see if it would catch but will try again tomorrow when I get back to the workshop.

    Thanks

    Hood

  7. #7
    Join Date
    Dec 2003
    Posts
    24216
    The way I find the most accurate invloves the use of a double beam 'scope, usually you do not have access to the star point of the winding, so an artificial neutral point is made by connecting a 1k resistor to each winding and the 3 res. are connected together to form the common point for scope ref.
    The motor needs to be rotated slowly by external means, with the A winding observed, the hall effect output that you intend applying to this winding should be centered to the sinewave peak on the winding trace.
    The Renco site shows the general picture, the other two can then be identified to their respective windings the same way.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  8. #8
    Join Date
    Oct 2004
    Posts
    832
    Thanks Al, sounds like something I could manage, have a dual trace scope and I should be able to chuck the motor shaft up in the lathe and secure the motor to the saddle. The slowest speed on the lathe is 34RPM, will that be OK?

    Hood

  9. #9
    Join Date
    Dec 2003
    Posts
    24216
    That should work, whatever the 'scope can use as a sweep rate.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  10. #10
    Join Date
    Oct 2004
    Posts
    832
    Thanks Al

  11. #11
    Join Date
    Oct 2004
    Posts
    832
    Al,
    got the motor on the lathe yesterday and found that 280RPM was best for seeing on my scope. Got the S1 signal set up to centre on the peak of the A windings sine wave quite easily but when I hooked the motor up to the drive it just took off and faulted. Tried again and again but no joy. Then last night I read info saying something about motor rotation being anti clock so today I chucked the motor back in the lathe and spun it anti clock and sure enough the S1 pulse was low in the centre of the windings wave. Realigned the encoder and it now works great. Might be possible to reverse the direction in the drives software but best to have it set right in the first place I think.
    Anyway
    THANKS!!!!!!

    Hood

Similar Threads

  1. 110v single phase bridgeport motor swap
    By stanglou in forum Uncategorised MetalWorking Machines
    Replies: 22
    Last Post: 10-14-2011, 12:41 AM
  2. Spindle motor swap, or servo swap?
    By Chuck Reamer in forum Tormach Personal CNC Mill
    Replies: 28
    Last Post: 10-09-2007, 06:54 AM
  3. boss V ram spindle swap?
    By D.D.Machine in forum Bridgeport / Hardinge Mills
    Replies: 4
    Last Post: 07-05-2007, 04:53 PM
  4. Drawing swap
    By DLMACHINE in forum Rhino 3D
    Replies: 2
    Last Post: 12-20-2003, 02:30 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •