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RE: [mill_drill] problem with my mill table power feed

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  • RG Sparber
    Mark, Since the noise got worse when I ran the motor from a bench supply, I don’t think it is a problem with the drive circuit. Besides, it is just a few
    Message 1 of 14 , Nov 2, 2011

      Mark,

       

      Since the noise got worse when I ran the motor from a bench supply, I don’t think it is a problem with the drive circuit. Besides, it is just a few years old. The schematic can be found at

       

      http://rick.sparber.org/Articles/Motor/Motor052306.htm

       

      Rick

       

      From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On Behalf Of Mark
      Sent: Wednesday, November 02, 2011 7:00 AM
      To: mill_drill@yahoogroups.com
      Subject: Re: [mill_drill] problem with my mill table power feed

       



      I assume that that thing is running a DC motor? Rectifier then electrolytic filter capacitors? If the filter capacitors are original, they are probably dried out. Also, if not already installed, a couple of smaller value capacitors parallel to the filter caps to quench additional hi frequency noise. Just a guess since I don't have a schematic.

      Mark

      On 02/11/2011 9:52 AM, Malcolm Parker-Lisberg wrote:

      Rick

      You need a high voltage to reliably check insulation resistance, use your DVM on its lowest current range with a diode ladder voltage multiplier.

      Malcolm

      I don't suffer from insanity I enjoy it!

      --- On Wed, 11/2/11, RG Sparber <rgsparber@...> wrote:


      From: RG Sparber <rgsparber@...>
      Subject: RE: [mill_drill] problem with my mill table power feed
      To: mill_drill@yahoogroups.com
      Date: Wednesday, November 2, 2011, 1:37 PM

       

      Malcolm,

       

      I don’t have a megger but my low voltage DVM does read up to around 50 Meg. Do you think that would work?

       

      Rick

       

      From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On Behalf Of Malcolm Parker-Lisberg
      Sent: Wednesday, November 02, 2011 6:18 AM
      To: mill_drill@yahoogroups.com
      Subject: Re: [mill_drill] problem with my mill table power feed

       



      Rick

      Check the insulation resistance, intermittent insulation breakdown can cause the symptoms you describe.

      Malcolm

      I don't suffer from insanity I enjoy it!

      --- On Wed, 11/2/11, RG Sparber <rgsparber@...> wrote:


      From: RG Sparber <rgsparber@...>
      Subject: [mill_drill] problem with my mill table power feed
      To: valleymetal@yahoogroups.com, mill_drill@yahoogroups.com
      Date: Wednesday, November 2, 2011, 1:12 PM

       

      I have a universal motor (brush motor) moving my X axis of my mill/drill. It has worked well for many years. Recently it started to buck under load. I’ve seen this problem before and it was very high speed noise spikes getting into the SCR in the drive circuit. I replaced the SCR with one that handles 200V/microsecond where the old one was 100V/microsecond. Made no difference.

       

      I then replaced the drive with a bench DC power supply. It ran the motor nice and smooth but the electrical noise caused my DRO to go nuts. The display was constantly changing in random jumps and would not return to good values when the motor turned off. This means that the spikes were large enough to get into the slider’s electronics. I’ve never seen it that bad before.

       

      I pulled the brushes and they look well formed and smooth. I plan to pull the rotor out and give it a good cleaning plus check for shorted windings. What else could cause this kind of degradation?

       

      Thanks in advance,

       

      Rick







    • RG Sparber
      Mark, Now THAT would be a great project! ... From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On Behalf Of gmiller4396 Sent: Wednesday,
      Message 2 of 14 , Nov 2, 2011
        Mark,

        Now THAT would be a great project!

        -----Original Message-----
        From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On Behalf Of gmiller4396
        Sent: Wednesday, November 02, 2011 7:29 AM
        To: mill_drill@yahoogroups.com
        Subject: [mill_drill] Re: problem with my mill table power feed


        --- In mill_drill@yahoogroups.com, "RG Sparber" <rgsparber@...> wrote:

        Malcolm,

        There has to be an easier way. I don’t have a diode ladder voltage multiplier just laying around nor the circuit to drive it. >

        Rick

        Rick, could you take the Fux Capacitor out of your DeLorean and use it?

        Mark
      • RG Sparber
        DBN, I’ll open up that motor today and hopefully find something. As I mentioned, I did run it from a bench supply which is very clean and stiff. The motor
        Message 3 of 14 , Nov 2, 2011

          DBN,

           

          I’ll open up that motor today and hopefully find something. As I mentioned, I did run it from a bench supply which is very clean and stiff. The motor ran OK but the EMI was extremely high. A shorted winding would explain this behavior.

           

          The motor only runs in one direction. Reversal is via gears.

           

          Stay tuned…

           

          Rick

           

          From: mill_drill@yahoogroups.com [mailto:mill_drill@yahoogroups.com] On Behalf Of Druid Noibn
          Sent: Wednesday, November 02, 2011 7:53 AM
          To: mill_drill@yahoogroups.com
          Subject: Re: [mill_drill] problem with my mill table power feed

           




          Hi Rick,

           

          SCRs are well known to fire due to transients - a bit of a pain and you can imagine the work we needed to do when they were used for the early VFDs.

           

          Why it is causing a problem now, is difficult to say but you might have build-upon the commutator.  If all is smooth and clean, there can be a failing winding problem - is there any discoloration of the wires or commutator contacts?  Is the spring tension on brushes good? These sorts of problems usually sho evidence by pitted and burned brush contacts.  

           

          Also, do you have a nice "clean" power suply e.g., battery, that you can test the system on?  I don't know the votage of the motors....

           

          Is the motor run in both directions?  If yes, does the problem happen more in one direction than the other?

           

          Other points come to mind, but I'll stop for the moment.

           

          Kind regards,

          DBN

          --- On Wed, 11/2/11, RG Sparber <rgsparber@...> wrote:


          From: RG Sparber <rgsparber@...>
          Subject: [mill_drill] problem with my mill table power feed
          To: valleymetal@yahoogroups.com, mill_drill@yahoogroups.com
          Date: Wednesday, November 2, 2011, 9:12 AM

           

          I have a universal motor (brush motor) moving my X axis of my mill/drill. It has worked well for many years. Recently it started to buck under load. I’ve seen this problem before and it was very high speed noise spikes getting into the SCR in the drive circuit. I replaced the SCR with one that handles 200V/microsecond where the old one was 100V/microsecond. Made no difference.

           

          I then replaced the drive with a bench DC power supply. It ran the motor nice and smooth but the electrical noise caused my DRO to go nuts. The display was constantly changing in random jumps and would not return to good values when the motor turned off. This means that the spikes were large enough to get into the slider’s electronics. I’ve never seen it that bad before.

           

          I pulled the brushes and they look well formed and smooth. I plan to pull the rotor out and give it a good cleaning plus check for shorted windings. What else could cause this kind of degradation?

           

          Thanks in advance,

           

          Rick




        • Jerry Durand
          You might even put (or replace) a small capacitor right across the brushes in the motor. Something like a 0.001uF ceramic capacitor rated for 500V or so
          Message 4 of 14 , Nov 2, 2011
            You might even put (or replace) a small capacitor right across the brushes in the motor.  Something like a 0.001uF ceramic capacitor rated for 500V or so (they're cheap).

            On 11/02/2011 07:00 AM, Mark wrote:
            I assume that that thing is running a DC motor? Rectifier then electrolytic filter capacitors? If the filter capacitors are original, they are probably dried out. Also, if not already installed, a couple of smaller value capacitors parallel to the filter caps to quench additional hi frequency noise. Just a guess since I don't have a schematic.

            Mark

            -- 
            Jerry Durand, Durand Interstellar, Inc.  www.interstellar.com
            tel: +1 408 356-3886, USA toll free: 1 866 356-3886
            Skype:  jerrydurand 
            
          • Jerry Durand
            You might even put (or replace) a small capacitor right across the brushes in the motor. Something like a 0.001uF ceramic capacitor rated for 500V or so
            Message 5 of 14 , Nov 2, 2011
              You might even put (or replace) a small capacitor right across the brushes in the motor.  Something like a 0.001uF ceramic capacitor rated for 500V or so (they're cheap).

              On 11/02/2011 07:00 AM, Mark wrote:
              I assume that that thing is running a DC motor? Rectifier then electrolytic filter capacitors? If the filter capacitors are original, they are probably dried out. Also, if not already installed, a couple of smaller value capacitors parallel to the filter caps to quench additional hi frequency noise. Just a guess since I don't have a schematic.

              Mark

              -- 
              Jerry Durand, Durand Interstellar, Inc.  www.interstellar.com
              tel: +1 408 356-3886, USA toll free: 1 866 356-3886
              Skype:  jerrydurand 
              
            • Rick Sparber
              Jerry, That s a good idea. Thanks! Rick Rick.Sparber.org
              Message 6 of 14 , Nov 3, 2011
                Jerry,

                That's a good idea.

                Thanks!

                Rick
                Rick.Sparber.org

                On Nov 2, 2011, at 11:07 AM, Jerry Durand <jdurand@...> wrote:

                >
                >
                > You might even put (or replace) a small capacitor right across the brushes in the motor. Something like a 0.001uF ceramic capacitor rated for 500V or so (they're cheap).
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