How to Test DC motors?

Discussion in 'General Electronics Chat' started by jpietrowiak, Feb 22, 2009.

  1. jpietrowiak

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    How do you test DC motors with a meter. Is there anyway to test overall contact with the brushes. I've tested AC motors with a megger. Does the same apply?

    Thanks
     
  2. b.shahvir

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    :cool: I think a DMM (in ohms or continuiy test mode) would work fine for contact with brushes. A megger is always best for insulation test of machines.
     
  3. jpietrowiak

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    I assume then checking to ground on the motor would be the same. What about between leads like on a standard motor? Also i heard someone say once that they connect all the leads together then perform some sort of test. I always on AC motors just test each lead to ground instead of trying to tie them all together. What are your thoughts?
     
  4. jpanhalt

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    I have seen DC armatures tested with a "growler." Here is an interesting link describing testing DC motors. The use of a growler is several pages deep.

    John
     
  5. jpietrowiak

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    Not sure I follow it completely. Where do you put your meter leads. Do you remove the brushes and put your leads into the whole? Perform tests from the wires? Leave brushes in and hold them there and test? or do you have to rip apart the entire motor to test?
     
  6. b.shahvir

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    My best bet is still Megger & DMM........ sticking to simple procedures is my opinion
     
  7. Douglas Chin

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    Hi,

    I have been working with DC motors ,drives etc for over thirty years. Whilst using meter and megger meters check out the continuty and grounds it cannot really check a DC motor out propelly. What I have done is actually built a test jig to apply actual voltages to both field and armatu,re. The motor must be uncoupled from the load. As a result, the motor turn. However, one must be very careful in doing this test.

    How about those SCRs? Do not use a megger on SCRs!!!. An ohmeter can find somefaults. Again, I have built a jig to test in an active mode and by turning a pot , the scr can be made to be turned on ligtly or heavily.

    Passively checking items is not 100% acurate.

    Douglas
     
  8. jpietrowiak

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    When you say SCR's are you talking about the ones in the drive or are there some in the motor itself.

    Thanks
     
  9. docgoo

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    scrs are usually found in drives.
     
  10. BillB3857

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  11. GetDeviceInfo

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    you would test your insulation with a megger. You can check your continuity with an ohm meter. For brushes/commutator, your best check is visual. A high speed or heavy duty motor can see problems where the rotor conductors are crimped into the comm segments. If the motor is dissasembled and you have a growler available, you can test for shorts within the windings.

    Aside from that, then you want to ensure your windings are connected properly, be it series, shunt, or compound. From there you would go on to load/no load testing to evaluate your winding configuration and drive performance.
     
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