20 April 2011

Commutator Sparking

Commutator is an essential part of a DC Motor. DC Supply to the Armature of a DC Motor is fed through Carbon Brushes and Commutator. The most common fault observed in DC Motor is sparking of Commutator. The below video shows sparking from a commutator.

The common reason for spark from commutator is improper brush contact. This can be due to 
  1. Defective brush holder, 
  2. Worn out carbon brushes, 
  3. Uneven condition of commutator. 
  4. Defective armature winding
The sparking create pitting of commutator and as we operate the motor spark will increase and will seriously damage commutator.  Spark will make carbon brush burn and it will worn out very fast. The below picture shown damage to the commutator of above motor. Here the segments are worn out at particular (at the place of carbon brushes) part of commutator.  That create sparking. It can be rectified by polishing the commutator. Every time after polishing the commutator it should be ensured that proper undercut is given to the mica between the segments.


  1. hey i was going through your blog and found very informative... really appreciate your effort.

    I am also working for rewinding and balancing shop for motor repair. Currently i am facing a problem With DC Motor.problem is mentioned below:
    1. DC motor was overhauled.Serviced Field Interpole and armature windings.all windings are in good condition with 2000 Mohms value.
    2.Polished the commutator,,drop tested. found ok.
    3.Brush and carbon holder is in good condition.

    Now the problem is motor is giving heavy sparking on load. Application of motor is boom hoist motor.

    On No load motors runs smooth no sparking,no vibration.

    Why it's giving heavy spark on load and we opened twice the motor but not able to get the root cause.

    can you help out ?

  2. Dear anonymous, are you talking about boom hoist motor of a machine where an MG set is used for various operations using Ward-Leonard System? If that is so, i can suggest you to check the Hoist generator connection or its output voltage at different loads whether there is any over-voltage in the generator circuit,which is likely to cause sparking in the motor connected to the generator.

  3. Dear Manikandan O V
    I am really very impressed by reading your blog. you really had a lot of hand on experience regarding to electrical motors. I have 04 number of DC motors rating 54kw working in parallel. So all 4 motors driving single machine and their shafts are connected through a Gear.
    Now one Motor of 54kw is damaged so we have 60 kw DC motor with same RPM in spare. So can we use 60kw motor in parallel with 3 number of 54kw motors having same RPM.??????????
    please send your remarks what will be the effect on behaviour.
    Hussain Ahmed

  4. Dear Manikandan,
    i am facing the same problem of a sparking on commutator on DC motor 350kw. we r using this motor in Rolling mill plant. I am getting sparking on commutator with load. we checked the c/brushes and commutator condition found healthy. but still didnt minimise the sparking... pls suggest me.

  5. You can check the drive part of the system. If the motor is fed from a DC thyristor drive, unbalance in three phases arising because of problem in the firing circuit could result in sparking. It is likely that only 4 thyristors are firing instead of 6.

    View pages at http://www.drives.zymichost.com

  6. can u please suggest me the applications where sparking in dc motor can be dangerous??

  7. Thanks for your information. It is very helpful

  8. HI i just finished rebuilding my starter but i have a problem... the starter is throwing a lot of sparks at each end of the starter mainly. Do you think it could be the bushings fitted incorrectly therefore causing the armature to float/wobble and be the cause of the sparking or the washers being improperly placed? Any ideas???

  9. Nice post . I really pleased to you for your post . And i would love to thank to you also . You have included a lot of information about the facility of a new and an used car .Its really important to know .Thanks for all of this .

    Carbon Brushes

  10. Thanks for sharing this blog. I like this blog very much. Really such an nice and decent information shared here with awesome !

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  11. the information given is helpful

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  13. Thanks for the share. I do have a problem with my AC motor for a table saw with sparking on the brushes and commutator and upon inspection I notice that it is only on two adjacent commutator bars. I remember from my days in the Navy that this can be fixed by shorting out two of the commutator bars although I can't remember which ones. Would you know how to do it? Thanks.

  14. Effects of sparking at commitator segment.....


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