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What Could Cause A Transformer To Burn?

By on January 30, 2010

 smps transformer

Whether you are dealing with Linear or Switch Mode Power Transformer, I’m sure you have came across a burnt transformer  before. The question is, what could have cause the transformer to burn (shorted primary winding, bad smell from transformer internal parts, open primary or secondary winding and etc)? From my experience, below are some of the possible causes:

1) Lightning strike

2) Power Supply Design fault

3) Low quality of the transformer used

4) Shorted components in corresponding circuit (primary side)

5) Shorted components in the secondary side

6) Decayed glue used in surrounding circuit.

If you know of any other way that could cause a transformer to burn please share your comment -thanks!



  1. Waleed

    January 31, 2010 at 3:01 pm

    I have see this once and it took me a while to figure it out how it burnt. on of the wires soldered to the pin, was loose and it was hitting one of the wires next to it..every time I ture the tv on, I could smell something burning...and the picture on the screen it acting funny. after a long long search, I took it out and saw that loose wire..I replaced it and it worked like a charm.

    • Yousif

      March 4, 2020 at 4:52 pm

      The transformers of My swimming pool lights keep burning out since I build me pool. I got all different answers but still the transformers keep burning after 30 days or less of installing a new one. The pool technicians have reduced the ( voltage/ amp) of the transformers to prevent it from burning. They informed me if the burn occurred again then the main cable ( which connects the entire pool to the main electrical room) must be replaced as the cable is of a higher voltage. I’m really not convinced that the main cable is the reason, because the pumps and fan ventilation are working fine and no didn’t burn. By changing the cable it means my entire landscape will be destroyed!! Pls I need a professional advice and help

      • nazeal

        May 29, 2020 at 4:33 am

        where are you based

  2. admin

    January 31, 2010 at 4:59 pm

    HI Waleed,

    Thanks for sharing!


  3. kazem

    February 3, 2010 at 7:07 am

    applying overvoltage can also transformer burn.

  4. admin

    February 3, 2010 at 4:30 pm

    HI Kassim,

    Yes, the the voltage is too high the transformer will burn.


  5. sherwin

    February 9, 2010 at 9:29 am

    all info is helpfull but chech this-->> a leaky diode in a power supply could be tricky, transfomer could burn out after a while,, the funny thing is that the power will work well after replacing a defective transfomer but it would,nt last to long

  6. admin

    February 9, 2010 at 8:30 pm

    HI Sherwin,

    Thanks for sharing.



      October 29, 2017 at 1:15 am

      If I connect with dc rated voltage then primary winding may burn!!

      • Jestine Yong

        October 30, 2017 at 2:14 pm

        Hi Saibal,

        Switch mode transformer need DC current/voltage to work. Linear transformer need AC to work. You can Google for " how switch mode transformer work"


  7. evans mensah

    July 20, 2010 at 6:25 am

    what do you look for when a transformer is bunrt.?

  8. admin

    July 20, 2010 at 8:16 am

    HI Evans,
    You could see that at the side of the transformer yellow tape will turn into darker colour and have one kind of smell.


  9. Haris Eliades

    November 9, 2010 at 7:45 am


    i had a massage chair, bought it from US and used it in Europe.
    However it worked only for 3 seconds and then a "click" was heard.

    Would you think that this is a burn of the transformer? Unfortunately, we dont have anyone in my country to fix it, so any advice from you is our last resort! 🙂
    And thus if this is the case, i will try to find a similar one and replace it....

    • Alex

      February 9, 2017 at 10:54 pm

      usually in the US the voltage is 110V and in Europe is 230V, so if you use tools from the US without an adapter the transformer will burn

  10. admin

    November 10, 2010 at 9:30 am

    Hi Haris,

    I have not repair massage chair before but for any equipment, one has to check that the power supply is producing good and stable voltage. If the output is low or fluctuate then you may need to check on the power supply area. It can be dry joints, bad e-caps, leaky diodes or transistors and etc. It is not necessary the transformer problem.


  11. Desmond

    October 12, 2012 at 1:36 am

    Do you have any idea that the door bell primary transformer input get burnt even though at stanby mode?
    Do winding cycles, cooper size, poor cooper quality, insulation, or particles could cause the transformer burnt? 

    • Jestine Yong

      October 12, 2012 at 9:11 pm

      Hi Desmond,

      I'm not sure about the door bell transformer but when a transformer burnt there could be few reasons like design problem , the quality of the transformer or even related components shorted causing it to burn.


  12. ΝΙΚΟΣ

    January 12, 2013 at 1:22 pm


    • Jestine Yong

      January 12, 2013 at 8:36 pm

      HI Nikoe,

      Do you mean by adding a thermister or even a high wattage low ohm resistor?


      • Sosten

        December 25, 2020 at 11:31 pm

        Good afternoon sir I have transformer coil it burn but when I rewinding it also again burn what could by a problem, question two sir,I rewind a motor very well but when I test it runs after some sec motor almost burning and circuit breaker when off what could be the problem

        • Jestine Yong

          December 28, 2020 at 12:31 pm

          Hi Sosten,

          Good afternoon. For your information there are many factors that can cause a winding to burn. You can reread no 1 to 6 in the post. Other factors such as:
          1) Did you use the original diameter and the same quality of wire to rewind?
          2) Did you rewind it with the same length and that winding did not touch on the item casing that cause short circuit eventually burn up the winding again?
          3) After rewinding you may need an insulation tester to confirm that the winding did not short between the primary and secondary, primary to laminated steel core (linear transformer) and secondary to the laminated steel core. You can do this test on the motor too.

          Hope this helps!


  13. sawwa7

    April 25, 2016 at 7:08 pm

    the transformer could also make problems in power supply if the glue degenerate and the magnetic moment makes it vibrate under current magnetic field , this may cause a lot of problems in pictures that can't be solved unless you change the transformer !
    @Haris Eliades
    i think it's a transformer problem as far as i know that they are using 110V input for transformers in USA and 220V in Europe , so , i think you have to change the transformer and you will find the primary is open circuit

    • Nupuii pa

      July 11, 2016 at 2:40 pm

      Yes, Voltage supply of the two country could be the main reason. Fed with 110 v current, if not work, needs to chain the transformer with care.

  14. jresquival

    December 21, 2016 at 7:53 am

    I didn't know that lightning strikes cause transformer burn. Is that the only issue that lightning strikes cause to transformers? I used to live in a stormy area and I'd see electricians working with the transformers all the time.

  15. Ravindra Yadav

    August 26, 2017 at 12:57 pm

    I am a maintenance executive work in automobile industry.I have many spot welding m/c.last two month 5 spot m/c transformer burn & no reason found.please give a better reason.

  16. Sa'ad

    May 3, 2020 at 1:25 am

    a three legged diode burnt beside the transformer of my charger.
    Does that mean the charger transformer is burn???

    • Jestine Yong

      May 4, 2020 at 6:09 pm

      Hi Saad,
      Not necessarily. You need to clean the burnt area and check on the transformer to confirm if it is good or bad.


  17. Kevin Whelan

    December 23, 2020 at 12:08 am

    I have a Venmar Air Exchanger Model # 43135 my circuit board and transformer are both burned out in the unit my installer said he has never seen this before anybody got any clue of what would cause this problem


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