Don't Miss

Inverter Repaired

By on September 22, 2014










I received a call from my 14 year old daughter that the circuit breaker (CB) in our home had tripped off and the power supply to home is cut off. However the inverter is working and a fan and fluorescent light connected to inverter is working. I asked her to reset the CB and try again. She told me that it does not work and again tripped off. As I was in the office I could not find out what may be the reason for CB tripping and I asked her not to do again till I return to home in the evening.


After I went home I removed the input of Inverter and found that the CB is not tripping and power supply to whole house is restored. So I came to know that the culprit is inverter. After having dinner I settled with my tools to open investigate the reason for failure of Inverter. I opened the inverter and checked the AC input fuse and found it was OK. Then I checked the transformer and found ok.  I connected Inverter to AC 230V supply and immediately observed sparking on PCB and CB tripped off.

 inverter repair

I checked the component that was giving spark.  It is a Varistor.  I removed the Varistor and when powered ON the inverter it was working good.

Note: You can temporarily test the inverter without the Varistor just to confirm that the inverter is actually working. If you did not put in the Varistor, the inverter is no longer having protection against excessive transient voltages.

inverter repairs

So the reason for CB tripping is due to shorting of Varistor. I replaced with an equivalent Varistor and found the inverter is working and no more tripping of CB.

inverter repairing

This article is contributed by Doraiswamy from India. He is an Electrical  Electronics engineer who is a hobbyist in repair of electrical  electronics gadgets. He usually repairs the items that belong to friends and family.

Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.

P.S- Do you know of any your friends who would benefit from this content that you are reading now? If so, forward this website to your friends or you can invite your friends to subscribe to my newsletter for free in this Link.





  1. Corriette

    September 22, 2014 at 11:54 am

    great. thanks for a job well done to help us technicians

  2. Awad

    September 22, 2014 at 1:48 pm

    Very usefull.

  3. Yogesh Panchal

    September 22, 2014 at 4:20 pm


    good job and thanks for sharing

  4. Waleed Rishmawi

    September 22, 2014 at 5:02 pm

    Varistors, where would we be without them?

  5. henrynyeche

    September 22, 2014 at 6:02 pm

    thanks for the post, but if i may ask, what is the capacity of the inverter? i want to use it in my office without AC unit.

  6. Robert

    September 22, 2014 at 8:06 pm

    Thanks Doraiswamy for sharing this repair with us.

  7. Joshua oloo

    September 22, 2014 at 8:24 pm

    Thanks for the Article.keep it up.

  8. Humberto

    September 22, 2014 at 8:25 pm

    Good job, congratulations

  9. Andre Gopee

    September 22, 2014 at 9:52 pm

    Great Repair work...Thanks for sharing.

  10. Abdul

    September 23, 2014 at 7:34 am

    Thank you for the article sharing with us.
    Hope to hear more from you again.
    Abdul (Singapore)

  11. beh

    September 23, 2014 at 12:17 pm

    thanks for your article. you have done a great job to find a replacement varsitor for this invertor

  12. zed

    September 23, 2014 at 1:57 pm

    thanks for sharing the repair.

  13. jaamurthy

    September 24, 2014 at 5:28 pm

    thank you for sharing the knowledge

  14. Seun

    September 24, 2014 at 9:36 pm

    thanks for the post. It was very helpful. However, I am electronic hobbyist myself and I have a 2.4KVA MERCURY -24 volts modified sine wave inverter seating on my desk. the problem is that it does not really charge the batteries. the LCD indicator keeps showing that it is charging but after a while, when you check the batteries, one will discovered it has not been charged. Also the charging bars on the display indicating that the batteries are charging is suppose to simultaneously increase as the batteries are being charged. But in this case, the battery bar never goes beyond a single bar even after an extended period of charging.

    • beh

      September 29, 2014 at 11:29 am

      SEUN : test the out put voltages from the charger if you have enough voltages there and is steady ok then batteries are not good and must be replaced

  15. Alick Mphembera

    September 26, 2014 at 3:48 pm

    Good article. I am working on an old UPS which has not been working since 2000. I will be asking for assistance from all technicians.

    • beh

      September 29, 2014 at 11:34 am

      ALICK: test the out put of the batteries charger if you have out put voltages and is proper then you have to replace the batteries with a good ones i repaired many of them

  16. noel libreja

    October 18, 2014 at 9:12 pm

    nice job mr. yong you are really a big help for us technician and i thank you for your being generous on sharing your knowledge keep up

  17. raymundo saura

    October 21, 2014 at 8:38 pm

    thanks sir for sharing

  18. Ajinkya

    November 1, 2014 at 2:06 am

    Dear Doraiswamy,
    nice post ,
    but you need to mentioned thatb how carefully you disconnect the battery from the invetrer (you must done it).because playing with inverter without removing battery is too riskey.
    always mention thes steps because every reader is not master & perfect in electronics field means some are hobbiest

  19. Abdul Aliyu

    February 14, 2015 at 10:26 am

    I want to know hw to reset imput breaker in mercury 2.4kva inverter. Because, even if I did not turn on the inverter, the system give me out put on the lcd screen if their is light.

  20. Sir Jay

    May 17, 2018 at 2:30 pm

    I came home to turn my inverter on my MPOWER 2400, only to discover it made a continuous beep. On the LCD, it read fault. I opened it up, checked at the mosfet it was OK. I can't seem to rectify the issue...
    a friend said that MPOWER and MERCURY modSine wave inv. Always have that issue. More like there is a duration timer that shutdown the inv when it has been used for more than a year.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.