Sunday, February 12, 2012

How an Inverter Functions, How to Repair Inverters - General Tips

It is rather futile discussing how to repair DC to AC inverter until one becomes fully informed regarding how does an inverter work. The following content walks you through both the aspects which can prove very useful to any electronic technician.Stages of an Inverter


As the name suggests DC to AC inverter is an electronic device which is able to convert a DC potential normally derived from a lead-acid battery into a stepped-up AC potential which may be quite comparable to the voltage that is found in our domestic AC outlets.


Although repairing sophisticated inverters are not easy and requires expertise in the field. Inverters which provide sine wave outputs or the ones which use PWM technology to generate modified sine wave can be difficult to diagnose and troubleshoot for the folks who are relatively new to electronics. However, simpler inverter designs that involve basic operating principles can be repaired even by a person who is not specifically an expert with electronics.


Before we move into the fault finding details it would be important to discuss how does an inverter work and the different stages normally an inverter may comprise:


An inverter normally may be divided into three important stages viz. oscillator, amplifier and the transformer output stage.


Oscillator: This stage is basically responsible for the generation of oscillating pulses either through an IC circuit or a transistorized circuit. These oscillations are basically the productions of alternate battery positive and negative (ground) voltage peaks with a particular specified frequency (number of positive peaks per second.) Such oscillations are generally in the form of square pillars and are termed as square waves, and the inverters operating with such oscillators are called square wave inverters.


The above generated square wave pulses though are too weak and can never be utilized to drive high current output transformers. Therefore these pulses are fed to the next amplifier stage for the required task.



Booster or Amplifier (Driver): Here the received oscillating frequency is suitably amplified to high current levels using either power transistors or Mosfets. Though the boosted response is an AC, but is still at the battery supply voltage level and therefore cannot be used to operate electrical appliances which work at higher voltage AC potentials. The amplified voltage is therefore finally applied to the output transformer secondary winding.


Output Transformer: We all know how a transformer works; in Ac/DC power supplies it is normally used to step-down the applied input mains AC to the lower specified AC levels through magnetic induction of its two windings. In inverters a transformer is used for similar purpose but with just opposite orientation, i.e. here the low level AC from the above discussed electronic stages is applied to the secondary windings resulting in an induced stepped up voltage across the primary winding of the transformer. This voltage is finally utilized for powering the various household electrical gadgets like lights, fans, mixers, soldering irons etc.


DC to AC Inverter, Repairing Tips

In the above explanation a couple of things become very critical for obtaining correct results from an inverter. Firstly the generation of the oscillations, due to which the process of voltage induction is able to take place across the windings of the transformer. The second important factor is the frequency of the oscillations, which is fixed as per the country’s specifications, for example countries that supply 230 V, generally have a working frequency of 50 Hz, in other countries where 120 V is specified mostly work at 60 Hz frequency.


Sophisticated electronic gadgets like TV sets, DVD players, computers etc. are never recommended to be operated with square wave inverters. The sharp rise and fall of the square waves are just not suitable for such applications.


However there are ways through more complex electronic circuits for modifying the square waves so that they become more favorable with the above discussed electronic equipment. Inverters using further complex circuits are able to produce waveforms almost identical to the waveforms available at our domestic mains AC outlets.

How to Repair an Inverter


Once you get well versed with the different stages normally incorporated in an inverter unit as explained above, troubleshooting becomes relatively easy. The following tips will illustrate how to repair DC to AC inverter:


Inverter is “Dead”: Check battery voltage and connection, check for a blown fuse. If that’s OK, open the inverter outer cover and do the following steps:


Locate the oscillator section; disconnect its output from its preceding stage and using a frequency meter confirm its proper working. No frequency or a stable DC indicates a possible fault with the stage. Check its IC and the associated components for the remedy.


In case you find the oscillator stage working fine, go for the next stage i.e. the amplifier stage. Check each device using a digital multimeter, you may have to completely remove them from the board for the particular tests. If you find a particular device to be faulty just replace it with a new one.


Sometimes transformers also become the major cause for a malfunction. Check for an open winding or a loose internal connection in the associated transformer. If you find it to be suspicious, immediately change it with a new one.


Although it won't be that easy to learn everything about how to repair DC to AC inverter from this chapter itself, but definitely things will start "cooking" as you delve into the procedure through a lot of practice and some trial and error.

Still have doubts...feel free to post your specific questions here.

80 comments:

  1. i get 240volts at d transformer output at 13 volts but when i plug my t.v (79watts) d volt drops to 201volt with a bulb of 60watts it drops again to 180.am using 4 mosfet(irfp250) 2 in parallel with 1000watts tranformer

    ReplyDelete
    Replies
    1. You didn't mention the battery AH, you would require at least a 32 AH battery for operating those comfortably.

      Regards.

      Delete
  2. Replies
    1. 88 AH is OK, I will need to see the circuit diagram, without seeing I cannot diagnose the problem.

      Probably you will need to connect more mosfets in parallel for pulling the power to higher levels.

      Delete
  3. u av d circuit in ur box already

    ReplyDelete
    Replies
    1. which circuit are you referring to?

      Delete
    2. Increase the mosfet gate resistor values, connect a couple of more mosfets in parallel, I hope you know how to connect them in parallel.
      Each mosfet should have its own individual gate resistor.
      Mount all of them on large heatsinks.
      For safety use separate heatsinks for each mosfet.

      Regards.

      Delete
  4. Good day,

    I would like to make an efficient automatic relay switch between 220V AC main and 220V AC inverter out, can you help me out? I have experimentally made relay connections already but I think its not efficient coz my relay is always on at standby. The relay is directly supplied by 220v ac main or 12v dc from 220v ac main which uses NC pin for 220v inverter output, NO for 220v main and COMM pin for UPS final output. But I was thinking that I misused the relay by letting it ON 24/7. I was thinking that it would be better that the car battery will power the relay when the 220v ac main is lost. A simple transistor circuit might be able to do this job but I dont know how to make it coz I haven't studied electronics.

    I hope you can help me out.

    Thanks.

    I have made an automatic car batter charger using your simple two transistor circuit with relay. It works well.

    ReplyDelete
    Replies
    1. I guess you used the battery charger DC output for powering the relay, that is why the relay never switches off because it is always getting the power from the battery and also from the mains DC when 220 v is present.
      In that case just use two diodes, and connect them in the following manner.

      join the anode of the two diodes together and connect the cathode of one diode to the relay and the other diodes cathode to the battery positive, in this way only the mains 12v DC will reach the relay and the battery DC will remain blocked.
      The relay will be on only when mains 220V is present and will switch off when 220V power fails.
      I hope you got the point.

      Regards.

      Delete
    2. Thanks for the reply, I would like to have the relay that is switched off when the 220V AC mains is present and will turn off if the 220V AC mains is lost taking its power from the battery.

      Kindly confirm this diagram:

      http://cindybob.com/halloween/circuits/relaydriver.html

      I found just now please advice me if I'm correct with me understanding, that when the input voltage of 4Vdc or greater is lost it will trigger to turn on the relay taking its power from power supply, in my case battery. I'll just put a small transformer to supply the circuit input of 4VDC and up.

      Thanks

      Delete
    3. The diagram is OK but unnecessarily complicated, why would you need an extra transistor stage when the relay can be directly driven from the power supply itself.

      Using battery for driving the relay will unnecessarily waste some battery power.

      It's your wish you can use the shown circuit, technically it's OK.

      Regards.

      Delete
    4. Good day,

      I'm a little confused about the two diode connection, please enlighten me.

      I also tried that circuit in the link but it doesn't work as described in its description.

      as described:
      "The following circuit will allow you to drive a 12V relay using logic voltage (an input of 4V or greater will trip the relay)"

      in my understanding, the relay will turn off if there is a supply of 4V in the input, but as I have made, the relay is ON when 4V is present and OFF when lost.

      What I'm looking is the circuit that will turn off the relay when there is an input of 4V and UP (from 220V AC main), taking its power from the battery. In this case the relay will remain cool during a long period of normal power condition.

      But in the case that what I'm looking for is not possible, I just want to ask if it is ok for the relay to be remained ON 24/7? Because I observe its hot.

      Thank you very much.

      Delete
    5. You would either require one more transistor to revert the actions or simply replace the NPN transistor in the circuit with a PNP one.
      Use a BC557 in place of the exixting 2N3904 transistor and do the connections exactly as suggested below:
      Keep the 2.2K resistor as it is.
      Remove the 4.7K resistor, it's not required.
      Connect the emitter of the transistor to the POSITIVE of the battery.
      Connect the relay coil across the collector of the transistor and NEGATIVE of the battery.
      CONNECT A DIODE ACROSS THE RELAY COIL, WITH ITS CATHODE CONNECTED TO THE COLLECTOR AND ANODE TO THE GROUND. The diode protects the transistor from the generated back emfs from the relay coil.
      The other diode is not required.
      Connect the battery negative with the ground of the circuit.
      Now as long as a POSITIVE (from the power supply) is applied directly across the base of the transistor and ground, the transistor remains shut off, the moment the POSITIVE supply is removed the transistor gets biased through the 2.2K resistor and activates the relay.

      Regards

      Delete
    6. Hi!

      I've made a simulation of the circuit you have given, it seems to work well.

      kindly check if I got mistaken:

      http://www.youtube.com/watch?v=IQANszF6g34

      Delete
    7. Great! you interpreted my explanation correctly. I'll publish this video in the article "how to make a relay driver stage"

      If you could tell your good name to me, I would like to include it there.

      Regards.

      Delete
    8. I'm Ronald, thanks a lot for your circuit.

      Delete
    9. You are welcome Ronald, I have shared the video in the following link:

      http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-make-relay-driver-stage-in.html

      Regards.

      Delete
  5. av send u my circuit already,femmza@gmail.com

    ReplyDelete
  6. My inverter keeps burning down two transistors H1061, it's an inverter of 500W, with 12 transistors 2N3055, and 4 9013 or so, my question would be: what with I should replace these H1061? Thanx in advance

    ReplyDelete
  7. How did you connect the FETs (tell me the connections)? Do you have the flyback diodes in place? Were these mosfets already present with the inverter or are you trying to modify the inverter using them??

    ReplyDelete
  8. H1061 are not FETs, they are "TRIPLE DIFFUSED SILICON NPN TRANSISTOR", the flyback diodes are in place, the H1061 are already present with the inverter, not trying to modify the inverter. anyway thanks for reply and for your time.

    ReplyDelete
  9. hello sir /bro this mohammed azmir im doing bussiness in inverters and batteries i have small query please solve !! now trend is going to solar inverters and solar battery is it charge in climate 25degres if climate is cool pannels are charge too batery

    ReplyDelete
    Replies
    1. Hello Muhammed,

      It's true, at lower temperatures solar panels work more efficiently and generate more current, however if a good charger/controller is utilized the excess current won't affect the battery.

      Delete
  10. Hello Swagatam,
    Thank you for endeavoring to answers everyone's questions here. I am using an inverter off-grid which is the only source of electricity where I am in West Africa. I have a Chicago Electric 1500 Watt 115 V, 60 Hz inverter. It worked great for a couple years and whenever I measured its output voltage with my multimeter, it was around 105 volts. (I assume this was due to the slightly lower peak voltage of the modified square wave it puts out.)
    Recently, and suddenly, it started putting out about 180 volts. Fortunately, my CFL bulbs did not explode the first time I realized this (I noticed something was wrong when I put on a fan and it started spinning much faster than usual), but I am afraid to damage 120 volt equipment with the high output voltage, and so I have attached a step-down transformer for now (this gives me 90 volts which lights up the CFL bulbs, but the fans run slow, and TV and stereo don't come on at all). Obviously, what I would really like to do is fix the inverter so that it puts out 115 volts again! Any ideas what the problem could be?

    Thanks in advance

    ReplyDelete
    Replies
    1. Hello Vedicaudio,

      Your inverter requires immediate attention because the fault is serious. I think the PWM section of your inverter might have stopped working.

      It would be better to get it repaired instead of using it in this abnormal conditions.

      Only an experienced technician would be able to diagnose the fault because all inverters employ slightly different topology and configurations.

      Regards.

      Delete
  11. Am through with the inverter, so how can i know the size of transformer and battery to use. and how to calculate this with the applied load to enable it last for a long time. thanks

    ReplyDelete
    Replies
    1. You can get the idea roughly by multiplying the half winding voltage with the current rating of the transformer, this will give you the wattage of the transformer....for more info, read this article:

      http://homemadecircuitsandschematics.blogspot.in/2012/02/how-to-calculate-and-match-inverter.html

      Delete
  12. HI I have a 2.5kw inverter supplied by 24 2 volts batteries and charged by solar panel. my system is 24 volts and I am in Spain. I use the system to run my pool motor. My problem is that the inverter is giving me 270 volts and that has burned my pool motor? DO you think that a the inverter can be adjusted down or could it be because I dont have the batteries and the inverter grounded...? any help would be appreciated. thanks

    ReplyDelete
    Replies
    1. Hi, the problem has nothing to do with grounding, may be it doesn't have an output regulation facility or may be it's not working.

      There's nothing manually you can do about it.

      one method would be to decrease the battery voltage to 20V to 22V, that would proportionately produce a lower voltage at the output

      Delete
  13. Please help me get the diagram and the list of parts to manufacture DC to AC inverter.

    ReplyDelete
  14. hi,i have a 1000watt inverter,it powers up,the fan comes on,usb output ok but no 240v,the fuse had blown at the back but no improvement once replaced.any ideas,thanks paul.

    ReplyDelete
    Replies
    1. sorry no ideas, there can be many different causes, can't troubleshoot without seeing...

      Delete
  15. sir how to check the power factor of inveter output with using multimeter and mathamatical calculation ??

    ReplyDelete
    Replies
    1. multimeter cannot be used for checking PF, refer to this article for more info:

      http://www.ccontrolsys.com/w/Inverter_Power_Factor

      Delete
  16. Hi,

    I have a question, I have a 600w inverter that seems to have developed a fault. The inverter is only used to power a handful of powersaver bulbs in my house when the power goes out using a 12v car battery. On my last use when normal power returned to the house I switched off the inverter from the built in switch on the inverter and then went and switched on the mains for the house. The input power was still connected to the inverter. I use a 3pin plug on each end and connect 1 end to my interter and the 2nd to a wall socket in my house. When I swithed on the main switch it tripped the trip switch in the house and I think the inverter got damaged as well. Now when I connect my inverter to my 12v battery I get a continuous buzzing sound coming from the inverter like the input power is low, even with nothing connected to the output of the inverter. I just wanted to know what could have possibly blown. The fuses are ok and when opened nothing seems to have been burnt or blown visually.

    Thanks

    ReplyDelete
    Replies
    1. Hi,

      without a proper schematic it would be difficult to correctly understand the mentioned connections, if you can provide a complete drawing then probably I can trace out if anything's blown inside.

      Delete
  17. i have an Inverx 650 VA inverter overload at no load inverter.by mistake the phase output line connected to input phase supply after that the mosfet IRF 740 fleshed away after changing them only two were short circuited the inverter goes to permanently overloading at no load with red light i have no diagram for refernce.replacing the whole line Mosfet's in parallel or something else.

    ReplyDelete
    Replies
    1. It would be difficult to guess without actually seeing the issue...so I am sorry can't figure out the problem from here.

      Delete
  18. Greetings Swagatam,
    My inverter has burned up a capacitor and the board specifies a different cap than the original, should I change the cap to the requirement printed on the board or just us the same original was 250V 470uf board has 450V 330 uf printed on it in this location

    ReplyDelete
    Replies
    1. Greetings Steven,

      It's not critical according to me, you can use either of them, as per the availability.

      Delete
  19. Hello,
    I have a Go Power 1500 inverter and was using 4 - 6v AGM batteries to power the RV. The inverter when turned on goes into it's start up procedure and when finished it goes immediately into overload. I installed 4 new (same) batteries and it continues to do the same thing.

    I disconnected the inverter when the issue first happened and the batteries swelled and started smelling so I removed those too.

    Is there a component inside the inverter that would make the inverter revert to overload even with brand new batteries and everything else is fine?
    No tripped GFCI, or inline fuses blown etc.

    I didn't open the cover and inspect for any burnt components yet and the inverter itself doesn't smell like a capacitor etc. has burned.
    Is there anywhere that repairs these as Go Power doesn't repair their units so, I was forced to buy another inverter!

    Thanks in advance.

    ReplyDelete
    Replies
    1. An overload situation might occur only under two conditions, if the connected battery voltage is much higher than the specified limits, or if the output load exceeds its predetermined level.

      As long as the battery voltage is correct and output is not over loaded, even 100s of batteries connected in parallel wouldn't cause any issues or tripping.

      So, there's certainly some other serious issue with your inverter, not something which you can diagnose at home.

      Delete
    2. Ok, understood on the non home diagnosis of the unit. Where can I send it for repairs and what is the labor charge usually to repair it? I realize parts would be a cost too.

      Go Power doesn't repair their own units as mentioned prior.

      Thanks in advance.

      Delete
    3. I am sorry, I really do not have any information regarding this.

      Delete
  20. Hello Swagatam, I damaged. I mistakenly connected mains to the output terminal of my inverter.It stopped working with fault alarm indication on its LCD. What are the likely components that could be damaged?. It is transformer type inverter.

    ReplyDelete
    Replies
    1. The power devices (mosfets) are the ones which might have got damaged, according to me

      Delete
    2. Sir i want to make a 850va inverter at home i am studying but did not get idea please provide me a complete circuit diagram with component list.my id is raj100386@gmail.com thanks

      Delete
    3. Rajesh, do the assembly as per the given diagram, the IC is 4049 the transistors are made up of TIP122 and TIP35 pairs....the capacitor value is 0.01uF, the resistor value near the capacitor is 100k, the transistor base resistors are 10k each

      Delete
  21. Hi Swagatam. My 5000W 12V to 230V PSW inverter's fan speeds up as the temperature of the unit rises (or as the amp draw increases, not sure which is the case). At lower speeds it will slow down as load or temp decreases, but if it reaches top speed, it gets "stuck" there and never returns, running at high speed, unless the unit is shut down and powered up again. How can I fix this to have it always return to lower speeds when it cools down?

    ReplyDelete
    Replies
    1. Hi Andries, it will be difficult to diagnose because different models have different circuit topologies, and configurations, which are unique to those models, so it's not possible to troubleshoot without practically seeing it.

      Delete
  22. Hi, i have a 2500 watt 12volt/240volt inverter, on the same system i also have a generator which takes over when the batteries are low. I have 2 rotatry switches operating the electric, however as expected i turn the generator power while the inverter power was also live thus putting 240 volt power to the 240 volt supply from the inverter.
    This tripped the breaker on the generator and although i have reset that the inverter now does not work.
    It has illuminations lights on it, it makes a pulsing noise and there is a slight smell of burning although the fan still works.
    What do you think? (not of me lol but of the inverter please)!!

    ReplyDelete
    Replies
    1. Hi, although im not very sure, if the smell is from the inverter while it's in switched ON positioned would certainly indicate a damaged tramsformer winding, but if it's happening in OFF position then it would need some investigation to see exactly what's burning (lol)....most probably it's the inverter winding that might have gotten slightly damaged due to the generator voltage in-surge.

      Delete
  23. I have in the motorhome a 1000 W 12v to 220V (240) inverter which produces no more than AC 200 V from the 85 Ah leisure battery. On the engine switched on it goes down to even 183 V. Please advice what could be an issue

    ReplyDelete
    Replies
    1. your batteries could be producing lower than optimal voltage or may be are not fully charged.

      you could try verifying the same by replacing them with new batteries.

      Delete
  24. My issue with a ready-made inverter is not considered here. From the beginning, this inverter worked fine for charging, but always made capacitive-input devices behave erratically when plugged in. The trackpad on the laptop doesn't move the pointer on the screen properly, and has a lot of jitter. Problem disappears when the device is unplugged from inverter. And perhaps more dangerously, a particular USB charger plugged in the 120V outlet (I know it's an inefficient use of the inverter ;) gave me a discharge from touching the metal case of the tablet. This charger doesn't have any issue when plugged in at home, even though the mains is ungrounded. Maybe it was the charger or simply static electricity build-up on me from repeatedly moving to and from the driver's seat.

    Still, how would I know what could be at fault in this case? I have no oscilloscope to verify the waveform or possible spikes, though I'll see if I can build a USB one.

    ReplyDelete
    Replies
    1. Selim, are you sure the inverter is generating the correct RMS voltage? you can confirm it by checking the output voltage with a multimeter set at AC 250V range.

      If it shows over 150V, the high voltage could be causing the issues.

      Or it may be due to the high amount of harmonics from the inverter.

      Try adding a 0.22uF/400V capacitor right across the inverter output terminals and check the results.

      Inverters normally do not have a neutral, they have an alternating phases coming out of both their outputs pins, that's very unlike our mains AC, this could be the cause of the slight shock that you are getting from the charger body.

      Delete
  25. Hello sir, i have a microtek inverter which was working nicely from couple of year but suddenly i got one problem......sometime its stop working and indication show for overload and fuse blow while its output load and fuse are ok......and when i restart the inverter then its working again......what is the reason behind this

    ReplyDelete
    Replies
    1. hello my life,
      it seems to be an internal circuit problem, which needs to be diagnosed by removing the circuit board and checking with a multimeter,,,,it would be difficult to troubleshoot by assuming.

      Delete
  26. Off grid small house system. The inverter is feeding 40v AC back over the 12v batteries. In this state, current positive terminal to ground is 8 u Amps, as measured with a multimeter. This is making 12v backup generator live to 40v ac and zaps someone when they go to start the generator. Also the 40v ac appears to be interfering (but I'm not certain) with various charging cycles from solar and wind controllers. Can you give some clues as to further fault-finding techniques or suggestions please?

    ReplyDelete
    Replies
    1. I guess the 40AC is connected with the battery through a bridge and a voltage regulator, in that case the battery could be safe, but a human could feel the zap due to his body earth passage.

      You can try isolating the 40AC to the battery section via a transformer, the primary could be rated at 40V and the secondary slightly above the battery voltage rating.

      Delete
    2. ...a schematic could have helped to understand the situation in a better way.

      Delete
  27. Hello sir, i have a microtek inverter which was working nicely from couple of year but suddenly i got one problem....wen i start it or increase load on it...... it starts generating abnormally high sound and output voltage i very low but at that tym it blows CFLs and mobile chargers....... after few minutes it will behave normal

    ReplyDelete
    Replies
    1. Hello Sharad,
      The automatic voltage correction feature of the inverter seems to be malfunctioning, it will need to be diagnosed practically, can't suggest much without inspecting.

      Delete
  28. Hii I have a 800VA Inverter & 150Amp Battery attached to it. My inverter is not showing the charging signal and indirectly charging it by overcharging the battery. Few days ago I topped up my battery by distilled water and after that I found out that the battery is not charging and over that when check with tester current is being shown on both the terminal of the battery.
    Plz let me know about the problem and give me some solution for it.

    ReplyDelete
    Replies
    1. try charging the battery with an external battery charger unit and then connect it with the inverter, the fault could be with your inverter's charging system.

      If the battery doesn't charge optimally through an external charger it would indicate a damaged or a sulfated battery and will need to be changed

      Delete
  29. Hi,
    I used my 300W inverter (12Vdc to 230Vac) to power a double tube flourescent light fitting. The total wattage of the light fitting is 130W. The tubes lit up, but then after switching off the light fitting and then switching it back on, the inverter failed. There is a red LED indication on the inverter which means that there is a fault. What could I have blown? Could the high inrush current have blown some component, or could a switching surge have blown some component? What is the most likely component in the inverter that could fail due to the inductive load which I subjected it to?
    Please reply soon, Riyaz

    ReplyDelete
    Replies
    1. Hi, Normally a good inverter will not fail even if its outputs are short circuited, so a tube light should have noway affected its operations.

      Can't say what might have happened to it without a practical examination, looks like a part failure inside..

      Delete
  30. Hello sir howcr u....
    My problem is that i m having a luminous 800va inverter 150amp battery attached to it...it's charging led were not working...so when i was repairing that board..it touched in heat sink of mosfet...after that none of the led's are working...it's not a big issue but....main problem is that inverter giving low output voltage 150 volts...on load and on no load...i measured it's battery charging amperes...which is 12amps...i tried different battery but problem is same....are mosfet's blown up??? If yes how can i check them with multimeter....???

    ReplyDelete
    Replies
    1. Hello nitin, if the output is low then it could mean a few of the fets are fried or working asymmetrically...check the amp without load by connecting an ammeter in series with battery positive...if it's high without load would confirm a serious fet malfunction

      Delete
    2. Hello sir...there are two series of 5-5 mosfets each in my inverter...so one mosfet was looking cracked...so i changed whole series of 5 which was chn 608 with chn 347...when i connected battery it was working...but whenever i put load on it...,it started switching power on off immediately...and its relay started making noise...i remove load...after few minutes...a mosfet fried again with a pop sound...and a little transistor 639 started smoking....can u determine what's the exactly problem ???
      Wish u a happy diwali...

      Delete
    3. Hello Nitin, I think the oscillator stage is frozen in your inverter which is causing the mosfets to short circuit through the trafo winding....disconnect the mosfet and the power buffer stage from the board and check whether the oscillator is working or not.

      Delete
    4. Ok sir...i m gonna try it...and let u inform...

      Delete
  31. Hi, Swagatam i have a problem with a 750w modified black&decker inverter if i connect more than 30w it protects itself but the votage doesnt even drop, i already checked the frequencies and they are ok so what are your thoughts for this problem. thanks in advance.

    ReplyDelete
    Replies
    1. Hi Roger, I think the overload protection circuit could be malfunctioning, try to locate the overload cut off relay or the particular circuit section, remove it and then may be you can try troubleshooting the possible fault in it.

      Delete
  32. sir I'm jeylani,
    I'm beginer bt I've interest to learn abt designing of ckts pls guide me

    ReplyDelete
    Replies
    1. Jeylani, you can start posting your specific questions in this blog, I'll reply with solutions...

      Delete

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Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.