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.

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192 comments

comments
Anonymous
March 18, 2012 at 4:11 PM delete

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

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March 18, 2012 at 7:01 PM delete

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

Regards.

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Anonymous
March 19, 2012 at 11:22 AM delete

88AH AUTOMOBILE

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March 19, 2012 at 5:48 PM delete

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.

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Anonymous
March 19, 2012 at 9:52 PM delete

u av d circuit in ur box already

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March 19, 2012 at 10:25 PM delete

which circuit are you referring to?

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Anonymous
March 21, 2012 at 12:56 AM delete

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.

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March 21, 2012 at 8:40 AM delete

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.

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Anonymous
March 21, 2012 at 12:43 PM delete

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

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March 21, 2012 at 3:36 PM delete

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.

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Anonymous
March 22, 2012 at 5:16 AM delete

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

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Anonymous
March 22, 2012 at 5:20 AM delete

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.

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March 22, 2012 at 8:43 AM delete

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

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March 22, 2012 at 8:55 AM delete

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.

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Anonymous
March 22, 2012 at 6:17 PM delete

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

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March 22, 2012 at 6:28 PM delete

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.

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Anonymous
March 23, 2012 at 12:15 PM delete

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

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March 23, 2012 at 4:56 PM delete

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.

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Anonymous
May 12, 2012 at 5:45 AM delete

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

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May 12, 2012 at 10:12 AM delete

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??

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Anonymous
May 13, 2012 at 3:20 AM delete

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.

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November 8, 2012 at 11:33 PM delete

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

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November 9, 2012 at 10:01 AM delete

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.

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December 6, 2012 at 7:14 PM delete

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

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December 7, 2012 at 9:09 AM delete

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.

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January 18, 2013 at 9:02 PM delete

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

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January 19, 2013 at 10:22 AM delete

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

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Diverpico
April 17, 2013 at 1:13 AM delete

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

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April 18, 2013 at 1:11 PM delete

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

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May 4, 2013 at 8:20 PM delete

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

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May 22, 2013 at 4:51 PM delete

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.

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May 22, 2013 at 7:52 PM delete

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

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June 20, 2013 at 1:40 PM delete

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

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June 20, 2013 at 3:39 PM delete

multimeter cannot be used for checking PF, refer to this article for more info:

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

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Anonymous
June 27, 2013 at 9:13 AM delete

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

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June 27, 2013 at 12:51 PM delete

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.

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September 18, 2013 at 2:08 AM delete

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.

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September 18, 2013 at 6:17 PM delete

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

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September 30, 2013 at 7:03 PM delete

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

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September 30, 2013 at 8:36 PM delete

Greetings Steven,

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

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October 2, 2013 at 7:41 AM delete

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.

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October 2, 2013 at 12:39 PM delete

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.

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October 6, 2013 at 6:49 AM delete

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.

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October 6, 2013 at 9:04 PM delete

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

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Anonymous
November 1, 2013 at 2:21 PM delete

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.

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November 2, 2013 at 10:14 AM delete

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

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February 20, 2014 at 3:21 AM delete

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?

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February 20, 2014 at 11:45 AM delete

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.

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February 20, 2014 at 4:59 PM delete

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)!!

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February 21, 2014 at 10:09 AM delete

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.

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April 26, 2014 at 9:39 PM delete

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

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April 27, 2014 at 5:36 PM delete

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.

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May 18, 2014 at 9:48 AM delete

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.

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May 19, 2014 at 10:43 AM delete

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.

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May 23, 2014 at 8:32 AM delete

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

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May 24, 2014 at 9:36 AM delete

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.

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June 13, 2014 at 5:09 AM delete

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?

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June 13, 2014 at 10:53 AM delete

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.

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June 13, 2014 at 10:55 AM delete

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

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July 20, 2014 at 3:25 PM delete

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

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July 21, 2014 at 9:58 AM delete

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.

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July 21, 2014 at 11:12 PM delete

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.

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July 22, 2014 at 3:15 AM delete

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

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July 22, 2014 at 10:35 AM delete

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

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July 22, 2014 at 11:28 AM delete

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..

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October 6, 2014 at 7:10 PM delete

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

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October 7, 2014 at 9:17 AM delete

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

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October 16, 2014 at 8:52 AM delete

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....???

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October 16, 2014 at 8:27 PM delete

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

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October 21, 2014 at 12:22 AM delete

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...

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October 21, 2014 at 11:34 AM delete

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.

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October 21, 2014 at 2:21 PM delete

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

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November 21, 2014 at 2:06 AM delete

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.

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November 21, 2014 at 10:40 AM delete

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.

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December 10, 2014 at 7:26 PM delete

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

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December 12, 2014 at 10:22 AM delete

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

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January 19, 2015 at 9:03 PM delete

Sir Iam B.V.R
I have DC TO AC 200W pwr inverter(12V DC to 220V AC)(50HZ),I wanted to use this by solar pwr,So how much capacity of CCU and BAttery I can use in this circuit

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January 20, 2015 at 8:45 AM delete

Bathula, a 50 AH battery will do the job, however for much longer backup you can opt for a 100 AH or higher batteries.

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April 24, 2015 at 1:00 PM delete

hell sir,
my home inverter doesn't give output. when mains power cutoff, inverter indicates on position but, could't give output. battery rating 12V, 135AH. how can i identify the fault, how to solve the problem or how can i repair.....???

regards
Sushant

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April 24, 2015 at 2:17 PM delete

Hello Sushant,

there are two things which might be causing this problem:

battery power not reaching the inverter, battery not charged or the relay changeovers are faulty and not transferring the relevant power lines across the output

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April 30, 2015 at 7:44 AM delete

Hi! Hope you are doing fine. Can you help me with my power inverter? I have this TBE 1000W power inverter that was working fine until it made this long beeping sound. I removed it from the solar panel system and connected it directly to the battery and it still is making the beeping sound. The battery is fine because it is being used in another solar panel system. What could be the problem? Thanks in advance!

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April 30, 2015 at 2:39 PM delete

Hi, I am sorry it would be very difficult to diagnose or judge an internal fault of a system, because there could be several reasons for a particular faults, not possible without practically checking it.

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May 12, 2015 at 10:33 PM delete

Hi,

I have a Silverline 1000W inverter that made a smell and stopped working!

A visual inspection showed a pin burned and the IC plastic cracked on the SDC 7500 chip.

I was going to solder a DIL socket in and try a new IC but I can't seem to find one online.

Also would you know what sort of fault further downline might have taken this chip out. Its the Vcc pin 12.

It seems to be a difficult IC to source?

Would you have a circuit diagram of this inverter?


Your comments greatly appreciated,


Kev

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May 13, 2015 at 11:56 AM delete

Hi, I compared the pinouts of your inverter IC with a more commonly available IC TL494 and they looked exactly similar.

So I think you can try replacing the burned SDC7500 with a TL494 and check the response.

However I can be difficult to understand or judge the actual reason behind this damage, because normally the supply to the electronic stage is always regulated and through a step down transformer.

I have a simple inverter version which is comparable to the one that you are using, if you have previously built electronic circuits then probably building this one from the start won't be a problem for you, here's the design:

http://www.homemade-circuits.com/2015/05/simplest-pwm-modified-sine-wave.html

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June 21, 2015 at 12:42 PM delete

Hello, could you tell me in 3 lines what is the main difference between repairing inverter and non inverter air condition ? I do not find an easy explanation to tell to someone else. Thank you.

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June 22, 2015 at 9:14 AM delete

An inverter in an air conditioner is used to control the speed of the compressor motor to drive variable refrigerant flow in an air conditioning system to regulate the conditioned-space temperature.

By contrast, traditional air conditioners regulate temperature by using a compressor that is periodically either working at maximum capacity or switched off entirely

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June 30, 2015 at 1:12 PM delete

hi i have an inverter which indicating faulty yet i have replaced all the mosfet with new one what might be the problem pliz assist.

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July 1, 2015 at 5:57 PM delete

without sufficient tips regarding the inverter circuit and the fault it would be difficult to judge the issue...

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July 6, 2015 at 6:31 PM delete

Good day,
I've got a IR series pure sine wave inverter with 48volt system. I only notice this last week where my inverter shows a 9% constant load from 6pm to 6am (night time) even if I turn off all switches in DV box. Thus no electricity flowing yet shows a constant 9% load. Yet before it jump to 9% constant load for night time - the normal load is 1%-3% at 5pm. Any idea what might be causing this. Thank you in advance

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July 7, 2015 at 9:50 AM delete

Although it would be difficult to judge without testing it practically, any circuit that might be associated with the output winding of the inverter transformer could be malfunctioning and leaking power....you can try temporarily removing the connections of the circuit associated wit the output of the trafo and see if the issue rectifies, otherwise it could be something more serious.

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PK
July 7, 2015 at 11:35 AM delete

I am an electrical engineer but not so much into inverter. Your problem made an interesting reading so thought of of understanding it more.
We need to confirm that
1.0 There is no load being fed by circuit not routed through distribution box.
2.0 Confirm the working of indicating meter by using clip on ammeter, before and after 5 PM. Measurement should be done at output wires from inverter to box.
3.0 In case clip reading donot change in correspondence with panel meter, we may doubt problem inside inverter.
4.0 during daytime, switch off all load and confirm meter reading.
These observations may lead us in understanding the problem

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July 19, 2015 at 3:53 PM delete

What would happen if the AC and DC "collide" within the power inverter? The inverter is connected to solar batteries, and it is used as an alternative to power the lighting in our house. But someone turned both the main circuit breaker for the lighting, and the alternative circuit breaker "on". The circuit breaker connected to the power inverter and the solar batteries got "tripped". When i turn off the main circuit breaker and turn on the alternative solar circuit breaker, it is not working. It seems that the power inverter got broken when the two circuit breakers were turned on at the same time. Is there any way to fix the inverter?

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July 20, 2015 at 9:53 AM delete

If DC is connected with a same potential AC, then the during the negative cycle of the AC, their would be an explosion or a short circuit, burning both the DC fuse (if any) and the AC fuse (if any).....if the DC potential is much lower still their would be an explosion and short circuit for both the cycles...if DC potential is much higher still their would be an explosion for both the cycles....but nothing can be confirmed without a practical investigation

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July 20, 2015 at 6:24 PM delete

What do you suggest on doing? Should I change something on my inverter or is it permanently broken and I have to get a new one?

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July 21, 2015 at 9:19 AM delete

if there are any fuses in the middle you can check those whether or not those are burnt and replace them....or check the relevant voltages before the circuit breakers to see if the circuit breaker was the only device which might be damaged and possibly change those with new ones.

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July 22, 2015 at 6:30 AM delete

Sir this anbarasan iam interesting to service inverter i already sent my request but no response once again i request in 850va inverter mosfet explide after change mosfet abnormal heat produce in the mosfet heatsink is there driver problem please reply me

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July 22, 2015 at 2:34 PM delete

I have already answered to your earlier comment, you can find it in this article:

http://www.homemade-circuits.com/2012/04/how-to-check-mosfet-using-digital.html?showComment=1437282049692#c5075736144765103392


inverter is a huge subject, it cannot be learned by just referring to a diagram or an article, you should learn it through an institute

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July 30, 2015 at 2:23 PM delete

hi can you know the replacement of this chip ic( 1203 LNK36GN OE245B ) it was blown and no available on electronic stores

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July 31, 2015 at 4:57 PM delete

sorry I could not find any info regarding it, online

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August 4, 2015 at 7:08 PM delete

hi my inverter is only putting out 185 volts why is that( 16 batteries connected)

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August 6, 2015 at 4:53 PM delete

Hi Swagatam, I have an inverter ( 300W Meind ) which short circuits when I give power to it to power on. When there is no fuse, it doesn't do that. When the switch is ON, it trys to BEEP for low power.

It had a blown capacitor which I replaced it with a higher vlotage. ( 16 to 25 )

There are no blown or burnt components.

Please help me, I don't want to spend more money on buying another inverter.

Thanks!

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August 7, 2015 at 1:55 PM delete

Hi Parsa,

I am sorry, it would be impossible to judge the fault without practically checking it.

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August 17, 2015 at 9:14 PM delete

I have a 2200W inverter to provide back up power for a sump pump. The inverter goes into overload (and blows an inline 15A 125V fuse) every time anything is plugged into the output plug.

This particular inverter is designed to plug into wall AC to keep the batteries charged and pass through 'wall' power when it is available. When power goes out it switches to battery power and inverter mode to power my sump pump.

Whether the unit is passing through 'wall power' or in 'inverter' mode as soon as anything is plugged into the ouput outlets there is a 'buzzing' / 'vibraton' and an overload condition. It seems like there is a short occurring when anything is plugged into the outlet.

What could be the problem? I am not sure where to look for the shorted condition ... transformer? Why would it only short when something is plugged in... and why would it short when passing through current from the wall as well as when producing inverted power from the batteries?

Note - this unit used to function normally.... so it must be a worn or failed part / condition.

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August 18, 2015 at 12:40 PM delete

I think some internal circuit stage might be malfunctioning and shorting the output possibly through a relay, on detection of a load.

You can troubleshoot it by tracking and locating the "load" wires which may be terminating from the trafo output, and temporarily disconnect everything that might be associated with these wires....after doing this you could check whether the problems persists or not...if still it continues to behave in the same manner then the problem could be assumed to be on the primary side....

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August 20, 2015 at 10:10 PM delete

Hello good sir,

I have a 300W 12 V DC to 230 V AC Mascot Inverter in my boat, which supplies a tv-screen and an underwater camera. The problem is that most times the screen will not turn on, it just makes a ticking sound. But when I pull the plug and wait a couple of minutes with the engine running, it will usually start when I plug it in again..

I measured the inverter inlet and it says 16 V, and the outlet is only around 190 Volts. Should it not be around 230 Volts? I have a 12 V 125 AH battery. I'm a rookie when it comes to electronics, so I hope you'll have an idea whats going on.. :]

Regards

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August 21, 2015 at 9:58 AM delete

Hello Nozthis,

It could be due to insufficient initial current for the inverter to start the load...you can put a switch in series with the load, and initially keep it switched OFF....you can switch it ON once the inverter and the engine has gathered enough strength.....or alternatively you can upgrade the battery with a higher AH rated battery.

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August 21, 2015 at 9:59 AM delete

...the drop in the voltage could be due to insufficient current from the battery

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August 24, 2015 at 6:11 PM delete

Hello Sir Swagatam,
My inverter was affected by a thunder strike. It can still be powered on when the power cable is plugged. The heat sink is observed to heat up when power is being supplied but the inverter does not function anymore as before. The capacitor at the end near the power supply line is tested with a multi-meter and seen to be ok. There are no visibly burnt components on the panel (motherboard) when closely inspected. How do I fix this problem?

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August 24, 2015 at 9:56 PM delete

Hello Chinda,

It would be extremely difficult to judge the fault from here, because s thunder lightning can be so powerful that even if it brushes-of an electronic circuit, the small sensitive devices could get damaged permanently without getting burnt.

It wouldn't be a wise idea to speculate without practically checking it.

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August 30, 2015 at 6:48 PM delete

Hello Mr.Swagatam
I have 500w inverter which I use with car battery and by mistake I placed the positive (catch) with the negitive bettery output and placed the negative (catch) with the positive bettery output
Since then the inverter is not working.
I wonder whats the problem and how do I fix it?

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September 6, 2015 at 5:41 PM delete

Swagatam Sir, Good Evening :)

I have luminous inverter UPS LB 800 VA and been using it for last 7 years. Now it doest not charge battery althogh smart charging LED blinks. smart charging LED remains blinking despite main power cut. Battery is functional as other inverter charges it well.
Sir your immediate reply is solicited and thanking you in advance.

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September 7, 2015 at 9:41 AM delete

Hi Amar,

you can check the voltage across the charging output points, and also the current available from it.

voltage can be checked using a multimeter on DC V range, while the current can be checked by selecting the DC 10 Amp slot or the highest amp range in the meter,

If the output is absent or is too low you can assume something's not correct in the circuit or may be the output power device is blown.

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September 15, 2015 at 6:48 PM delete

Hi Swagatam, My inverter shows battery low in 10 mins time, I have checked the distilled water in the battery and filled it. I worked fine for 2 days and back to the same. What should I do ?

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September 16, 2015 at 11:30 AM delete

Hi Dan,

is your battery too old? anyway you can confirm the condition of the battery by removing it from the inverter and by checking it with an appropriate load, if it shows quick discharging symptom or if it shows sluggish response while getting charged you can assume it to be dead or in a bad condition....

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September 16, 2015 at 4:50 PM delete

Im just a kid don't know much about electronics. The thing is my inverter fuse keeps blowing up in seconds after changing it to more powerful ones. What can i do? The input voltage isnt high. Its usually around 220v

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September 17, 2015 at 8:09 PM delete

sorry, it would be difficult to judge the fault without a practical look....may be you'll be able to trace it someday once you have grown up and learned adequately about electronics....

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September 22, 2015 at 3:55 PM delete

please guide me the difference between narrow and wide switch function?

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September 23, 2015 at 8:53 AM delete

couldn't understand your question....

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October 13, 2015 at 10:41 AM delete

hi sir m using microtek 800 va ups its not giving back up out put.i hv checked out put winding of transformer.the windings are ok but showing no supply.please tell me probable fault.

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October 13, 2015 at 5:05 PM delete

Hi Satyendra, the fault could be hidden in the circuit board section and difficult to judge without a practical assessment, so I am sorry it won't be feasible to detect without checking.

One common reason could be a blown fuse, or a burnt wire...you can check for these.

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PK
October 13, 2015 at 5:13 PM delete

The 800 VA inverter has 40A orange coloured fuses on the board. Please check these four fuses for integrity. These are located on board.
Also check that toggle switch for vacations is not in off position. If it is in off then LCD display shows trikle charging by flickering filling nozzle.
Please check that battery is healthy
Also ensure that inverter has s switched on as indicated by small green LED.

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October 25, 2015 at 11:04 PM delete

Good day, sir.
I have a Coleman Inverter PMP3000. I made a mistake when I connected on a reversed polarity. All fuses are busted. I changed all the fuses with new ones but when I connected it again with the right polarity, all the fuses got busted again. What is likely the cause of the busting of fuses? Please advise. Thank you very much. God bless.

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October 26, 2015 at 9:04 AM delete

Good day benz, it's surprising that your inverter did not have a reverse polarity protection, anyway now it seems it's been damaged quite a lot, and the internal power devices could be burnt.... you'll need to open it completely and check the power devices using a multimeter.

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October 26, 2015 at 8:39 PM delete

Thank you very much for your reply,sir. Yes, it has no reversed polarity protection;
I opened it and so far my ocular inspection shows NO sign of burnt out power devices, resistors, capacitors,etc. Looks clean and net in all its parts. I haven't used the multimeter as I give this feedback, I'll complete first ,then I'll inform you. Thanks again,sir.

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October 27, 2015 at 11:08 AM delete

thanks Benz, electronics can never be confirmed with mere eye inspection :), you'll need a multimeter for this...fuse blowing off even when connected correctly indicates that the output devices are most probably burnt or shorted.

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October 28, 2015 at 7:21 AM delete

Good evening sir,
I have a Schumacher 1500 watt inverter that was mistakenly connected to the 12 volt battery backwards ( + to -) and (- to +). There was an audible pop sound and then nothing. After connecting properly still no response. From your experience is this likely to be repairable? I have very limited experience or knowledge on the subject but I'd like to know if there is a chance of repair.
Thanks,
Randy

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October 28, 2015 at 11:26 AM delete

Hi Randy, your inverter problem appears to be similar to Benz's inverter problem....it's really surprising how the manufacturers missed the reverse polarity protection, which is extremely important in such equipment which require external battery connection.

anyway, the problem is definitely repairable.

you could probably follow the positive line and check the stages which are being connected with this line.

Most probably you would find this line going to the PCB of the inverter which might be having many associated ICs and other devices...so you could check whether these ICs are directly involved with the positive line or not, if yes, then it would imply that these devices could have been damaged due to the wrong battery connection.

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November 1, 2015 at 6:13 PM delete

Dear sir,
I am using micortek EB 850 inverter gor last 4-5 years. Today I found Mains to UPS mode is not working. In mains power supply mode displaying full charge (New battery just 2 months old) battery in display, Once main power supply is off, all display light off in inverter, and no power output also.
I have checked the fuse, it is OK.
I have checked there is no loose connection also.
Please help.

Thanks & regards,
Suman Rana

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November 2, 2015 at 9:36 AM delete

Dear Suman,

The problem could be in the change-over driver section which could be operating through relays or mosfets or IGBTs...this section might not be transferring or switching in response to the detected power failure.

so this section will need to be traced and troubleshooted, perhaps one of the driver transistor could have gone faulty.

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November 10, 2015 at 8:33 PM delete

Dear Sir,

I have a 5000w power inverter. When you switch to inverter use, it begins to beep although battery is not weak. When you turn on the charging unit to charge battery, it beeps as well. What could be the cause and how can this be fixed.

Thank you.

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November 11, 2015 at 10:53 AM delete

Dear Nikki,

It would be difficult to locate the exact fault without a practical check up, but broadly it could be due to a faulty part in the low battery sensor circuit stage or a bad solder point in this stage

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November 21, 2015 at 2:33 AM delete

Dear Sawagatam,my UPS Infosec x3 2000 one side 4 FET burnt. I replaced all four. Opposite side all four ok. But still UPS not works and display shows 0 with continous beep.

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November 21, 2015 at 10:04 AM delete

I am sorry Ali, it would be difficult to judge the issue by imagining, it'll need to be diagnosed practically

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November 21, 2015 at 11:56 AM delete

Thanks for the quick reply Brother ! i would like ask for learning and understanding in this UPS. four FET one side and four FET opposite side, In each side 2 FET are insulated with layer with heat sink and other two each side without insulated layer piece.what is the logic? And battery charging how happens? with which rectified dc voltage and from where?

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November 21, 2015 at 6:49 PM delete

Dear ali, again it would be difficult to judge unless and until it's actually and traced from top to bottom because inverter circuits come in many different varieties with specific configurations, so all have their own exclusive design and operational methods

......for the battery charging your UPS must be deriving the input from your mains AC, even if a transformer is not included it could through an SMPS circuit stage.

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November 27, 2015 at 9:38 AM delete

Hello Swagatam. I have a 2.4kva (24v) inverter system with 2 batteries of 12 v (100A) each. I have noticed recently that after a full charge, the low battery alarm comes on in like 5mins but power may stay up to 7hours with the alarm. Please kindly advise.

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November 28, 2015 at 8:52 AM delete

Hello bassey,

I think the low voltage detector stage has gone faulty or the preset adjustment could have been affected or the preset itself has become faulty...you may check for one of these issues.

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November 30, 2015 at 9:06 AM delete

Hello Swagatam,

I have a Hyundai 3.4kw inverter generator (HY3600SEI). The generator engine starts first time and runs up to speed. The green AC ready light comes on for about 3 seconds and then go's off (power is removed from output socket) and the Red overload light comes on and stays on.

If I apply a load (any size load up to 3400 watts) within the 3 second time frame that the generator starts and energizes with green light (Power available), the load will power up and run for hours producing power. If no load is applied, red light comes on and power is no longer available without turning off engine and restarting.

Any idea's?

Thanks
Warren

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November 30, 2015 at 3:58 PM delete

Hello Warren, it appears like the inverter is equipped with a "no load cut-off" feature and that's a good feature to be included in the system.

I think you should keep the load connected initially and switch ON the inverter in this position to bypass the concerned feature?

and possibly connecting 3400 watts may not be crucial, you can try with a 100 or 20 watt load and check the response., it should do the trick.

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December 3, 2015 at 1:30 PM delete

Hello Swagatam,
i have been following the conversations you have had with different people with different questions, i am really impressed with your intelligence and willingness to help other people, thanks.
However i have my own problem which believe you will help.
My inveter is 500 watts and i use it for only the TV which is 100 warts and 3 energy saver bulb 12 watts each. Now my inverter is working but the green light is off and the voltage gauge is down, what could be the problem and what are the dangers if possible any suggestions for fixing the issue?

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December 3, 2015 at 1:33 PM delete

Hello Swagatam,
In connection with the question i asked, i am using the battery i am using is 12 V and it is 100AH

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December 3, 2015 at 8:23 PM delete

Thank you Joseph, the pleasure is all mine:)

If your inverter's power output related operations are normal, then the failure of the indicators cannot be considered as a critical issue....it could be simply due to a damaged part or so in the indicator circuit stage which might be affecting its working....you can check the specific stage and change the faulty part after locating it correctly that will hopefully solve the problem for you....

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December 8, 2015 at 1:56 PM delete

my inverter is showing a short circuit warning. i have checked all mosfets. they are in good condition. what might be the reason. can u help me about the common circuits for shortcircuit detection or help me to find the damaged component

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December 9, 2015 at 8:34 AM delete

try disconnecting the wires that are terminating to the transformer from the mosfets and check the response....you can also try connecting an ammeter in series with the battery positive and check the current....if it's high at switch ON would indicate a short, or else the warning could be assumed to be a false or malfunctioning.

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December 21, 2015 at 2:28 AM delete

hi Swagatam I have an inverter that just installed in my car and with direct connect to the battery with aligator clips. when I plug in a small 230V radio in the inverter. the radio comes on and then goes off again constantly. I know it is not a faulty radio. it works in a normal house plug. Do you have any suggestions on this?

Thanks

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December 21, 2015 at 6:26 PM delete

Hi Nik, the problem could be due to the very small load presented by the radio, which is prompting the inverter's "no load shut off" feature to activate....try using a 100 watt bulb and see whether the issue still persists.

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December 26, 2015 at 3:48 AM delete

Hi
I have suoer inverter 2000W the output is 219 vac but the fan is not working. what is the problem????

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December 26, 2015 at 6:56 PM delete

Hi, check the voltage across the fan wires, if it's OK then the fan could be faulty, otherwise the circuit which is responsible for producing the voltage could be faulty.

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January 5, 2016 at 3:42 PM delete

Hello sir.i have a ups Lebanon make.3700va,.it's now beeping n indicating inverter off/charger on from time to time.what might be the problem n what's the remedy for that.?
Thanks in advance.

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January 5, 2016 at 4:56 PM delete

Hello Jack, the "mains to INV" changeover relay stage could be malfunctioning, open the inverter and check the relay stage which is responsible for implementing this changeover, and check the transistors or the IC associated with the relay switching action.

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January 5, 2016 at 4:57 PM delete

or may be your battery has become defective, check the response by replacing it with a fully charged new battery

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January 12, 2016 at 5:29 AM delete

Hi Sir, if I charge my phone and iPad this does not happen but the moment I put on my 120w TV my 900va Indian inverter based on MOSFET technology trips into Low battery with alarm and goes back instantly to invert and power the TV.

Sometimes I will have to off and on the inverter a few times before it works. What could please be the issue, is it the inverter or battery as battery reads between 11v - 13.5v

Thanks in anticipation.

BILLY

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January 12, 2016 at 5:43 AM delete

Hi Sir, My inverter goes into Low Battery modend instantly goes back to normal inverting when I put on my 120watt TV. Sometimes it will go into Low Battery and will not recover until I off the inverter and on again. Meanwhile my battery still reads 11v - 13.5v and when it works, it gives me backup up to 14 hours.

Can it be the inverter or the battery that has problem? Kindly assist.

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January 12, 2016 at 11:24 AM delete

Hi Billy, It will be difficult to pin-point the fault but surely it's around the "battery level detector" stage....could be a bad solder point on the IC leads, you can check it and re-solder the points and check the response.

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January 19, 2016 at 4:19 PM delete

hello sir,
i've 850 su kam inverter. its problem is that it does not charge batter when mains is on and when it is in inverter on mode it doesn't shows mains. also when mains is 220 volts the inverter outputs is just 96v. again on inverter mode the output is 220volts
i changed the relay...but problem is same
plz reply me

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January 20, 2016 at 7:38 AM delete

Hello Amit, it looks like there's some kind of loose connection in the wiring, check all the connectors especially the wires which are coming from the transformer to the output socket, and also the connections between the relay and the transformer.

Clean the PCB with a brush and check if all the solder points near the changeover relay are fine.

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January 27, 2016 at 10:21 AM delete

swagatam sir..... microtek sine wave inverter shows over load on load n keeps on buzzing ... i changeD the relay the connecteions were damaged ... still ot shows over load on no load n keeps on buzzing.... is that the function ic problem or else??

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January 27, 2016 at 6:30 PM delete

Aqib, try checking the stage which is responsible for activating the relay, it could be an opamp which is configured to sense overload and could have gone faulty and might be causing the relay to trip...therefore locate this opamp or whatsoever stage it may be and check the reason behind its malfunctioning, and possibly replace the faulty part with a new one....

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February 3, 2016 at 6:57 AM delete

Good Morning Sir,

I have recieved a lebanon made inverter to repair that has one transfo (used for both charging and DC-AC ivertion), Six mosfet (IRFP250n) each three are in parallel, Inverter board, A big relay close to the transfo and Battery charging ciecuit.
The inverter is not working. I check it following the guidlines you provided above and I found out that, the inverter can work when 220 AC power applied to it but it cannot work on battery.


The foulties area are summarised bellow..

1. It cannot charge the battery while the transformer has provided the DC voltage through the help of the Big relay.

2. If battery is connected, a relay on battery charging board is moving.

3. Also, there are two big resistor of about 10 or 15watts connected in parallel that spilt into pieces (unfortunatelly it has no details on it, I would have change it and try the inverter) but, when I arranged it and apply AC power I can see the charging LED lighting. But to me, I think this resistors are what prevent inverter to accept the battery, because they are working as a trigger.

1) Sir could you please suggest what is wrong?
2) And, what type of the resistors should I try?

Thank you Sir.

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February 3, 2016 at 11:00 AM delete

Aminu, it will be extremely difficult to judge the faults without a practical check up...so I won't be able suggest much.

for the resistors, you can replace them with 12V flashlight bulbs and check the response for the time being, if it works then you can experiment with may be a 100 ohm resistor initially, and see its effect on the performance.... and modify the value accordingly.

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February 6, 2016 at 3:26 AM delete

Sir,
I did not find the 100 ohms, but I found a pair of 300 ohms 20watts and 330 ohms 10watts.I connected each pairs in parallel and I tried each but the pair of reaistors are getting too much hot and smoky. If I leave it for some time, It charge the battery.

Sir is there some solutions?

thank you very much.

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February 6, 2016 at 11:27 AM delete

Aminu, disconnect the battery and then check whether the resistor becomes hot or not, if yes then it's not correct and might need further investigation, if the heating stops then you are probably in the right direction, and can try checking the path of these resistors up to the battery and assess the cause of the heating up of the resistors.

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February 6, 2016 at 12:33 PM delete

Yes sir, the resistors are getting hot only if I connected the battery.

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February 8, 2016 at 8:12 AM delete

My inverter trips with overload indicator coming on when power fails, it continues in this condition even when all load is disConnected and the inverter is reset. But strangely, functions well if I disconnect it from the mains and reset it even with full load connected.

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February 8, 2016 at 4:42 PM delete

there could be a related capacitor which could be linked with the mains supply and stays charged keeping the over load cut-off latched, as soon as the mans is removed this capacitor could be discharging and releasing the latch.

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February 10, 2016 at 1:46 AM delete

Please help me .whare can i find dspic inverter voltage datagram

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February 10, 2016 at 4:37 PM delete

Sir, but the overload tripping returns if the input is connected to main while no power supply is coming from the supply company

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February 10, 2016 at 5:28 PM delete

Sir, but the overload tripping returns if the input is connected to main while no power supply is coming from the supply company. Also, the overload happens only if the supply company stops the supply, turning the mains off does not cause tripping.

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February 11, 2016 at 9:25 AM delete

then it could be difficult to assess the fault because it appears that the neutral line of the mains is involved with the inverter operation, and connecting the plug could be connecting the neutral with the inverter and causing the issue...you may have to call a technician for a practical check up

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February 11, 2016 at 9:34 AM delete

I think the neutral line is somehow involved with the issue...

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February 22, 2016 at 4:00 AM delete

Sir,i have a 1.5kva inverter.My inverter shows short circuit on the dashboard but I have changed all the mosfets and even capactiors.i noticed that only 4 mosfts get hot on powers the inverter out of the 8 mosfets used.what could be thhe problem? thanks

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February 22, 2016 at 11:48 AM delete

Kenn, connect 12V car bulbs in series between transformer taps and the mosfet drains...and check whether the brightness is equal on the bulbs or not....if not then probably trafo could be damaged or malfunctioning...or may be the oscillator is not providing identical frequency across the mosfets...or there could some other hidden aspect which you can diagnose sing a DMM.

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February 22, 2016 at 3:39 PM delete

Thanks for ur prompt response.The brightness varies on the mosfets,also on isolation of the transformer,i still get the shortcircuit error on the dashboard.i cant see any physically damaged device,how do I find d oscialltor circuit & anyother means of troubleshooting it?
thanks

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February 22, 2016 at 8:30 PM delete

If the short is showing even after disconnecting the transformer then I think the problem could be somewhere in the mosfet stage....you could try removing the whole mosfet stage and check the situation again by switching ON power....

the frequency could be checked at the source which connects with the gates of the mosfets...you can use your DMM's frequency range for measuring the same.

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February 23, 2016 at 11:50 AM delete

i have removed the whole mosfet stagge including the drivers (Ir2110) but when I switch on I still get Short circuit on the dashboard.It really looks like a complex situation...Any Ideas?

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February 24, 2016 at 9:31 AM delete

since you have disconnected the whole circuit now it should be much easier to find the shorting locating, you can do it by using a multimeter or by connecting a series bulb with the input and then by disconnecting the remaining stages one by one until the bulb switches OFF.

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March 12, 2016 at 1:08 PM delete

i am repairing a invertec v270, i already replace the open capacitors with a new one. checked the fuse, diodes resistors and transistor but still there is no input.

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March 12, 2016 at 8:51 PM delete

sorry, that would be difficult to judge without seeing

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March 13, 2016 at 3:36 PM delete

i am having o-general inverter split air-conditioner two year the outdoor timer board was
faulty, i am changed. it is working for past two years.now i am got fault the timer board.
the indoor unit blink two times means , the o-general enginneers says, the outdoor timer to be changed.they says. how the timer board will get frequentlyfaulty?
.

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March 14, 2016 at 8:32 AM delete

2 years is quite a long period of time and things can get faulty within this period, change it once more and this time tell the engineers to show you what exactly they are changing and also confirm the operating parameters of the unit....and do not give them the old module....keep it with you and check it afterwards whether it was really faulty.

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March 16, 2016 at 4:16 PM delete

Hi swagatam
I have a sukam 750va inverter. for the last few days its giving unique problem whenever i connect only a ups through it, ups starts giving fast tic tic sound of relay and when i connect it to a power point which isn't through inverter, it works fine. and when i switch on a tubelight or a fan ups' relay tic tic sound instantly stops. what could be the possible reason . i have measured voltages through and without inverter it's almost same. however when i measured dc voltage which charges the battery it was 13.9v instead of 12. please help me in this ... thanks

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March 17, 2016 at 9:31 AM delete

Hi Suresh, it will be difficult to understand the issue without checking it practically....but the 13.9V is not bad, it's correct for charging the battery.

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March 22, 2016 at 4:24 PM delete

Hi, I've a sine wave 2000W inverter. It has started showing bt in its display. What could be the possibility? I'm unable to get any help right now.

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March 23, 2016 at 2:17 AM delete

Hi my name is ganesh , I am using luminiuos inverter 800 VA with sukum tubular batteries 150 Ah , I have been using this inverter for more than 6 years and the battery about 2 years ,before few days when the power went off the inverter started with a sound usually I use my system in inverter but this time it got restarted and the fan rotated in a very low speed with a huge sound then I off my system and checked now the fan speed was there but there was an humming noise from the fan,also the same noise with a vibration in the inverter ... Can anyone tell me what's happening any problem with connections or problem in inverter what should I do

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March 23, 2016 at 7:16 AM delete

Sorry, it would be difficult to diagnose without a practical testing.

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March 24, 2016 at 10:30 AM delete

The problem could be with your fan and or with your inverter, most probably it could be with your inverter....I think the output harmonic filter circuit might be malfunctioning, an involved capacitor might have gone short or faulty.

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