inverter modified sine wave not work

[erchiu]

Hi every one
Hoping to be helpful to other users, I redesigned the circuit following step by step the tracks of my inverter.
I found many differences from the diagram taken from web.
Now you can understand better.
Thanks for any help.

 

[Audioguru]

Your schematic was saved as a very fuzzy JPG file type instead of saved as a very clear PNG file type.

 

[erchiu]

I'm sorry but the source was already ' blurry .
I just redesigned the circuit properly , as my inverter .
erchiu

 

[erchiu]

Ok, i found the resistor R32 broken, i have replaced it and the second stage started to work.
With my instrument i read 216 vac in output, but on the capacitors after the rectifier bridge i have now only 250vdc and with my scope i see an perfect modified sine wave but with 250volts of peak.
Should not be about 310 volts?
Thank you so much to everyone

 

[kabeer02]

you can adjust your voltage from DC-DC converter stage

 

[erchiu]

Hi kabeer02,
Can you suggest how do?
thanks

 

[kabeer02]

your schematic diagram is not clear but changing the ref voltage at pin1 or 2 of TL494 will lead to change of the duty-cycle of the pulse and therefore changing the output voltage

 

[erchiu]

Forgive me,
but do you mean pins 1 and 2 of the second TL494 right?
how can I do to make the photo more clear?
thank you

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this is the diagram saved in jpeg format


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note: the VR on diagram is from 100k instead 10k

 

[Audioguru]

how can I do to make the photo more clear?

You saved the schematic as a JPG file type that is very fuzzy. Instead you should save it as a PNG, GIF or PDF file type that is very clear.

- - - Updated - - -

how can I do to make the photo more clear?

You saved the schematic as a JPG file type that is very fuzzy. Instead you should save it as a PNG, GIF or PDF file type that is very clear.

- - - Updated - - -

Why does this website take forever to post something then it says, "Do you want to leave this page? Do you want to stay on this page?" Then another long delay and it shows the post is duplicated.

 

[chemelec]

Forgive me,
but do you mean pins 1 and 2 of the second TL494 right?
how can I do to make the photo more clear?
thank you

- - - Updated - - -

this is the diagram saved in jpeg format


- - - Updated - - -

note: the VR on diagram is from 100k instead 10k

Scan it in Black and White and save it as a TIF or PNG File.
Usually Much Better Detail.

You Can't save Black and White in JPG, it will convert to Gray Scale.
Only a Gray Scale or Color saves in JPG.

 

[BradtheRad]

Why does this website take forever to post something then it says, "Do you want to leave this page? Do you want to stay on this page?" Then another long delay and it shows the post is duplicated.

The same thing happens to me every 15 or 20 times I post. Might not happen for weeks, then it crops up.

I've had it a few times in the past week. No hint as to the cause.

Often, if I click 'cancel', then close the page, then come back to it, I see my message did get posted.

 

[erchiu]

Sorry if I insist , but the digraph that I found on the internet was in gif ( about 100kb ) .
I have changed to " paint" to make it equal to my inverter .
I do not have many programs to optimize this file . Can I somehow with "paint " to make it more ' clear?
Thanks again to all .
Erchiu

 

[kabeer02]

Not the second TL494 the first that control the DC-DC converter stage

 

[erchiu]

thank you,
between pins 14 and 15, there is an variable resistor (it is from 100k, instead 10k my error)
can be it to set?

 

[kabeer02]

yes you can set it and see the effect at the output DC voltage

 

[Audioguru]

If the original GIF image is fuzzy then Paint program cannot make it look much better. Saving it in JPG will add the many little dots around text and line junctions.
Here is a closeup look at what saving a clear schematic as a JPG file type does to a schematic:

 

[erchiu]

i tryed to set the variable resistor (100k) , doing it 10 turn to right and 10 turn to left, but the voltage on capacitors is always the same 240 vdc and the peak of the wave form in output is 240 volt.




the wave form as you see from picture is perfect (i guess).


do you have some ideas what i can do to check still.
i measured the output voltage with a tester in AC position and i read 216 VAC.


meanwhile i am searching to clear up the diagram the more possible.
thank you so much
erchiu

 

[BradtheRad]

i measured the output voltage with a tester in AC position and i read 216 VAC.

I too got unexpected low AC volt readings on my meters, when I hooked them up to my modified sine wave inverter. My inverter was working fine. However it is because the meters are calibrated to measure sinewaves, not square-ish waveforms.

the peak of the wave form in output is 240 volt.

the wave form as you see from picture is perfect (i guess).

It is not bad. I imagine the waveform remained a longer time at 0V, when the inverter was new. But you have success now, compared to having an inverter that's not working at all.

You have 240V peak on a square-ish wave. This carries approximately the same power as a sine wave with peaks of 330 V.

 

[erchiu]

thank you bradtherad,

so, i can to consider the inverter repaired.

in this moment, there are only 4 mosfets of final stage (instead 8 mosfets), and without heatsink and i tryed the inverter only with little load (led ligth 10w).

the light and 'lit.

as soon as i will have others mosfet, i will try with a major load.

thank you so much everyone
erchiu