# LC filter for pure sine wave inverter

Discussion in 'The Projects Forum' started by lovelyhakeem, Sep 27, 2013.

1. ### lovelyhakeem Thread Starter New Member

Dec 15, 2010
23
0
Dear Members , I have designed pure sine wave inverter using SG3525 and IR2101 . Now at last stage i just want to design LC filter . I have used switching freq 16khz of mosfets . Now i have designed LC filter of this value by using formula , F = 1/(2*PI*SQRT(L*C)), I have used F=50 hz , C=330uF and L = 30.703mH , when i used this filter at outside of Inverter 220 AC , it doesnot work , But if i step down 220V AC to 12 V AC ( using step down transformer ) i got pure sine wave .. Can u plz help me about my mistake and what changes should i make for high voltage . plz , Will be greatly thankful

2. ### donpetru Active Member

Nov 14, 2008
186
25
What type of load (R, L, C) you used on the output LC filter ?
If the load is too small, the voltage drop on the filter inductance is too high and the filter will not function properly. In that case, I recommend you build correctly inductance L.

3. ### lovelyhakeem Thread Starter New Member

Dec 15, 2010
23
0
I have just checked it in no load condition.Can u plz help me to build more correct value lc filter plz

4. ### donpetru Active Member

Nov 14, 2008
186
25
I'll help but to clarify something: you basically built filter or you just theoretically simulated?

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5. ### lovelyhakeem Thread Starter New Member

Dec 15, 2010
23
0
Sir i have built it practically , and checked it under different condition , worked well at low voltage ( 12,13 V ) but not at high voltage , any suggestion ?

6. ### DickCappels Moderator

Aug 21, 2008
2,772
669
This is very weird. Have you measured the peak current and checked to see whether the current rating of the inductor(s) is being exceeded?

7. ### donpetru Active Member

Nov 14, 2008
186
25
An LC filter can behave in a way it does not have load and otherwise if i connect a load (eg., in parallel with the capacitor C).
1. Why voltage capacitor C you chose? For example, 330uF 250VAC or 400VAC or... ?
2. What type of capacitor construction: MKP, MKT ... ?
3. Then, draw exactly how you connected LC filter.
4. Once you have built coil, you measured to see if it has those ~30mH?
Come back with some answers to the questions above.

8. ### lovelyhakeem Thread Starter New Member

Dec 15, 2010
23
0
simple polar capacitor of 330UF and 400 V , Connected in series and measured across Capacitor . I have used built in inductor from market of this value

Nov 14, 2008
186
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10. ### shortbus AAC Fanatic!

Sep 30, 2009
4,095
1,681
I've been following and contributing to the posts by the O/P from the beginning, on his
"pure" sine wave inverter. He hasn't yet shown a schematic for this, he has shown a schematic using a SG3525. This makes a square wave converter. Running a square wave through a transformer, doesn't as far as I've been able to see, make it in to a "pure" sine wave. Before spending a lot of energy on sorting out his problem, you might want to consider this little bit of information.

To LovelyHakeem, you must realize that you have to show your work. A schematic is the language of electronics. Instead of posting a link to another site, why not post it on this site? Makes it easier for everyone.

11. ### Experimentonomen Member

Feb 16, 2011
331
46
You have three threads about literally the same thing and still havent been able to make it work!!

All i can say is this: Scrap the project and go back to school.

Also i feel like the three threads about this should be merged into one.

shortbus likes this.
12. ### RamaD Active Member

Dec 4, 2009
254
33
After going through your many threads, it appears that you have a DC-DC converter of 12V DC - 300V DC, operating at 16kHz., with 3525 pwm controller. This output DC is powering a sinewave inverter controlled by a PIC microcontroller (no schematic or firmware details available). You are designing an LC filter to be used at the output of the inverter.
Can you please clarify as to what do you mean by the filter does not work in high voltage?
For example, no output, output voltage waveform is square and same as input, etc., with values.
What is the voltage & waveform at the input and output of the filter, and also what is the load connected?

13. ### lovelyhakeem Thread Starter New Member

Dec 15, 2010
23
0
Sir i am actually new to this website . Can u plz help me how to shift my all threads to one , at which i can ask my all problems , i am really sorry for it .