Pure sin wave inverter

[--BawA--]

i have made an inverter using linear topology ,12vdc to 220vac 100va ,,but it produce square wave of 50hz,, i want to know how to convert this square wave into pure sine wave (using reference sine wave),,please help me ,,i have searched on internet alot,but didn't find any useful data...

 

[barry]

That's not easy. How 'pure'? You could use a 50Hz low-pass filter.

 

[Tahmid]

i have made an inverter using linear topology ,12vdc to 220vac 100va ,,but it produce square wave of 50hz,, i want to know how to convert this square wave into pure sine wave (using reference sine wave),,please help me ,,i have searched on internet alot,but didn't find any useful data...

You will have very poor efficiency (very high losses) if you do manage convert the square wave output to sine wave using some sort of filter.

It's better if you can redesign your circuit using sinusoidal pulse width modulation (SPWM).

 

[barry]

You will have very poor efficiency (very high losses) if you do manage convert the square wave output to sine wave using some sort of filter.

It's better if you can redesign your circuit using sinusoidal pulse width modulation (SPWM).

Agreed. As I said, it's pretty difficult to turn a square into a sine. Think of it this way: your square wave has a fundamental (50Hz) sine wave, along with a bunch of harmonics. If you discard/filter those harmonics, you are throwing away the energy contained in those harmonics.

 

[Tahmid]

Think of it in your context. You're making the inverter to provide energy to the load. But if you manage to filter the square wave into the sine wave, you're throwing away energy, whereas your requirement is energy for the load.

A design using SPWM can give you quite high efficiency. You should go through existing threads on edaboard where you can find loads of information. And there's always Google. Of course, you'd need to be able to program and use microcontrollers. If not, you can still make a sine wave inverter without microcontroller.

You might find these interesting:
https://www.wpi.edu/Pubs/E-project/Available/E-project-042507-092653/unrestricted/MQP_D_1_2.pdf
https://www.wpi.edu/Pubs/E-project/...-190851/unrestricted/PWM_Techniques_final.pdf

 

[BradtheRad]

This method is interesting to imagine how it could work, whether or not it will work with the existing inverter components.
It could be easier than constructing a new inverter.

Using tuned coil and capacitor to turn square waves into sine waves.



The coil and capacitor values have to be chosen so their reactance is the same as load impedance, at the frequency of operation.

If the load is changed, then the coil and capacitor must also be changed.

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They are not exactly sine waves...

However I have seen by using other values for the coil and capacitor, a closer resemblance to sine waves.

I did not post that schematic. It generated voltage swings which appeared to contradict the laws of physics.

 

[--BawA--]

Thanks tahmid ..can u plzz tell me in detail (with schematics )of smps based inverter and also about spwm technique to get sine wave..I hve visited your blog and tried to contact u but didn't find ur email id ...please help me ..I will be very thankful to u ..

 

[tpetar]

You can search EDABoard for existing threads, use search field in upper right corner "pure sine wave inverter".

 

[Tahmid]

This link that I provided in my above post is a complete project: https://www.wpi.edu/Pubs/E-project/Available/E-project-042507-092653/unrestricted/MQP_D_1_2.pdf

If you haven't already, go through these:
https://tahmidmc.blogspot.com/2011/01/generation-and-implementation-of-sine.html

https://www.edaboard.com/blog/1798/
https://www.edaboard.com/blog/1800/
https://www.edaboard.com/blog/1803/

Hope this helps.
Tahmid.

 

[--BawA--]

Thanks again tahmid ...plzz clear my this confusion too
Suppose I have generated 300 vdc and also 50 hz reference sine wave ..now my aim is to convert this 311vdc to 220vac sine wave..u hve said that this 50 hz sine will go to full bridge and 311 vdc will convert to 220 vac..please tell me that how this full bridge circuit will convert 311vdc to 220vac using
50hZ reference sine wave...and also the role of spwm ...

 

[Tahmid]

220 VRMS has a peak of 220V * √2 = 311V.

So, when you convert from DC to sine wave, DC bus voltage is the peak voltage (assuming "100% duty cycle"). So, for 220VAC output, DC bus voltage should be 311V. Theoretically. Practically, you must use a slightly higher voltage to compensate for the losses.

SPWM is short for sinusoidal pulse width modulation. It is used to generate the sine wave approximation digitally by using square waves. When this is filtered using an LC filter, you get a sine wave output. It is used to drive the MOSFETs using square waves and to get a sine wave output. In most cases, it will be generated using a microcontroller. In inverters in Bangladesh and India, the most common microcontroller used for this purpose is the 16F72. Other microcontrollers are used too.

Hope this helps.
Tahmid.

 

[--BawA--]

thanx again tahmid,,if u don't mind ,plzz tell me how to give this spwm signal to full bridge configuration,,,also give me schematics and working of full bridge to convert 311 vdc to 220vac sine wave,,and also tell me about the sine table in detail ,,plzz

 

[Tahmid]

How to apply SPWM + Sine table in detail: https://tahmidmc.blogspot.com/2011/01/generation-and-implementation-of-sine.html

Practical Implementation: https://www.edaboard.com/blog/1800/

Please go through the above documents first. You will get the answers to your questions. If you have any queries after reading the above documents, then ask and I'll be glad to answer. :smile:

 

[--BawA--]

Thanx tahmid ... very few people in the world are like you......you way of helping others inspires the youth generation....thanx alot...

 

[tpetar]

Mathematical Manipulation of Pure Sine Wave Inverter Using Atmel 89S2051
**broken link removed**

 

[--BawA--]

thanx tpetar,,,
plzz tell me the mechanism of driving the mosfet gate through spwm,,,i mean ,by switching the mosfet in time domain ,how can we get sine wave output ,,,? suppose i have a square wave of 50 hz and i give this wave to mosfet gate then inside mosfet channel will be formed between drain and source at the rate of 50hz(alternatvily 20ms i.e 10ms channel will be formed and 10 millisecond channel will be empty) so by doing this we can get a squre wave output,,,i want to know than how this spwm do this ,,n also help me about spwm,,,,

 

[tpetar]

With filtering get pure sine wave. See PDF in post #15.

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Also you can see this document:

http://www.wpi.edu/Pubs/E-project/Available/E-project-042711-190851/unrestricted/PWM_Techniques_final.pdf

 

[--BawA--]

thanx alot tpetar ,,,
i need one more help,,,plz send me schematics of smps based inverter (>500 watt) with component list ,,,,

 

[tpetar]

thanx alot tpetar ,,,
i need one more help,,,plz send me schematics of smps based inverter (>500 watt) with component list ,,,,

At the beginning that you turn your attention on draining current from 12V battery at 500W is 42A, and consider battery manufacturer recommendations for discharging battery C/10. Also which battery to use starter or deep cycle lead acid battery, situation is not the same. Systems on 12V are good for up to max 500W, because high amperage, you need copper flat plates instead wires, and fire or melting can occur. For higher power use systems on higher voltages, such 48V, 72V,....


See example of inverter in attachment and creating a Sine Wave with a PIC16F84.

:wink:

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On this link you can download :

Ferrite transformer SG3525 Frequency Calculation Program
https://320volt.com/ferit-trafo-hesaplama-programi/


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On this link you can see:

SMPS Flyback Transformer Design Notes
https://320volt.com/fairchild-flyback-smps-trafo-tasarim-notlari/

 

[Tahmid]

thanx tpetar,,,
plzz tell me the mechanism of driving the mosfet gate through spwm,,,i mean ,by switching the mosfet in time domain ,how can we get sine wave output ,,,? suppose i have a square wave of 50 hz and i give this wave to mosfet gate then inside mosfet channel will be formed between drain and source at the rate of 50hz(alternatvily 20ms i.e 10ms channel will be formed and 10 millisecond channel will be empty) so by doing this we can get a squre wave output,,,i want to know than how this spwm do this ,,n also help me about spwm,,,,

For one half cycle (10ms), one high side MOSFET is kept high and the low side MOSFET on the other side of the bridge is switched at high frequency. During the next cycle, the MOSFET is kept off and the other side MOSFET is kept high and the other low side MOSFET is switched at high frequency.

A diagram should make this clearer:

During one 10ms half cycle, Q2 and Q4 are kept off. Q3 is first turned on and kept on for the entire 10ms. Q1 is pulsed at high frequency with variable duty cycle (changing sinusoidally).
During the next 10ms half cycle, Q1 and Q3 are kept off. Q2 is turned on and kept on for the entire 10ms. Q4 is pulsed at high frequency with variable duty cycle (changing sinusoidally).
This is called sinusoidal pulse width modulation (SPWM).