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    Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    There is a lot article on this regards. And I try to follow there directions. But I stuck with LC filter. Can any one help me on this regards. I enclosed my H-Bridge circuit. I vision is to generate 50~100 Watt Inverter (220V, 50Hz) sine wave ac from a DC 12V battery with SPWM Technique.

    Click image for larger version. 

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    I used http://tahmidmc.blogspot.com/2012/10...rter-test.html guide line. I wish Thamid could help me out here. He is a very good researcher.

    Please response.
    Last edited by bkar; 5th December 2014 at 13:33.

    •   Alt5th December 2014, 13:24

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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    I am just a novice with this kind of inverters, but I think the LC filter is not correctly connected, you should use 2 inductors and 2 capacitors as two separate low pass filters.



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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Quote Originally Posted by BrunoARG View Post
    I am just a novice with this kind of inverters, but I think the LC filter is not correctly connected, you should use 2 inductors and 2 capacitors as two separate low pass filters.
    Could you please describe a little more please, as I am also novice about inverter



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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    This is a recent thread about a similar project. It has a discussion about how to filter the SPWM so as to end up with a smooth sine wave.

    http://www.edaboard.com/thread326601.html


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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Yes your L1, C7 filter is all wrong, see other designs



    •   Alt6th December 2014, 04:18

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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Quote Originally Posted by BradtheRad View Post
    This is a recent thread about a similar project. It has a discussion about how to filter the SPWM so as to end up with a smooth sine wave.

    http://www.edaboard.com/thread326601.html
    Dear BradtheRad,

    I just go through the thread. I forgot to mention other parameter. The parameter are below....
    1. My carrier frequency is 16KHz.
    2. I used 9-0-9 to 220 Volt, 50Hz, 5Amp rating transformer.
    3. I need to deliver 100W to the load(1~2M Ohm).

    As from link, you mentioned I changed the RLC filter as one of your recommendation. Please Check my output simulation result. Please help me to recalculate the the filter circuit or suggests me which type of filter would useful for me.

    Attachment 112106

    In the attached pic please check that two ac ammeter has connected one is before Filter circuit and other one is added just before Load circuit. There you'll see that a litter current as passed through first ammeter And there is no current pass through load. Can you told me why this is happen. If I connect a load that required 220VAC & 100Watt, what could happen?

    - - - Updated - - -

    Quote Originally Posted by Orson Cart View Post
    Yes your L1, C7 filter is all wrong, see other designs
    I modified my LC filter. Please check this one & help me to recalculate the LC filter parameter or any other suggestion.

    Click image for larger version. 

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    •   Alt6th December 2014, 06:23

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  7. #7
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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Quote Originally Posted by Orson Cart View Post
    Yes your L1, C7 filter is all wrong, see other designs
    Click image for larger version. 

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    Dear Orson,

    I uploaded the filter circuit. Is this setting right.

    Regards,

    Bahadur Kar



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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    No, you are not filtering the SPWM high frequencies, you need two inductors and two capacitors, you didn't put any of them but the transformer primary coil. You put a correct circuit but I don't see you have connected it to the push-pull output.

    Those are two LC low pass filter (look for the circuit, it's a L-C series with the output in parallel to the capacitor) working together as your amplifier is fully bridged. What you get with it is that the square wave coming from MOSFET push-pull is filtered so you get almost the same signal you put at the SPWM control input. If the filter is not well designed (take into account the inductor wire resistance) you will have oscillations and kind of sine waves at the output. You can simulate the filter and change the values till you get an acceptable minimum distortion.



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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    On the possibility this is what you're looking for...

    This simulation shows values that might work for your LC second order low-pass filter. Values are tailored to a 1500 ohm load.

    At least it gives some idea what the waveforms should look like.



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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Quote Originally Posted by BrunoARG View Post
    No, you are not filtering the SPWM high frequencies, you need two inductors and two capacitors, you didn't put any of them but the transformer primary coil. You put a correct circuit but I don't see you have connected it to the push-pull output.

    Those are two LC low pass filter (look for the circuit, it's a L-C series with the output in parallel to the capacitor) working together as your amplifier is fully bridged. What you get with it is that the square wave coming from MOSFET push-pull is filtered so you get almost the same signal you put at the SPWM control input. If the filter is not well designed (take into account the inductor wire resistance) you will have oscillations and kind of sine waves at the output. You can simulate the filter and change the values till you get an acceptable minimum distortion.
    Dear BronoARG,

    Can you please upload a sample filter circuit (picture) so that I can understand. I am very newbie on this topics. I am just asking (please help me in this regards) -
    1. Am I connect the transformer in correct order?
    2. If wrong Should I change it to Center Tap transformer? & How can I connect a center tap transformer with the H bridge out put ?
    3. Where should I applied filter circuit? At transformer's Secondary terminal where H bridge circuit's output are connected or the primary terminal where load is connected?

    Thank you
    Bahadur Kar

    - - - Updated - - -

    Quote Originally Posted by BradtheRad View Post
    On the possibility this is what you're looking for...

    This simulation shows values that might work for your LC second order low-pass filter. Values are tailored to a 1500 ohm load.

    At least it gives some idea what the waveforms should look like.

    Dear BradtheRad,

    I upload a picture what I understand from your picture. Please check figure. In your simulation you applied 6KHz carrier frequency, but 16KHz. Could you check it? Is transformer secondary:primary ration 1:38? what would be the core size? ( 9-9 to 220, 3Amp transformer or Any other recommendation ?) In your picture at the primary side there is a resistor 15K parallel with the transformer primary terminal, What would be its watt ratting. Suppose saying 15K, 3W. is it right ?
    I am just wondering, If I could make it in real hard ware. This is why I am seeking your help for purchase the right component for the inverter.

    Regards,
    Bahadur Kar

    Click image for larger version. 

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    •   Alt11th December 2014, 09:02

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  11. #11
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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    I realised what you wrote at the very end. Yes, the red surrounded circuit is right, I don't know if the values are correctly calculated but the connection is the appropiate.

    As I said before you must use two filters as it's a bridge amplifier, to supress the SPWM high frequencies.Click image for larger version. 

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    The values are not right but the filter connection to the transofmer and the load do.

    Hope it helped you



  12. #12
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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Quote Originally Posted by bkar View Post
    Dear BradtheRad,

    In your simulation you applied 6KHz carrier frequency, but 16KHz. Could you check it?
    I used a slower frequency which allows the scope traces to show the 50 Hz fundamental.


    Is transformer secondary:primary ration 1:38? what would be the core size? ( 9-9 to 220, 3Amp transformer or Any other recommendation ?)
    The transformer specs in the simulation appeared to work in the simulation. It is possible your own transformer will work better than the simulation.

    In your picture at the primary side there is a resistor 15K parallel with the transformer primary terminal, What would be its watt ratting. Suppose saying 15K, 3W. is it right ?
    The .05 and 15k resistors are unnecessary.

    The .05 ohm represents some amount of parasitic resistance. It may be in any number of components. By changing its value you can see how it affects the available power from your converter.

    I leave the 15k ohm attached so I can observe the raw waveform in the secondary. Or I change it to 1500 (the specified load) to make sure sufficient voltage, and sufficient amperage, is coming through the transformer.[/QUOTE]

    - - - Updated - - -

    My simulation is not perfect. No simulation can be. My design is not necessarily the optimal design.

    It is to illustrate concepts of operation. It shows how certain values affect operation. These are things which will assist you in your own design.


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  13. #13
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    Re: Help 50 to 100 Watt Inverter (220V, 50Hz) Design with SPWM Techniq

    Dear BradtheRad,

    Thanks for you cooperation. Now I am trying to do it in real hardware. I will keep you in touch. And again, thank you.

    Regards,
    Bahadur Kar

    - - - Updated - - -

    Dear BrunoARG,
    Now I am in the hardest part. Trying to build it in real hardware. Thanks for your advice. As you know I am not very goods in theory, but trying to understand it.Thanks for your support. I will keep you in touch.

    Regards,
    Bahadur Kar



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