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Thread: Calculation programs for transformers and inductors

  1. #121
    Hi,

    I have a problem, the results are not showing well. see attach:

    Sin título.jpg

    What could be the problem??


    Thanks
    Andres

  2. #122
    .... Silvio's Avatar
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    Quote Originally Posted by aadf View Post
    Hi,

    I have a problem, the results are not showing well. see attach:

    Sin título.jpg

    What could be the problem??


    Thanks
    Andres
    Hi Andres I do not know what is exactly your problem but it could be that the Excellent IT program got corrupted in some way. If your problem persists download it again and delete your previous version. However I calculated it for you with mine.

    In the first calculation I used a switching frequency of 50Khz and an output voltage at 50v. The answer to this output voltage is not real if your smps is for audio purpose. remember that the smps is not regulated and the voltage will rise to the peak value. This voltage will rise to around 60v on the high input voltage, however you can check the peak by moving the mouse pointer at the output voltage where you will have 3 for a non regulated SMPS. I marked these with 3 red arrows. The output inductor if you are going to fit one is not really needed as the pulse width with the IR2153 runs at 50% duty. You can put a smaller one say around 5uH or so but this will create voltage drop. The higher the inductance the higher the voltage drop at load. The inductor will also limit a little the inrush current at start up charging the secondary capacitors. One other thing at a current density of 5A/mm² in the first calculation the winding fill factor of 0.3 is exceeded and the windings may not fit in the transformer bobbin, you can use 6A/mm² instead.

    I suggest using a higher frequency say 60-68Khz. This will still use a copper wire dia of 0.5mm. Having a higher frequency the trafo will need less turns and gives a little more power. I made a calculation for you in the second screen shot at 60Khz and a lower voltage of around 40v, when you move the mouse pointer on the output voltages you will notice that the peak voltage is around 52 at the rated input voltage. Usually this voltage will be maintained during amplifier operation as music does not draw continuous power.

    trfo calc.JPGtrafo calc 2.JPG

  3. #123
    Hi Silvio,

    In my work computer, the IT(7300) have that problem. In another computer doesn't even start. It must be some incompatibility of regional configuration or something like that. Now i'm using the 4000 version, but it shows one less wire in the primary:

    IT4000.jpg

    Its my first smps with IR2153, based on NS450. And yes, is for audio. The inductor at the output is only 2.5uHy, but like you said, is not really needed.

    I made a transformer with 36turns in the primary and 12+12 in the secondary (1/2 primary + Secondary + 1/2 primary). The output is 51vcc.

    My final idea is to use a ER 44/22/15 for more power. What I don't know is how to calculate or obtain the correct frequency, since these cores are recycled and I don't know what material they are made of.

    Thanks so much for your support!
    Andres.

  4. #124
    .... Silvio's Avatar
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    Hi Andres, I also use recycled cores when I find them. I usually take the trouble and try to figure out the operating frequency they were working with by observing the type of chip and its timing resistor and capacitor. Observing the number of turns in the primary and trying to make out what flux density was used comparing with Excellent IT. At least I would have an idea more or less what type of material the core has.

    As you may have already noticed that different core material take different number of turns per volt. In any case while you are experimenting you can try out what suits best . Keep in mind that ferrite cores tend to get a little hot in operation and do not be afraid of this. The temperature rise is normally calculated at 25 degrees above ambient so reaching 50 and 60 degrees is no big deal. This feels hot to touch but do not be mislead the temperature of the core must not exceed the 100 degree mark. Here is why I always say that adequate tapes must be used (Mylar tape) as other types tend to get hot and soften up or melt at times.

    If the core material is unknown then use N27 as core material this will give you more turns for a given voltage. If the turns are more than necessary then the core will loose power, getting it right will get you the best result.

    A good calculation you can adopt for half bridge, full bridge and push pull typology is :-

    Nr. turns primary =155* 10^8 / 4 X freq in Hz X flux density in Guass (1200-2000) X core area in cm^2

    The flux density will vary according to the frequency used. To give you a rough idea at 20Khz you can use 2000 guass for 50-60 Khz you can use 1500-1600 Guass and for 100Khz you can use 1100-1200 guass. You will see that the higher the frequency the lower the flux density used. This is because the higher the operating frequency the hotter the core will get due to losses.

    Lastly with an ER44 transformer you will get around 500w and 700w peak at a medium frequency of 60 to 70Khz.

    I suggest you read some blog posts that I posted on this website so that you learn more about transformer winding practices. you can also take a look at the video on youtube of me winding a small transformer for smps.

    Link https://www.youtube.com/watch?v=_K3ixhcTYFg&t=1s

    Regards, Silvio

  5. #125
    diysmps Senior Member res_smps's Avatar
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    Quote Originally Posted by aadf View Post
    Hi,

    I have a problem, the results are not showing well. see attach:

    Sin título.jpg

    What could be the problem??


    Thanks
    Andres
    I also got a problem in Windows 10 64bit . I used Windows 7 64bit before and it worked fine

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