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Help needed in push-pull circuit for Inveter.

Discussion in 'General Electronics Chat' started by koolguy, Oct 2, 2012.

  1. koolguy

    koolguy Active Member

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    Do you think it will work for all AC LOAD??
    I have also seen that when i have connected a CFL of 18W on my 12W INVERTER it was blinking very low but a low power filament bulb was glowing(dim) as shown in last pics...
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    If the output voltage of your inverter is too low then the lights will be dim.
    You are using a cheap tiny 12W transformer. Its voltage might drop when loaded with only 10W or less.
    I have never seen a incandescent mains bulb less than 25W.
     
  3. koolguy

    koolguy Active Member

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    Please tell me more about these transformer(voltage rating which one to buy), i will buy this..
     
  4. dave

    Dave New Member

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  5. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Look at www.digikey.com or www.newark.com for powerful dual windings transformers. You can look at manufacturers like Triad or Hammond. I don't know if you can get them in your country.
     
  6. ChrisP58

    ChrisP58 Well-Known Member

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    I realize that the circuit shown in post #40 was to show how to drive a transformer that doesn't have a center tap, but there is a big problem with the way that the mosfets are driven.

    The gates of the P and N channel mosfets are tied together. This means that there will be a brief time during switching transitions when both mosfets are turned on, causing a direct short between +12V and ground. This condition, known as shoot through, is a big killer of mosfets. Even when they don't die quickly, there will be a lot of power wasted.

    http://www.electro-tech-online.com/attachments/
     
    Last edited: Oct 16, 2012
  7. koolguy

    koolguy Active Member

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    I want to know that can we use fuzzy logic or neural network for any mean in UPS like for controlling purpose??
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Sorry, I cannot understand your broken English.
     
  9. koolguy

    koolguy Active Member

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    never mind, i am asking that how can we use fuzzy controller in UPS.....
     
  10. audioguru

    audioguru Well-Known Member Most Helpful Member

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    You want the output of the inverter in a UPS to be properly controlled.
     
  11. kubeek

    kubeek Well-Known Member

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    Ritesh, I just can´t understsand your logic. You can´t even make an inverter work properly without any control loop, and still you ask how to apply things like fuzzy logic and even neural networks, which most people here either have no clue about or they never heard of it.

    You need to learn to do things in small steps.
     
    Last edited: Oct 17, 2012
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  12. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    yes you can
     
  13. koolguy

    koolguy Active Member

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    OK, i have connected that 4001 IC but the voltage level is down ~136Vnow what to do??
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    You cannot measure the stepped modified sine-wave with an ordinary meter that is calibrated for a real sine-wave.
    My meter measures "True RMS" so it might read the voltage accurately.
    The transformer must be 9V-0-9V for the average output voltage to be 240VAC and the peak-to-peak voltage to be 340VAC.

    Maybe your little transformer is too small and is too cheap.
     
  15. koolguy

    koolguy Active Member

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    But the 12 0 12V should work fine to convert 12V DC to AC??

    The small transformer is used or testing after that large rating will be used.!!
     
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    No.
    If the transformer is perfect (most have a voltage drop when loaded) then the peak-to-peak output voltage (shown on an oscilloscope, not on a meter) will be 240V. But the new circuit has a modified sine-wave waveform so its average voltage will be only 170V.
     
  17. koolguy

    koolguy Active Member

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    That mean now i have to change 12 0 12V to 9V transformer??
    and I have seen the transformer used in low power UPS (600VA) in that transformer there are many tapping should i buy that??
     
  18. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The modified sine-wave inverter needs a 9V-0-9V transformer. a square-wavew inverter can use a 11V-0-11V or 12V-0-12V transformer.

    I don't know if the output of your UPS is a pure sine-wave, a modified sine-wave or a square-wave so I don't know the voltage of the taps on the transformer. Some of the taps might be used to charge the battery.
     
  19. koolguy

    koolguy Active Member

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    OK, if it Square wave so what will be tap winding...
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    On a square-wave, the average voltage is the same as the peak-to-peak voltage. The Mosfets have a small voltage loss.
    but a charged 12V lead-acid battery is about 13.2V so the output of the 12V-0-12V transformer should be 240V average or peak-to-peak when loaded. The voltage will be higher when the load current is small.
     
    Last edited: Oct 20, 2012
  21. koolguy

    koolguy Active Member

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    After using 9 0 9V transformer my multimeter is showing the same reading , why??
     

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