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core for inverter transformer

Discussion in 'Electronic Design' started by ruleworld, Sep 25, 2006.

  1. ruleworld

    ruleworld Guest

    I want to make a inverter transformer of 400w. in my local store i
    found many kind cores, all from old transformer mainly from ship
    breakings. some are heavy others not so heavy. some have black paints
    on it, some are gray, silver golden etc. I want to know which type is
    better for inverter transformer.

    and the transformers primary 12-0-12v should have bifilar winding.
    should i wind the secondary 220v loop over the primary? or should i
    wind them side by side.

    thanks
     
  2. ruleworld

    ruleworld Guest

    only cores are available.
     
  3. Assuming you can separate the laminations from the coils, I think you
    should be looking for a 500VA transformer with a 220 volt primary, and
    remove the secondary (usually on top) and replace it with your 12-0-12
    primary. You might even find a 220 to 24 volts center tapped to use
    as is.
     
  4. I'm guessing he is in India from the "ship breaking" reference.

    What frequency of inverter?


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  5. Phil Allison

    Phil Allison Guest

    ** Mad Groper Alert


    ** Oh dear - this Groper is really beyond all help.



    ...... Phil
     
  6. ruleworld

    ruleworld Guest

    he is a real time stupid.

    I ask the things i don't know. If u don't know the answer just stay
    out. u don't have to be a sucker.
     
  7. Phil Allison

    Phil Allison Guest


    ** But you did NOT ask them.


    FUCKWIT !
     
  8. ruleworld

    ruleworld Guest

    message reported
     
  9. Phil Allison

    Phil Allison Guest



    ** One cruise missile now on way to your location in Bangladesh .....


    LOL !!!



    ........ Phil
     
  10. ruleworld

    ruleworld Guest

    sure. not a thief like u or ur ancestors!!
     
  11. Play nice children. How is your Hindi - or other S. Asian language?


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    | | __ _ _ __ ___ | |__| | ___ _ __ ___ ___ _ __
    | | / _` | '_ ` _ \ | __ |/ _ \| '_ ` _ \ / _ \ '__|
    _| |_ | (_| | | | | | | | | | | (_) | | | | | | __/ |
    |_____| \__,_|_| |_| |_| |_| |_|\___/|_| |_| |_|\___|_|
    __ ____
    / _| | _ \
    ___ | |_ | |_) | ___ _ __ __ _
    / _ \| _| | _ < / _ \| '__/ _` |
    | (_) | | | |_) | (_) | | | (_| |_
    \___/|_| |____/ \___/|_| \__, (_)
    __/ |
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  12. There are several ways to design and build an inverter like the one you
    need. I assume you will have a battery input of 12 VDC nominal and want an
    output of 220 VAC at 50 or 60 Hz. If you will be using a "modified sine
    wave", which is actually a rectangular waveform roughly approximating a
    sine wave, you will have a primary waveform that is 12 volts peak, or about
    8 volts RMS, so you will need a primary of 16 VCT. You can use a pair of
    high current MOSFETs or bipolar transistors driven by a logic circuit with
    the proper on and off times for the frequency you desire. The MOSFETs will
    need to handle pulses up to 100 amperes and voltage peaks of 30 Volts or
    more. It will probably require snubbers and other components to keep the
    inductance under control under all conditions, especially if the load will
    be inductive or regenerative (motor).

    A standard EI lamination power transformer core will work OK, but I don't
    know if the cores you have available from freight salvage are suitable. The
    color of the paint is irrelevant. If they were soaked in salt water and
    have had the windings cut off, chances are the cores will be rusty and
    possibly damaged. You need to do core loss and saturation tests on them to
    verify that they do not have excessive circulating currents when they are
    energized. To do this, you must wrap a number of turns as a primary and a
    secondary, and apply voltages while you monitor the input current, actual
    power, and output voltage. From this you can determine the number of turns
    per volt at which the core just begins to saturate, and use this to
    determine the number of windings you need. The true power with no load
    determines the core loss, which should be no more than about 5% of the VA
    rating of the transformer.

    If the core is already assembled, it will be very difficult to wind it. If
    it is a C-core, you might be able to pull the halves apart and put new
    windings on a tubular form and put it back together, but usually the
    laminations are overlapped to reduce the magnetic gap. You could try sawing
    the cores apart, but that will cause shorts between the laminations,
    resulting in a very inefficient, noisy, and unreliable transformer. If you
    can find a toroidal core, as has been suggested elsewhere, you will need to
    wind it using a shuttle, but it will be more efficient.

    If you don't understand what I have been saying, then it is doubtful that
    you will be able to design and build an inverter successfully. You will
    need to do some research, learn the technology, do some simple experiments,
    and be prepared to spend many hours and lots of money for multiple
    prototypes until you finally have something that works.

    Or, you can spend about $30 for an automotive inverter and just plug it in.
    Your choice. Good luck,

    Paul
     
  13. Johnny Boy

    Johnny Boy Guest

    Hello ruleworld - how are you? We all have to be beginners sometime.
    Ignore Phil, he does know what he's talking about and is very knowledgable
    with electronics, but his people skills need honing. In short, he's a bit of
    a rude prick a lot of the time. (You might have done better to post in
    sci.electronics.basics rather than ....design)

    Among other things, the size and type of the core will depend largely on
    the frequency that you intend to run the inverter at, (as mentioned by
    Graham). (The higher the frequency, the smaller the core) If you're planning
    to use typical inverter frequencies ranging to 100kHz, an iron core intended
    for 50 or 60 Hz is not the best choice. What frequency did you intend?

    .... Johnny
     
  14. ruleworld

    ruleworld Guest

    Thanks Paul

    i will use a 12v battery and the output will be 220 VAC at 50Hz.

    i have done some homework and infact i made a inverter using only 555
    ic and some 2n3055 transistors. its output is square wave and not able
    to run inductive load. and the transformer i used is only 55VA. now i
    have decided to build a circuit using a pwm controller ic SG3524. which
    should run inductive load. and yes the circuit uses IRFZ44 MOSFETs.

    the cores are El type and i found some in very good condition. there
    are some cores which i will not need to saw bcoz they are tied by 4
    screws in the corner.

    the reason i asked for colour of the core bcoz i think they are not
    made of same iron.
    and i asked for weight bcoz for the same size their weight varies much.
    the heavier ones will cost me more bcoz they sell it per kilogram.

    could u plz answer the following questions.

    1. u said color does not matter. then what about weight?
    2. are the El cores which have 4 holes in corners and tied by screws
    good? they are very heavy also.
    3. and can i use SG3524N in place of SG3524? i am 99.9% sure i can but
    there is no harm in asking i think.
     
  15. Eeyore

    Eeyore Guest

    You do realise that a square wave inverter will only run certain kinds of loads ?

    Graham
     
  16. Phil Allison

    Phil Allison Guest

    ** Mad Groper WARNING !



    ** You will need a laminated iron core that weighs about 6 to 7 kilograms
    to handle 50 Hz at 400 watts.




    ........ Phil
     
  17. ruleworld

    ruleworld Guest

    comment from a thief cannot be taken seriously.
     
  18. ruleworld

    ruleworld Guest

    i was only talking about core. i have not said anything about waveform.
     
  19. Guest

    Phil isn't known to be a thief, and he is known for being well-informed
    about transformers. He's not my favourite person either, but you'd do
    well to follow his advice.
     
  20. Eeyore

    Eeyore Guest

    Is that a chip on your shoulder by any chance ?

    Graham
     
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