Transformer - homebrew

Discussion in 'The Projects Forum' started by montanamac, Nov 30, 2008.

  1. montanamac

    Thread Starter New Member

    Nov 30, 2008
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    Q. If I have an AC power source of 100 volts at an odd hertz of something like 250 Hz is there any reason why I cannot build a transformer with this input on the primary and 14 VAC on the secondary? I would be using a salvaged core from an old transformer to wind new transformer wire after stripping the old winding from the used core.

    This 14 VAC would then be rectified to DC to be used to charge a battery bank.

    The only transformer information I have seen has to do with either 50, 60 or 400 Hz. Is there some reason why only these frequencies are mentioned other than they are the standard ones used by countries or military? Is there some sort of electrical "rule" that would prevent the project above?

    Mac
     
  2. onlyvinod56

    Active Member

    Oct 14, 2008
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    There z no restriction for the frequency. And i know that a normal transformer can operate for different frequencies.
    But for a very low/high freq.,, core losses vary and hence efficiency reduces.
    worldwide the supply operating frequencies are 50 & 60Hz. Thats y most of the trnsfrmrs are designed so.
    In smps (switched mode power supply) the transfrmers are subjected to very high frequency pulses.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    If it's an old 400 Hz transformer, then the core won't be efficient at 60 Hz. Which is not to say it won't work, but you might not get the expected result, and power handling might be puny.
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
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    Some interesting information from another specialized forum:

    I wonder why! If the core can take hysteresis losses at 400Hz, wouldn't it be able to handle 60Hz. The copper losses should be less because of more skin depth, if that is even applicable. Maybe it has to do with the eddy currents and too thin of laminations.

    Anyone know the reasoning? I'm curious!

    Steve
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I think it's because the primary (magnetizing) inductance on a 400Hz transformer will likely be less than that of a 60Hz transformer. Put 60Hz into the 400Hz transformer and the current will be excessive, causing excessive dissipation (heat) in the primary winding resistance.
    I have a Triad isolation transformer that runs at 140°F with no load. I think it's because they used less copper to save on cost. My point is that the magnetizing inductance is low, which makes it run hot.
     
  6. leftyretro

    Active Member

    Nov 25, 2008
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    FYI for you younger types ;) , most of the 400hz transformers were used (still are?) in aircraft applications in WWII. For the same power wattage output a 400hz transformer is significantly lighter then a 60hz transformer, and in aircraft use weight is everything.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    As far as I know most military aircraft still do. My dad retired from the airforce in the 70's, where it was still the standard. Don't know about commercial, but I suspect it is there too.
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    That's because they don't need as much wire to achieve the required inductance.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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    The Navy was using 3 phase 400 Hz in electronic equipment at least until 1974.
     
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