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2 wire transformer

Discussion in 'General Electronics Discussion' started by dick56, Aug 23, 2012.

  1. dick56

    dick56

    18
    2
    Apr 15, 2011
    I have a 2 wire transformer from a circular flouresant light. The transformer markings are, LEON -400, 118 volt, .32A, 22W. The transformer is burnt and there is no resistance between the two wires. I have never encountered a transformer with only two wires so I do not understand how this works. I do know that one wire is connected to one side of the 120 volt AC input and the other wire is connected to the on/off switch. The black 120 volt AC in line is connected to pins on the circular light. There is a green 120 volt input wire which is connected to the metal frame where the transformer sits although the transformer has an insulating cover surrounding the transformer.

    Any ideas how this works and what voltage is needed to make the flouresant light work? A search of the web does not show any transformer with these numbers. I would like to get a transformer to make this light work.
    Thank you.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    It's a ballast, an inductor designed to limit the current to the lamp.

    The numbers you have read off the ballast should be sufficient for you to find another one.
     
  3. john monks

    john monks

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    1
    Mar 9, 2012
    Steve is correct. The ballast typically connects to the hot line then to One terminal of a fluorescent light filament. The neutral line connects to one terminal of the filament on the opposite end of the fluorescent light. There is a pushbutton or starter connected between the remaining filament leads on opposite ends of the fluorescent light. Now what happens is when the starter or button is closed current passes from the line through the ballast and the filaments light up causing a conductive plasma to occur around the filaments. This helps liberate electrons from the filaments. So now then the button or starter is opened whatever current that was passing through the ballast wants to continue to keep going because ballast tend to resist the change of current. So for the current to keep going the voltage spikes causing the gas in the fluorescent light to ionize and therefore causing it to conduct and the light lights up.
    Typically a light runs around 30 volts. But it may take 1000 volts to start the light. Technically a fluorescent light is an arc light. This is why a ballast is used.
     
    Last edited: Aug 24, 2012
  4. dick56

    dick56

    18
    2
    Apr 15, 2011
    Steve and John, thanks for the replies. I Googled 2 wire transformer and the numbers, but no hits. Is it possible to put another step-up three wire transforner in the burnt out ones' place? Maybe a 4 to 1 step-up to see if that is enough to light the phorsphors?? What wires of the three wire transformer would be the ones to use?
    Thanks again.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
  6. davenn

    davenn Moderator

    13,349
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    Sep 5, 2009
    no, you must use a proper ballast inductor and while you are at it replace the fluro tube(s) and starter(s) :)
    understand its NOT a transformer there is no transformation of voltage

    They are a very standard item, follow steve's link for dozens of hits :)

    cheers
    Dave
     
  7. JMW

    JMW

    90
    3
    Jan 30, 2012
    This sounds like an 8 inch or so Circline lamp. If so, you can probably buy a new one for less than a ballast. If your lamp has some intrinsic value e.g. your mother in law gave it to you or it matches the other 40 or so in your home, buy a new one, remove the ballast, starter and lamp and install it your existing fixture.
     
  8. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    If you want to understand the function of a normal Fluorescent lamp, you can find good information in Wikipedia: Fluorescent lamp Starting

    It's right, as pointed out that the ballast is limiting the current in normal mode, but it also works as a "2-wire transformer" in a type of "flyback mode" together with the starter at start-up.

    You can simplified say it like this: When the starter is closed, the "2-wire transformer" stores the energy in its magnetic field (works as a primary winding).
    When the starter opens, the magnetic field is "pushing" the energy out of the "2-wire transformer" (works as a secondary winding), resulting in a very high voltage.
    This happens because the circuit is open and the energy must go somewhere, in this case it just raises the voltage higher and higher till a sparkle appears - hopefully inside the tube!
     
  9. szhighstar

    szhighstar

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    Aug 7, 2012
    please advise input volltage and current/ouput voltage voltage and current/ work frequency in your circuit, then recommend which transformer you should be select.
     
  10. davenn

    davenn Moderator

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    Sep 5, 2009
    read the first post and get the information you asked for
    Then read on and understand the type of INDUCTOR the OP requires

    Dave
     
  11. MHobson

    MHobson

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    Today
    I have a question about a 2 wire transformer. I have an LG refrigerator where the compressor does not function. It is a linear compressor and does not have the normal start relay. Power cables come directly from the main circuit board. Here in France the mains voltage is 220v, the compressor is clearly marked 220 - 240v but I am only getting 111.6v at the compressor. I have bought a brand new main circuit board but the problem persists. The only other components adjacent to the main circuit board which have not been replaced are a capacitor stamped 10mf, and it tests at 10mf, the other item is a two wire transformer. I have not come upon such an item before, normally I expect a transformer to have at least two pairs of wires, one for input voltage, the other for output voltage. Reading your article it seems that the transformer is a ballast, I have only seen mention of them in relation to flourescent lighting. I wonder if it replaces a start relay on conventional compressors. The unit plugs into the centre of the circuit board and if disconnected the refrigerator does not turn on when plugged in so the unit must achieve a certain level of function. When I researched transformer testing it seems that a resistance of between one and ten ohms is acceptable but over 10 ohms the unit should be changed. This unit shows a resistance of 0.4 ohms. I can see no advice as to what to do if the resistance is less than 1, and there is no printed value on the unit. I can buy a replacement part but it is not cheap and am hesitant about throwing even more money down the drain, it may be better just to dump the refrigerator, it just seems such a waste. Incidentally on this type of compressor there are only two of the three pins which have cables connected and across them I get 6.5 ohms. Can anyone advise me how I can test this part, it would be very valuable. I look forward to your comments, regards, Michael
     
  12. Harald Kapp

    Harald Kapp Moderator Moderator

    9,413
    1,924
    Nov 17, 2011
    Soyez les bienvenus,
    Michael.


    Had you read the previous posts then you'd understand that there is no such a thing as "a 2-wire transformer".
    The least amount of wires a transformer needs is 3 - that would be a so called autotransformer which does not offer insulation.
    A typical transformer has at least 2 separate windings which makes for 4 or more wires.

    Your "-wire transfomer" is likely an inductor. So pleas do not use the term "transformer" here.
    Inductors are used for all kind of purposes like:
    - filtering
    - energy storage (very short term)
    - high voltage generation (using the flyback voltage when current is turned off rapidly)
    - ballast (limiting current through the reactive impedance without incurring the losses as an ohmic resistor would)
    -...
    Not impossible but imho unlikely. Usually capacitors are used for starting AC motors.

    I doubt this rather general assertion holds true. Depending on the intended use of an inductor resistances even in the kΩ range may be acceptable.

    Depending on the accuracy of your Ohmmeter this is a perfectly acceptable value for a power inductor.

    Right so. What makes you think it is this inductor that fails and not the compressor itself?

    Please post make and model of your refrigerator, along with some clear pictures (note: ~ 100kB size limit per image) so our members may have a look at the issue and can come up with suggestions.

    By the way: next time better open a new thread of your own instead of hijacking a 7 year old thread. That helps to keep confusion at a minimum.


    Salut,

    Harald
     
  13. MHobson

    MHobson

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    Please see attached files: 20191212_114637-640x480.jpg 20191212_114859-640x480.jpg 20191212_115246-480x640.jpg 20191212_115346-640x480.jpg
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The circuit diagram is too small to read. In addition it shows two variants: basic and deluxe. Which one do you have? Please post a larger image of the relevant section. It will help if you mark the inductor in question.
    Your other pictures are clear but not very informative. What is not clear is where the inductor goes.
    Have you checked the start relay? For testing purposes only you can temporarily bypass the start relay.
     
  15. MHobson

    MHobson

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    Today
    I will have a look at the circuit diagram again, I am not sure exactly which section is appropriate, I think this is the deluxe variant with water/ice dispenser the other variant does not have this option. As I said in my post, the LG inverter compressor does not have a start relay, which is why I suspected the inductor may have been for that function, I have an older LG refrigerator with start relay, but it does not have an inductor connected.
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    I'm sorry, an oversight on my side.
     
  17. davenn

    davenn Moderator

    13,349
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    Sep 5, 2009

    your second phot shows an inductor aka a choke
     
  18. MHobson

    MHobson

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    Today
    OK thank you, bear with my ignorance, but if it is a choke and the circuit board is dead when it is disconnected, does that mean it is limiting voltages specifically on the circuit board rather than limiting voltages sent to the compressor, in which case the only remaining culprit is the electrolytic capacitor. I was unable to test myself as I only have a digital meter, a friend tested it for me. I will not know if the compressor is faulty unless I can supply sufficient voltage.
     

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