transformer tuned

Discussion in 'Wireless & RF Design' started by Thevenin's Planet, Aug 26, 2009.

  1. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    Hi!

    I AM CONSIDERING TO USE A TRANSFORMER AS PART OF A TUNED CIRCUIT.
    iTS A 120 PRIMARY AND 6 VOLT SECONDARY, CLASS 2,360 mA. The predicatment is what induction is being used,mutual induction,leakage induction or both? And can found out the induction without using a LCR meter?
     
  2. ryta

    New Member

    Aug 27, 2009
    4
    0
    I'm looking for a "variable resonant transformer" or basically a transformer which I can change the resonance of.Alternatively, can you provide a link with how to make a resonant transformer tuned to a frequency of my choice?
     
    Last edited by a moderator: Aug 27, 2009
  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287
    What sort of frequency are you looking for.
    Sounds like a filament transformer, which probably has about 1Hy of primary inductance.

    eric
     
  4. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    60 hertz is the input. Your assumption is that the primary is One Henry. In order to tune
    the secondary with a capacitor both primary and secondary must be known,in which the
    Mutual Inductance can be determined. And from the Mutual,primary inductance and secondary inductance the k,that is, the coefficient of the coupling can be determined.So
    the L1,L2 must be measured. This data is not supplied in the Allaboutcircuits study books.There is a processor that is called open circuit test for determining the core loss and exciting current. A voltmeter,ammeter, and wattmeter is used. Do anyone can explain this farther?
     
  5. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    Lets try this again.If I want to make the secondary coil of a transformer as a tank circuit
    should I use the secondary coil inductance or mutual inductance? The secondary coil will be in parallel to a capacitor.
     
  6. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    Make the oscillator with some known value capacitor, measure the frequency and calculate the inductance that gives that frequency with that capacitor?

    If you can't actually build the osc around the transformer, just use the transformer + cap as a tuned circuit and sweep it with a signal generator while monitoring with a 'scope and look for the resonance peak.

    It's such an unusual application I doubt you will get any really useful info by any other means.
     
  7. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    The oscillator is the 60 hz outlet,120 volts. The secondary of the transformer is what I attempting to use as forming the tank circuit that will resonant with a capacitor that will agree with the secondary inductance. I don't have the tools to measure frequencies.I assuming that placing a capacitor in the secondary of the transformer would be in parallel to the secondary inductance. The transformer ratio is 120 primary and secondary 6 volts. XL =XC should resonant. Finding the inductance of this secondary seems to be difficult, since I'am learning with only multi- volt meter. The transformer is ac to ac. 120 ac pri to 6 ac sec.3 watts,360 Milliamps. Assuming that currents and voltages in a parallel or series circuit has some kind of mathematical relationship. which I am not sure of at this moment,hoping someone may know. In order that the secondary induction can found.
     
  8. davebee

    Well-Known Member

    Oct 22, 2008
    539
    46
    I'm wondering if doing this might lead to an overcurrent problem.

    A parallel resonant tank circuit shows high external impedance, but has a large internal circulating current.

    At power line voltages and fairly low resistance transformer windings, if a powerline transformer is brought into resonance, could the tank current build up to a strength that could overheat the transformer or capacitor?
     
  9. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    I don't know about how much current it would consume, but that's a idea for me to ponder upon. I was wondering would the capacitor would be in series to the secondary? I read something concerning that regarding tunning circuit front end of the radio.Also pick up some information about the load being reflected into the primary from the secondary.This project seams to be a bit complex then anticpated.
     
  10. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    My pondering brought forth the idea of what is Induction ?So far it seem to me to be the magnetic flux in alternation.The stop and turning back toward the opposite direction or changing polarity.Its said that this magnetic flux or force lags behid the magnetizing force.Futhermore the their other losses that may add to this Induction.I have the intention to use Mutual Inductive Reactance.But when the voltage is induced in the secondary when a current is being drawn fron the secondary their is this reverse induction which ,if I am right, Mutual Induction or Mutual Inductive Reaction.I am wondering if its possisible to separate these two,that is, the Primary and secondary XL? Futhermore I have discovered that I need a bridge circuit to make any type of measurements.And that's another problem, the componets values that is needed ? Is it two varible or one ? Its mentioned the ratio and an another variable.
     
  11. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    Attention !
    I'am still working with the transformers.Next thought, I have not done this yet, but if I short circuit the primary or the secondary will this isolate that specific coil to register inductance reactance by current and voltage.I am aware that the short circuit will produce a voltage of zero or vrey close to it depending on the Z in that specify coil .Will this effect the reactance of that specify coil? Will this effect the mutual inductance or will it elliminate it from that specify coil that I am measuring for XL.
     
  12. Mathematics!

    Senior Member

    Jul 21, 2008
    1,022
    4
    Sorry, If I am intrupting. But I am curious about a few questions rasied in this thread.

    First your using a transformer to convert the 120 volt 60hz AC into a lower voltage and higher current. The transformer on both the primary and secondary side will both be cycling at the same 60Hz. So your carrier frequency will be at 60 hz.

    Can you buy transformers that go from 120 volt 60hz ac to something like 12volt 500hz ac? (something different then the 60 hz on the secondary but have the primary at 60hz ) i.e transformers that transform frequency as well as voltage/current ?????????

    Correct me if I am wrong with the below stuff
    Ok so when you add the capacitor in parrell to the secondary coil of the transformer then you can create a carrier frequency determined by
    1/2*pi*sqrt(LC) where L = the inductance of the secondary coil , and C equals the parrell capacitors capacitance.
    If this is true then by sticking enough capacitors in series/parrell you can create almost any carrier frequency you want.

    The only thing I am worried about with this idea is the high current in the secondary coils. Will this damage the capacitors being used or do they sell capacitors to with stand this current being drawn ???? If Yes then cool you have found away to broadcast with alot of power. (NO NEED FOR A POWER AMPLIFIER AND you would probably get some serious range in broadcasting.) However FCC would be after your butt.

    Either way if you get the tank circuit working how are you thinking about modulating your data. Just with a mic and antenna in series between the capacitor and secondary transformer coil!

    If that is possible do they even sell mic's that can with stand that much current?
     
  13. Thevenin's Planet

    Thread Starter Active Member

    Nov 14, 2008
    183
    1
    Hello !
    Actually a transfromer can't produce frequencies,only reproduce it or transfer it to another circuit.Secondly,the coils of the transformer can be use to form a filter of some sort.To actual produce different frequncies a continous wave of some sort must be manipulated by capacitor(s) and,or coil(s).If I try to use 60 Hz as a carrier wave the wavelength will about18.83 feet. That seems to relate to a very large arial wire.
    The purpose of these threads is to attemp to find the Inductances of the primary and secondary coils using only Radio Shack analog Multimeter,which is very limited as far as the DC current goes to only 250 Ma.Also the meter only can register DC current.
    So I gather some data that says to place a resistor in the particular coil that is being tested for the inductance which is also connected to the a.c. supply.The opposite coil is to be short circuit.This was done. The results is a Pot was adjusted to divide the voltage between coil and the series resistor. Which is 1000 ohms and about 6 a.c.v. across each. I noticed that with open circuit the voltage was on the other coil was lower but this was frist try at 2.2 kiloohms. R1 was 4vac and 10 vac on the coil.The output of coil was 5 acv. Besides I use 13 vac as input through a 120v/6 vac transromer. The question, is this the isolated inductance reactance of tha picticular coil or mutual and measured coil ?
     
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