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Re: [TCML] Calculate Output Voltage



Mddeming@xxxxxxx wrote:
You're right. It's Wrong. That formula is correct for non-resonant, iron-core transformers with coupling coefficient close to 1.00. A better theoretical value is Vs=Vp x sqrt(Ls/Lp), where L is the inductance, and this is an upper limit. Hitting 80% of this value requires a very well designed and tuned coil.
Not completely wrong, as inductance is always proportional to the square of the number of turns. If it were possible to wrap a primary coil along all the length of the secondary coil, the voltage gain would be close to the turns ratio, as both coils would have almost the same geometry. But as the coils don't have the same geometry, the voltage gain is the turns ratio multiplied by a constant, smaller than 1, that depends on the exact geometry. The voltage gain can also be written as sqrt(Cs/Cp), where Cs is the total secondary capacitance and Cp the primary capacitance. As LsCs=LpCp for a correctly tuned coil, the result is the same.

Antonio Carlos M. de Queiroz
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