transformer and freq. ???????

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ahmed osama

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How the freq. change the transformer ??

does the ratio N1/N2 change with the freq.??

and

does N1/N2 equal to L1/L2??
 

Inductance is proportional to the square of the number of turns.

The low frequency limit of transformers is related to the winding inductance compared to the external circuit impedance.

The high frequency limit of transformers is related to the parasitic capacitances between winding turns.

This latter is why physically smaller transformers can operate over a higher frequency range.
 

I think you're forgetting the mutual inducance M. M = k*√(L1*L2) where k is the coefficient of coupling. If all of the flux from coil L1 passes through L2 then k is 1. If none of the flux from coil L1 passes through L2 then k is 0.

In general

V1 = L1*dI1/dt + M*dI2/dt

and

V2 = L2*dI2/dt + M*dI1/dt

If the secondary was open, the voltage on the secondary would be

V2 = M*dI1/dt = M*V1/L1 = V1* k√(L2/L1) so V2/V1 = k√(L2/L1)
 

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