>>
Now if the primary power is from a "normal" constant-voltage source, then clearly the increase in XL and Z from removing the secondary load causes a corresponding decrease in the primary current.
<<PaulUK wrote>>,
Then heres a question for you . How does removing the load from the secondary increase the transformers reactance ? Or for that matter changing the primary voltage change the reactance.
According to Faradays Law, FLUX(m) = 1/Np(integral)Vp(t)dt((e{ind} = N * d(phi)/dt))
This equation states that the average flux in the winding is proportional to the integral of the voltage applied to the winding, and the constant of proportionality is the reciprocal of the number of turns in the primary winding 1/Np.
Ignoring for a moment the effects of leakage flux, from that equation we get
Flux = Vmax/(wNp) * Cos(wt) = Flux in Webers.
Hence if the primary voltage is reduced how does this change the Reactance of the transformer ?
Since as stated the 'a' turns ration is Ns/Np then the flux produced in the primary will be reduced by the amount of the applied voltage.
But I dont see how the reactance of the transfromer is changed by changing the voltage, as long as the frequency is constant.
WOC
