To analyze a more complicated construction sometimes it is necessary to take into account the physical construction of the current transformer. The next step confirms that these expressions based on the equivalent circuit can achieve the same results based on physical construction. The vacuum current I0 is shown by the current transformer construction parameters and to maintain the flow we need the no-load current, I0.
To maintain current I2 in the secondary circuit, we need a Fem E, induced voltage, on the secondary winding, which is balancing the voltage drops: The formula is E = I2 (Z2 + Zc) (21) where Z2 is the internal impedance and Zc is the external impedance.
To maintain the flux, we need an excitation, which will be the difference of the primary excitation, θ1, and secondary, θ2. In some situations, it is more practical to make the calculations by the equivalent circuit of the current transformer.
Because of the power mode the impedance of the primary winding is not interfering with the distribution of the currents, and therefore is not simulated. Thus, Z2 is the internal impedance, defined by the secondary winding.