The principle of operation of a two-stage power transformer, T1 is the main one which has one more primary winding, with the same number of turns (N1). T2 is an auxiliary power transformer used to compensate for errors, assuming that the load is negligible.
In the case of a vacuum power transformer, the voltage drops cause the primary winding to fail, thus the electromotive force (Fem) will be lower than the primary voltage, and the magnetic flux φ will also be less than ideal. mrosupply
For primary low voltage power transformers (up to 1.5 kV), a two-stage construction can be concentrated, which has two magnetic cores and two primary windings.
A two-stage transformer has the same construction and principles as a two-stage current transformer. This relationship was recognized in 1964, supposing that with this constitution could have the same results as in active compensation. However, he did not analyze the errors and then several articles and books dealt with the subject.
The published procedures are based on the equivalent circuit, or are making some approximations and the results often do not originate the analysis of the errors directly.