In this paper the generation system of electric energy for the aircrafts is observed that bases on a principle of changing an equivalent magnet gap in the synchronous generator with constant magnets (PMSM) excited by changing consumed reactive current by a 3-phase voltage source inverter (VSI). Such system, which generates energy with two principal parameters - double range of frequency deviation from 360 Hz up to 720 Hz, and a stable value (115 V) of phase to ground voltage, is considered for aircraft implementation. Stable voltages are obtained by different mode of VSI operation. Also, the basic static energetic characteristics of such system are derived. This paper describes its relationships from frequency in defined range. Analytical results of current load calculation are presented in this paper. Mathematical modeling results are presented to confirm the basic principles of this approach. In addition, experimental unit is shown in this paper, but results of its working will be presented in following paper.