General principles and different couplings
Linear power networks

Consider an electrical system consisting of three independent loads Z₁, Z₂ and Z₃ supplied by three voltage sources e₁(t), e₂(t) and e ₃(t) (figure 1).

Every single-phase circuit has an "out" conductor and a "return" conductor, essential for completing the circuit.

Such a system has interesting properties in the particular case where :

• the three charges are identical (Z = Z ₁ = Z₂ = Z₃) ;

• all three sources are sinusoidal, of equal amplitude and 2π/3 out of phase.

The voltages e₁(t), e₂( t) and e₃(t)...