The great development of Large Variable Speed Wind Turbine Generators has caused a new interest in the Brushless Doubly-Fed Induction Machines (B.D.F.I.M) because they could be a feasible alternative to Wound Rotor Induction Machines (W.R.I.M). The B.D.F.I.M. has two different stator windings and a rotor cage that make it more robust than the W.R.I.M. The operation of the B.D.F.I.M. is possible due to the two stator magnetic fields couple each other through the rotor cage which has a special configuration. This paper studies these coupling mechanisms comparing simulation results, obtained with a Finite Element (FE) Model, and experimental result, obtained with a Prototype of B.D.F.I.M.