Dynamics of a small HAWT is studied. The closed mathematical model involving phenomenological description of both aerodynamic load upon turbine blades and permanent magnet electric generator is developed, in order to take into account the inductive reactance of the electric circuit. A series of experiments is performed in the subsonic wind tunnel of the LMSU Institute of Mechanics that allowed verifying the model and identifying its parameters. Parameters of dynamic model are identified, such as the coefficient of electromechanical interaction, the active internal resistance of generator, the circuit reactance. Parametric analysis of steady regimes is performed. The model prediction that HAWT operating dynamic system has two stable steady regimes (high speed regime and low speed one) is confirmed by experiments. Transient regimes are registered depending on parameters of the system, which allows estimating the unstable steady regime. The characteristics of the unstable regime are experimentally determined. Obtained results are used for estimation of aerodynamic moment acting on HAWT blades.