Design of a transverse flux machine for power generation from seawaves

Abstract

Linear electrical generator has been recently studied for the exploitation of sea wave energy, however the definition of the optimum geometry to be used is still debated and due to the fact that seawave energy is characterized by low speed and very high forces, a generator which is able to convert energy at low speed and high force is needed. In this paper we investigate the possibility to use a transverse flux linear generator (TFG) because transverse flux technology presents the highest force density per volume index among the iron based electrical machines. The advantages of TFG topology against the classical longitudinal concept are [1]: (a) the magnetomotive force per pole is independent from the total pole numbers; (b) the magnetic flux geometry and the coil section are independent design parameters; (c) armature coils geometry is simple; (d) phases are magnetically decoupled. Exploiting this advantages we have designed a TFG for power generation from seawaves. Since the TFM’s flux path is intrinsically 3D, a 3D finite element analyses has been used to design the motor. In order to optimize the design, several simulations were done assuming well defined constraints. In each simulation the electrical and geometrical parameters of the generator were varied and rotor was supposed to be acted by a water wave train. The wave train consisted of ten oscillations. Each oscillation of the train wave had an amplitude and a frequency generated through a random number generator whose statistic features were obtained from the experimental data of actual seawaves. The objective function was the maximization of energy output and the constrains were the volume of iron to be used. This approach leads to determine a well defined geometry of TFG. This geometry has been used to numerically simulate the generated electromotive force, the power output, and to evaluate the maximum mechanical stress on the generators parts