ANALIZA UNUI ECRAN MAGNETIC POZIțIONAT ÎN SPAȚIUL DINTRE ÎNFĂȘURĂRILE UNUI TRANSFORMATOR MONOFAZAT, DE MICĂ PUTERE

"This paper aims to analyze the impact of using a thin magnetic shield placed in the space between the primary and secondary winding of a simplified, low power, single-phase transformer used in energy harvesting applications that demand power transformers not only in the energy conditioning stage but also in the energy harvesting stage. By using magnetic shields, the saturation of the ferromagnetic core and, in some particular cases, the destruction of electronic devices is avoided. For this purpose two scenarios are studied: one which doesn't take into account the magnetic shield, as it considers only the air space between the primary and secondary windings, respectively, and the second case study which considers a magnetic screen placed in the centre of the air space domain. The size of the air space domain, d, is varied as the secondary winding distance itself from the primary one until it reaches the core. The number of turns in the primary and secondary winding is equal, N1 = N2 = 300 turns. By moving the secondary winding away from the primary winding, the variation of the distance d between the coils is achieved, thus keeping the same cross-section of the secondary winding. The thickness of the magnetic shield is chosen arbitrarily, as thin as possible, with a dimension of 400 µm. The idealy, 1:1, simplified, low-power, single-phase transformer powered by a harmonic voltage supply at V1 = 20 V and at a frequency, f = 50 Hz, with load resistance of Rs = 100 Ω, is analyzed in a time-dependent study and its computational domain is taken from literature [4]. Different materials can be used for realizing this magnetic shieling, even copper and aluminum, but in this paper a magnetic sheet metal material is considered because of its small, almost nonexistent electrical conductivity. Our goal is to analyze the effect of magnetic shielding on the saturation of the ferromagnetic core, and the reactance and resistance values of the primary and secondary winding, respectively, for different dimensions of the air space, d. For comparison purposes, the second model, the one in which we have the magnetic sheet metal, an analysis is performed in the permanent harmonic regime, in addition to the one performed in the dynamic one."