Two-Phase System for Generating a Higher-Frequency Rotating Magnetic Field Excited Causing Hyperthermic Effect in Magnetic Fluids

This article presents a new method of excitation for a fast-changing rotating magnetic field ( RMF ) of higher frequencies (HF) causing the hyperthermic effect in magnetic fluids. The method proposed here uses a magnetic field exciter (inductor) consisting of a ferrite magnetic circuit and a system of coils connected in a two-phase arrangement. The proposed system is powered by two higher-frequency rectangular signals, with a 90-degree phase shift between each other, through HF transformers with ferrite cores. This paper presents the outcomes of the operation of RMF s in the frequency range of 38 kHz to 190 kHz, with a value of amplitude of magnetic field intensity H equal to 20 kA/m and increasing temperature, in a sample of APG513 magnetic liquid. The obtained results show that, in the range of the magnetic field intensities of moderate values, at a constant frequency f , the values of the time derivative of temperature are proportional to the square of the magnetic field intensity dT / dt ~ H 2 . Moreover, the values of the temperature rate, which are measured with the constant value of the magnetic field intensity, are proportional to the square of the frequency dT / dt ~ f 2 . At higher amplitudes of the RMF , the relationship dT / dt ~ H 2 is no longer fulfilled, and an inflexion point of this function appears. In the case of the highest values of the achieved intensity amplitudes ( H = 20 kA/m), the parameter of the Langevin function achieves a value equal to ξ = 6.