MAGNETIC PROPERTIES OF TYPES OF CORE FOR TOROIDAL TRANSFORMERS MADE FROM THIN LOW-LOSS SHEETS AND THERMAL INFLUENCE ON RESULTING TRANSFORMER IDLE CURRENT

Aleš Folvarčný – Martin Marek – Regina Holčáková

   The paper presents the results of independent experimental analysis aimed at determining the magnetic properties of the selected type of toroidal transformer cores made from thin silicone alloyed sheets with a low loss number used in our case in the manufacture of toroidal transformers for higher class audio power amplifiers. Another part of the paper deals with the results of the experimental analysis aimed at determining the effect of temperature on size and type parameters of the current loading of small toroidal and conventional transformers. The aim of this measure was to assess the effect of temperature and voltage values at no load current of the selected type of toroidal and conventional transformers put in a climatic chamber. Furthermore, our attention was drawn to the observations of the effect of temperature and magnetic saturation on voltage transformer cores and to approximate formulation of magnetic properties of metal core type transformers in the form of BH hysteresis characteristics. The samples were analysed and the waveforms U₁₀, I₁₀, U₂₀ were measured and recorded. The measured values were then used for calculation of additional quantities of toroidal transformers (magnetic flux density, magnetic field intensity) that specify the magnetic properties of the measured samples. Finally, the measured results of both the toroidal and conventional transformers were compared. The temporal analyses of saturation of cores are the outcome of extensive and time-consuming measurements and registration of signals in no-load state for various levels of supply voltage. The measurements were based on common knowledge of the properties of soft ferromagnetic materials.

Keywords: toroidal transformer, idly current, BH characteristics, climatic chamber, temperature

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