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Design of Inductors and High Frequency Transformers presents of calculation of inductors; calculation of the wire; calculation of High Frequency Transformers; calculation of the winding conductors. | Page 29 Design of Inductors and High Frequency Transformers Inductors store energy transformers transfer energy. This is the prime difference. The magnetic cores are significantly different for inductors and high frequency transformers Inductors need an air gap for storing energy transformers do not. Transformers for flyback converters have to store energy which means they are not a high frequency transformer but they are in fact an inductor with primary and secondary windings. The material of the cores is normally ferrite. In addition to this other marterials with high permeability and with a high saturation point are used. Calculation of Inductors An inductor with certain inductance L and certain peak current I can be determined by the following calculation Inductors should store energy. The stored energy of an inductor is W 21LI2. This energy is stored as magnetic field energy within the ferrite core and within the air gap see Fig.5.1.1 . The higher the required stored the energy the larger the required core. The size of a inductor is approximately proportional to the stored energy. I inductor current N number of turns A cross-section area of the core lfe magnetic length of the core S air gap O magnetic flux B magnetic flux density Hfe magnetic field strength within the ferrit Hg magnetic field strength within the air gap Fig. 5.1.1 inductor with its magnetic and mechanical sizes The field energy in the inductor is W 1 iH-BdV pFe BFe VFe 1Hs-Bg -Vs 1 22 2 energy in the ferrite energy in the air gap The magnetic field density B is continuous and within the air gap and the ferrite is approximately equal i.e. B BFe BS . The magnetic field strength H is not continuous within the air gap it is increased by a factor pr compared to that than within the ferrite. If this is substituted into equation 1 and considering B p 0 p r - H VFe lFe - A and V5 S- A this leads to Page 30 W 1B 8p pr of the ferrite amounts to 1000.4000. It should be noted that the magnetic length of .
