This paper presents an analysis of the power transfer between two DC circuit by use a single phase galvanically isolated dual active bridge -DAB. The analytical description of instantaneous values of the currents in both DC and in AC circuits of the DAB is done. The influence of the dead time as well as voltage drops across the transistors and diodes of the bridges is examined. The different relations between voltages of the DC circuits coupled through DAB and various phase shift ratios are considered. The analytical relations describing the average values of the currents in DC circuits are derived. These currents can be used to predict the power in both DC circuits and power losses generated in semiconductor devices of the converter. It is assumed that the voltage drops across these devices in conduction states are constant. The calculation of the transferred power as well as power losses and energy efficiency for the DAB converter power rated 5600 VA which is used to energy transfer between DC circuits 280 V and 51 V±20% is presented. The proposed relations and calculation results can be useful for preliminary evaluation of power losses generated in semiconductor devices and for design of the cooling system. Due to the high switching frequency of 100 kHz, the phase shift modulation for the control of DAB is used. To validate the theoretical investigations a few experimental results are presented.
This paper presents the implementation of a thermal camera for the quantitative estimation of power losses in a high frequency planar transformer (100 kHz/ 5600 VA). The methodology is based on the observation of the transient temperature rise and determination of the power losses by means of curves representing the derivative of temperature as a function of power losses dissipated in the transformer. First, the thermal calibration characteristics had to be obtained from a simple experiment, where power losses are generated by DC current in the ferrite core and windings. Next, experimental investigations focused on the determination of the transformer power losses for a short circuit and no load, with a resistive load and with the rectifier as a load were carried out. Finally, to verify the obtained results, analytical calculations based on Dowell's and modified Steinmetz's equations were additionally made, which showed a good convergence. The proposed method is easy to implement and can be used as an alternative to the calorimetric method which is time-consuming and requires a complicated measurement setup.
This paper proposes a model of a coupled inductor which takes into account the influence of frequency, temperature, and a constant component, IDC, of currents in the windings on the parameters of the considered element. A description of the model and methods of measuring parameters of the inductor using an impedance analyzer and a chamber for thermal measurements is given. The obtained results of measurements are compared with the results of calculations proving a satisfactory match.
The study is dedicated to the experimental and analytical determination of the parameters of the π-shape circuit models of high-frequency two-winding planar transformers used in various types of power electronic converters. For determining the winding capacitance, magnetizing and leakage inductances, waveforms of the voltage and current in the primary winding of a no-loaded and short-circuit transformer were used. The resistances of both windings for alternating current and the resistance corresponding to power losses in magnetic core were determined analytically based on Dowell's and Steinmetz's formulas, while considering the effect of temperature. The subject under consideration was a 5600 VA planar ferrite-core transformer designed for operating with a rectangular-wave primary voltage of 360 V and a frequency equal 100 kHz. Streszczenie. Pracę poświęcono eksperymentalnemu i analitycznemu wyznaczaniu parametrów modeli obwodowych kształtu π wysokoczęstotliwościowych dwuuzwojeniowych transformatorów planarnych stosowanych w różnego rodzaju przekształtnikach energoelektronicznych. Do wyznaczania pojemności uzwojeń, indukcyjności magnesującej i indukcyjności rozproszenia wykorzystano oscylogramy napięcia i prądu uzwojenia pierwotnego transformatora pracującego bez obciążenia i w stanie zwarcia. Rezystancje obu uzwojeń dla prądu przemiennego oraz rezystancję odpowiadającą stratom mocy w rdzeniu wyznaczono analitycznie na podstawie wzorów Dowell'a i Steinmetz'a, uwzględniając przy tym wpływ temperatury. Przedmiotem rozważań był transformator z planarnym rdzeniem ferrytowym o mocy 5600 VA przeznaczony do pracy przy prostokątnym napięciu pierwotnym 360 V i częstotliwości 100 kHz. (Wyznaczanie podstawowych parametrów modelu obwodowego wysokoczęstotliwościowego transformatora planarnego).
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