Ronald Coutu (Committee Member), Marian K. Kazimierczuk (Advisor), Sayiu Ren (Committee Member), Ronald Riechers (Committee Member), Raymond E. Siferd (Committee Member)
Doctor of Philosophy (PhD)
The scope of this research is concentrated on analytical winding size optimization (thickness or diameter) of high-frequency power inductors wound with foil, solid-round wire, multi-strand wire, and litz-wire conductors.
The first part of this research concerns analytical optimization of the winding size (thickness or diameter) for the inductors conducting a sinusoidal current. Estimation of winding resistance in individual inductor layers made of foil, taking into account the skin and proximity effects is performed. Approximated equations for the winding power loss in each layer are given and the optimal values of foil thickness for each layer are derived.
A low- and medium-frequency approximation of Dowell's equation for the multilayer foil winding is derived and analyzed. A new closed-form equation for the optimum foil thickness at which the global minimum of the winding ac resistance occurs is derived and an equation for the foil winding hill thickness at which the local maximum of the winding ac resistance is obtained is given.
An analytical optimization of solid-round-wire windings conducting a sinusoidal current is performed. New closed-form analytical equations are derived for the normalized valley diameter, normalized hill diameter, and normalized critical diameter.
An approximate model for multi-strand wire winding, including litz-wire winding is presented. The proposed model is evaluated using Dowell's equation. The model takes into consideration the existence of proximity effect within the litz-wire bundle, i.e., between the strands as well the skin effect. New closed-form analytical equations are derived for the normalized strand diameter to achieve the local minimum of the ac winding losses for sinusoidal current.
The second part of this research concerns analytical optimization of the winding size (thickness or diameter) for the inductors conducting harmonic currents with and without dc offset. Analytical winding power loss minimization of foil inductors conducting ac harmonic currents with and without dc offset is presented.
Equations for the optimum foil thickness of inductors operating with multi-harmonic ac currents and equation for the optimum foil thickness of inductors operating with multi-harmonic ac currents superimposed on the dc current are derived.
The design procedure for the foil inductor with optimized foil thickness is presented for a pulsewidth-modulated (PWM) dc-dc boost converter operating in discontinuous conduction mode (DCM).
An analytical optimization of solid-round-wire windings conducting both the dc and ac non-sinusoidal periodic currents is performed. Closed-form analytical equations for the normalized total-power-valley diameter and the normalized total-power-critical diameter are derived for inductors conducting ac non-sinusoidal periodic currents superimposed on the dc component. A design procedure of the inductor with an optimized winding diameter operating in PWM dc-dc buck converter in DCM is also presented.
Experimental verification of an analytical equations for foil, solid-round-wire, and litz-wire windings conducting sinusoidal currents is performed. Likewise, experimental verification of an analytical equations for foil and solid-round-wire winding inductors operating in PWM dc-dc power converters conducting non-sinusoidal periodic currents is also performed.
Department or Program
Department of Computer Science and Engineering
Year Degree Awarded
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