Minimization of Active Part Cost of a 100 kVA Distribution Transformer Using Exhaustive Search Method

Abstract: This paper addresses the optimum transformer design problem to minimize the active part cost of three phase core type distribution transformer. The transformer design process involves substantial heuristic exercise to select the design, best suited to a set of specifications. The design problem considers minimization of total cost of core and conducting material, while constraints are imposed on no load losses, total losses and percentage impedance as they are very critical to all day efficiency, overall efficiency and voltage regulation of a transformer. A MATLAB program has been developed which calculates all dimensions and performance parameters of 4080 transformer designs, out of which, the design having the minimum cost, satisfying the manufacturing specifications, BEE standards and constraints is selected. The transformer dimensions and performance parameters are compared with the transformers made by Jyoti Transelect Company, Bhuj, (India) and necessary changes are suggested in transformer dimensions to obtain optimal design

Keywords: Design Optimization, Active part cost minimization, Distribution transformer, MATLAB

NOMENCLATURE List of Symbols

Q kVA rating of transformer Φm Maximum flux in core (webers) AT Number of ampere turns NLV Number of turns in LV or secondary winding NHV Number of turns in HV or primary winding VLV Voltage of LV winding VHV Voltage of HV winding Et Volt per turn Ag gross core area (sq.cm) Bm Maximum flux density in core (Wb/m2) Kg Stacking factor dc Core diameter (cm) Cw Core weight (kg) Clc Core limb centre (cm) Hw Window height (cm) Wds Width of largest stamping (cm) δCL Density of core material (gm/cm3) Alw Weight of aluminium winding (kg) δAL Density of aluminium (gm/cm3) MDLV Mean diameter of LV winding (mm) MDHV Mean diameter of HV winding (mm) ALV Cross sectional area of LV (sq.mm) AHV Cross sectional area of HV (sq.mm) LLHV Load losses in HV (watts) LLLV Load losses in LV (watts) NLLsp Specific no load losses (watts/kg) NLL No load loss (watts) We Exciting power (VA/kg) Im Magnetizing component of no load current (A) Iw Core loss component of no load current (A) I0 No load current (A) Asl Average stack length of LV and HV coil (mm) RBHV Radial build of HV winding (cm) RBLV Radial build of LV winding (cm)