A direct procedure for selecting DC motors fed from solar arrays based on curve fitting techniques

This paper suggests a new and more direct procedure for selecting the motor type and magnetic parameters yielding optimal matching with photovoltaic solar arrays. It is based on combining both the maximum power locus of the solar array and the motor´s voltage-current characteristics, assuming a perfect match at all radiation levels. It will then be possible to derive the required (ideal) flux-current relationship of the DC motor. In other words, the matching problem will be reduced from the usual analysis in the voltage-current plane to the mapping of the motor´s ideal magnetic characteristic on a new plane relating the motor flux and its armature current. From this curve, through the application of simple curve fitting, the appropriate type and magnetic parameters of the motor can then be easily determined. As will be seen from the different case studies, the results will depend on the solar array parameters, the motor´s total armature circuit resistance, as well as on the torque-speed curve of the mechanical load.