The Universal Motor: a Classic Machine with Evergreen Challenges in Design and Modeling

The universal motor has been used for more than one century in a variety of small rating utilizations, mainly in household appliances, thanks to its features of robustness, cheapness and simplicity of feeding and speed regulation. Nevertheless, even if it can be considered a mature component, both the increasing technological and performance requirements and the need to refine its model for operation analysis and design purposes has leaded to deepen its study till nowadays. In this paper, a comprehensive overview of the different involved aspects will be presented, among which: structures, steady state operation analysis, evaluation of equivalent circuit parameters, models for the calculation of instantaneous quantities and related harmonic distortion, efficiency figures of merit, commutation waveforms and estimation of brush wear, electronic converter feeding topologies, design methods.