Tampere University of Technology

TUTCRIS Research Portal

Effect of Multilevel Inverter Supply on Core Losses in Magnetic Materials and Electrical Machines

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Article number6980114
Pages (from-to)736-744
Number of pages9
JournalIEEE Transactions on Energy Conversion
Issue number2
Publication statusPublished - 1 Jun 2015
Publication typeA1 Journal article-refereed


The effect of multilevel inverter supply on power losses in magnetic cores and electrical machines is studied. A dynamic numerical model for the hysteresis, eddy current, and excess losses in a core lamination is first developed. By both measurements and simulations for a ring-core inductor, we demonstrate how increasing the number of inverter voltage levels decreases the iron losses when compared with traditional two-level supply. Although the switching frequency has a significant impact on the iron losses in the case of a traditional two-level inverter, using three or five voltage levels makes the losses almost independent of the switching. Finally, finite-element simulations show that similar reductions are also possible for the core losses of 150-kVA and 12.5-MW wound-field synchronous machines, in which rather low switching frequencies are typically used. Calorimetric loss measurements are also presented for the 150-kVA machine in order to confirm the significant effect of switching frequency on the core losses with two-level inverter supply.


  • Eddy currents, electrical machines, excess loss, finite-element analysis, iron loss, magnetic hysteresis, magnetic materials, multilevel converter, pulse width modulation