Efficiency Contours and Loss Minimization Over a Driving Cycle of a Variable Flux-Intensifying Machine

Takashi Fukushige, Natee Limsuwan, Takashi Kato, Kan Akatsu, Robert D. Lorenz

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)


In this paper, experimental evaluations for the efficiency of a novel interior permanent-magnet (IPM) machine with variable-flux characteristics using low-coercive-force magnets are presented. The variable-flux characteristics allow improving the efficiency of a machine. A flux-intensifying IPM type having positive saliency is employed for a positive d-axis current to mitigate a demagnetizing field in the magnet due to a q-axis current. A proof-of-principle machine is designed, fabricated, and evaluated. A series of experiments are conducted to capture the magnetization and demagnetization properties of the low-coercive-force magnets by applying control d-axis current pulse. The efficiency contours with different magnetization states (MSs)of the magnets are then experimentally obtained. The designed machine shows benefits in improving efficiency when the MS is optimally operated. With these results, the loss over a driving cycle is then simulated, and the benefits of changing the MS are quantified.

Original languageEnglish
Article number07046393
Pages (from-to)2984-2989
Number of pages6
JournalIEEE Transactions on Industry Applications
Issue number4
Publication statusPublished - 2015 Jul 1


  • Efficiency
  • flux-intensifying machine
  • memory motor
  • permanent-magnet machines
  • variable magnetization machine
  • variable-flux machine

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering


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