Twin Bearingless Machine Drive Configurations With a Reduced Number of Inverters

Zhouzhou Wang, Eric L. Severson

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Bearingless motors combine torque and magnetic levitation into a single electric machine. Recent research indicates that this technology has the potential to yield a reliable, oil-free, highly-efficient, and integrated solution for industrial applications if the cost associated with the electric drive can be reduced. This paper investigates power electronic implementations that reduce the required number of inverters, and thereby reducing the drive cost. The paper targets electric machinery for significant power applications, such as compressor systems, which require active actuation in all degrees of freedom (DOF). The paper shows that by implementing the system as a twin bearingless machine configuration, with each machine using a combined winding, the number of inverters (and supporting components) can be reduced by 25% through novel connections of the winding coil groups. Nine reduced-component twin bearingless machine drive configurations are proposed, evaluated, and compared. Power electronic and control implementations are proposed and experimental results demonstrate reduced-component drives levitating a prototype twin machine and controlling machine coil currents identically to the conventional (full-cost) bearingless drive.

Original languageEnglish (US)
Pages (from-to)1130-1142
Number of pages13
JournalIEEE Transactions on Energy Conversion
Issue number2
StatePublished - Jun 1 2023
Externally publishedYes

Bibliographical note

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  • Bearingless motor
  • four degrees of freedom bearingless machine drive
  • multiphase winding
  • self-bearing motor


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