Automated monitoring of magnet quality for permanent-magnet synchronous motors at standstill

Jongman Hong, Doosoo Hyun, Sang Bin Lee, Ji Yoon Yoo, Kwang Woon Lee

Research output: Contribution to journalArticlepeer-review

73 Citations (Scopus)


Demagnetization of permanent magnets (PMs) used in synchronous motors can occur due to a combination of thermal, electrical, and/or environmental operating stresses. Since PM demagnetization results in degradation of motor performance, efficiency, and reliability, it is important to monitor the quality of PMs regularly. However, there are many limitations to the offline and online methods currently used for magnet quality assessment. In this paper, a new inverter-embedded technique for automated monitoring of magnet quality for permanent-magnet synchronous motors (PMSMs), which overcomes the limitations of existing techniques, is proposed. The main concept is to use the inverter to perform a standstill test whenever the motor is stopped to detect local or uniform PM demagnetization. The machine is excited with a pulsating field at different angular positions, and the change in the current peaks caused by the change in the degree of magnetic saturation due to demagnetization is observed. An experimental study on a 10-hp PMSM verifies that local and uniform PM demagnetizations can be detected with high sensitivity.

Original languageEnglish
Article number5464380
Pages (from-to)1397-1405
Number of pages9
JournalIEEE Transactions on Industry Applications
Issue number4
Publication statusPublished - 2010 Jul


  • AC machine
  • NdFeB magnet
  • condition monitoring
  • demagnetization
  • diagnostics
  • inverter
  • offline testing
  • permanent magnet (PM)
  • pulsating magnetic field
  • synchronous motor

ASJC Scopus subject areas

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


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