Air Gap Flux-Based Detection and Classification of Damper Bar and Field Winding Faults in Salient Pole Synchronous Motors

Yonghyun Park, Sang Bin Lee, Jangho Yun, Mladen Sasic, Greg C. Stone

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


Recent cases of broken damper bars and shorted field winding turns in synchronous motors (SMs) have shown that rotor faults can degrade motor performance and lead to a forced outage of the motor and driven process. However, detection of SM rotor faults has not received much attention since SMs are not as common as induction motors. Detection of SM rotor faults is difficult, as the damper bar is active only under the starting or load transients, and shorted field winding turns result only in a slight increase in rotating asymmetry. SM rotor fault testing in the field mainly relies on visual inspection or off-line tests, and new test methods that can provide reliable detection of the faults without motor disassembly is highly desirable. In this article, new test methods for not only detecting, but also classifying the two types of SM rotor faults under motor standstill and starting are proposed. A finite element and experimental study on 1.1 MW and 30 kW salient pole SMs are provided to verify the proposed methods. It is shown that damper and field winding faults can be detected and classified with high sensitivity and reliability compared to conventional tests.

Original languageEnglish
Article number9050838
Pages (from-to)3506-3515
Number of pages10
JournalIEEE Transactions on Industry Applications
Issue number4
Publication statusPublished - 2020 Jul 1

Bibliographical note

Funding Information:
Manuscript received December 2, 2019; revised February 19, 2020; accepted March 24, 2020. Date of publication March 29, 2020; date of current version July 1, 2020. Paper 2019-EMC-1494.R1, presented at the 2019 IEEE Energy Conversion Congress and Exposition, Baltimore, MD, USA, Sep. 29–Oct. 3, and approved for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Electric Machines Committee of the IEEE Industry Applications Society. This work was supported by the Korea Government (MSIT) through the National Research Foundation of Korea (NRF) under Grant NRF-2019R1A2C1084104. (Corresponding author: Sang Bin Lee.) Yonghyun Park and Sang Bin Lee are with Korea University, Seoul 02841, South Korea (e-mail:; sangbinlee@

Publisher Copyright:
© 1972-2012 IEEE.


  • Air gap flux
  • damper bar
  • fault diagnostics
  • field winding
  • off-line testing
  • salient pole synchronous motor (SM)
  • search coil
  • spectral analysis
  • starting transient

ASJC Scopus subject areas

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


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