Low-frequency eddy current testing using HTS coil driven by PWM inverter

Teruyoshi Sasayama, Keiji Enpuku

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


When testing ferromagnetic materials such as iron, low-frequency eddy-current testing (LF-ECT) is used to avoid the skin effect. However, the drawback of LF-ECT is that the signal becomes weak at low frequencies. Furthermore, when the specimen is covered with protective materials, the signal becomes even weak, owing to the large lift-off. To overcome these drawbacks, we utilize a high-temperature superconducting (HTS) coil and a pulse-width modulation (PWM) inverter in the LF-ECT method. Using an HTS coil and a PWM inverter, strong currents are conducted, and the change in the coil resistance can be easily measured. The small impedance change of the HTS coil is detected by using a Maxwell bridge. The result demonstrates that a steel plate thickness of up to 20 mm can be estimated based upon the measurements of the change in the coil resistance, even when the lift-off is 98 mm.

Original languageEnglish
Pages (from-to)1275-1282
Number of pages8
JournalInternational Journal of Applied Electromagnetics and Mechanics
Issue number4
Publication statusPublished - 2019

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Electrical and Electronic Engineering


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