Skip to content


Induction Motor Rotor Bar Damage Evaluation With Magnetic Field Analysis


Detection of defects in induction machine rotor bars for disassembled motors are required to evaluate machines considered for repair as well as fulfilling incremental quality assurance checks in the manufacture of new machines. Detection of rotor bar defects prior to motor assembly are critical in increasing repair efficiency and assuring the quality of newly manufactured machines. Many methods of detecting rotor bar defects in unassembled motors lack the sensitivity to find both major and minor defects in both cast and fabricated rotors along with additional deficiencies in quantifiable test results and arc-flash safety hazards. A process of direct magnetic field analysis can examine measurements from induced currents in a rotor separated from its stator yielding a high-resolution fingerprint of a rotor’s magnetic field. This process identifies both major and minor rotor bar defects in a repeatable and quantifiable manner appropriate for numerical evaluation without arc-flash safety hazards.

-S. W. Clark and D. Stevens, “Induction Motor Rotor Bar Damage Evaluation With Magnetic Field Analysis,” in IEEE Transactions on Industry Applications, vol. 52, no. 2, pp. 1469-1476, March-April 2016.

Download (2.67 MB) 17558 downloads

Advanced Rotor Bar Testing With Surface Magnetic Field Measurements


A new process of measuring the magnetic field at the surface of a rotor provides an improved method of detecting rotor bar damage for a disassembled motor. Many current methods of rotor testing lack the sensitivity to detect rotor bar defects beyond major issues such as a broken rotor bar. Measuring the magnetic field of a rotor when excited from an external source allows for the detection of a wide variety of rotor defects such as brazed connection degradation, cracked rotor bars, broken rotor bars, and casting defects. This new method of rotor testing provides advantages over many current testing techniques in testing sensitivity, recording, reporting, illustration of machine condition to the end user, and testing safety.

-S. W. Clark, “Advanced Rotor Bar Testing with Surface Magnetic Field Measurements”, in Proc. EASA Conv., Milwaukee, WI, USA, June. 2018.

Download (14.62 MB) 17509 downloads