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Surface Rotor Magnetic Field Analysis (SRMFA)

SRMFA is a new process of measuring the magnetic field at the surface of a rotor which 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.

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

Rotor Bar Defect Offline Test Methods

Electrical Safety
Automatic Analysis
Effective on All Rotors
Major Defect Detection
Minor Defect Detection
Human Interpretation
Potential Motor Damage
Contamination Potential
Modifications Required