Contributed by ALL-TEST Pro
Soft Foot occurs on machines when the feet of the machines and the platform they are mounted on are not on the same plane. In electric motors, soft foot distorts the frame, which in turn, can distort the stator magnetic field.
This creates unbalanced electrical forces between the rotor and the stator magnetic field. These faults are often diagnosed by vibration personnel as unequal air gaps or static eccentricity by users of Electrical Signature Analysis (ESA).
Static soft foot is best checked using a dial indicator to determine the amount of soft foot and feeler gauges to determine the type of soft foot. Dynamic soft foot requires a more detailed method of testing.
Soft foot in motors can lead to premature bearing failure and loose or broken rotor bars. Electrical Signature Analysis quickly and easily identifies static and dynamic soft foot. Static soft foot can be detected using the de-energized Motor Circuit Analysis Dynamic test mode.