Loose Windings
If the electrical windings of the motor stator are even a little loose, the vibration level at 120 Hz will be increased. This condition is very destructive because it abrades the insulation on the wire, leading to shorted turns and eventual short circuits to ground and stator failure. In some large machines such as AC generators, loose windings will generate one-half order harmonics of the 120 Hz excitation frequency.
DLI Engineering provides products and services for Predictive Maintenance including vibration analysis instruments, monitoring and diagnostic software, and consulting for CBM programs.
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