Loose rotor bars are best defined as a mechanical anomaly. They commonly result in elevated 2x line frequency vibration and may first show up on EMAX testing through increased eccentricity frequencies. MCE testing may not show early indications as there are no continuity issues on the rotor cage. If left unattended, chipping and/or shorting of the rotor laminations may occur. Excessive movement may increase chances of cracks or breaks on the end ring. Swaging (press indent of rotor bars to tighten fit) is a common corrective measure before rebarring.
For more information on the Rotor Fault Zone, visit PdMA's Fault Zone Analysis page at:http://www.pdma.com/PdMA_faultzone_rotor.php