This 1,500 HP, 1,200 RPM AC electric motor had been undergoing monthly vibration testing, and began showing marginal readings about six months before it ultimately failed.
Bodine’s evaluation of the equipment indicated the failure was due to insulation degradation that ultimately caused a winding to short. The motor appeared to be running hot, with thermal discoloration evident on the windings, rotor core and stator iron. The drive end bearing was found to have extensive damage to its thrust face, possibly causing the high running temperatures due to the motor fighting to remain on its electrical center.
Bodine’s motor shop rewound the stator winding, restacked and rebarred the rotor assembly, fabricated a new shaft, re-babbitted the bearings and replaced the winding RTDs and heaters to return the equipment to working order.