Rotor Overheating

Problem: Overheating of the rotor can lead to loss of insulation life, shorting of turns, and eventual ground faults. Overheating usually has it roots in problems with the original design or abnormal operating conditions. Localized heating often can be found at the body to retaining ring interface. The photo at the top left shows the location of darkened areas on the rotor surface, which are typical of overheating caused by abnormal operation. In other cases, short-term overheating results from blocked ventilation passages caused by shifting insulation components or slot wedges.