Electric motors experience severe stresses during the start-up process. Rotor bar temperatures increase significantly, stator winding end turns expand and move against their restraints, and magnetic forces pull the rotor and stator together. Once the motor is up and running with a stable load these stresses are reduced. If your electric motor testing indicates a reduced reliability, minimize your motor starts to prevent a catastrophic failure of the rotor cage or stator windings.
For more information on electric motor maintenance, visit the PdMA Corporation Web site at www.pdma.com.