Heavy slot bar markings on an electric motor may indicate?

Heavy slot bar markings on an electric motor are indicative of electrical overload. When an electric motor experiences electrical overload, the currents flowing through its windings can exceed the motor's designed capacity. This excessive current can cause the rotor bars, often referred to as slot bars, to show unusual wear patterns or markings due to overheating and increased magnetic stresses.

In this condition, the thermal effects of the overload can lead to distortion or degradation of the rotor material, leaving noticeable markings. These markings can vary in appearance, but they commonly indicate that the motor has been subjected to conditions beyond its safe operational limits, which can significantly affect its performance and lifespan. Monitoring these indicators is crucial for maintenance personnel to ensure the longevity and reliability of electric motors.