In winding insulation analysis, which sign indicates overheating may have occurred?

• A. Discoloration or odors and a drop in insulation performance
• B. Uniform insulation color
• C. Higher insulation resistance
• D. No change in appearance or performance

Answer: (B)

Overheating in windings wears the insulation material, causing physical and electrical symptoms. When insulation gets too hot, it can darken or develop burnt odors as the materials break down, and its dielectric properties deteriorate, leading to lower insulation resistance and other signs of degraded performance. That combination—color change or odor plus a drop in insulation performance—is the clearest indicator that overheating may have occurred.

The other possibilities don’t signal overheating. A uniform insulation color suggests no visible damage from heat. Higher insulation resistance implies healthy insulation rather than overheating, and no change in appearance or performance means nothing abnormal is detected.