A motor's insulation class, like its "heat resistance passport," defines the maximum operating temperature its internal insulation material can withstand. This temperature is the critical point for safe operation within the motor's expected service life (typically 20 years).
When a motor is running, current and core losses generate heat, causing the temperature to rise. Once the insulation material's heat resistance limit is exceeded, it ages rapidly, becoming brittle and losing its insulating properties, ultimately leading to a short circuit and motor burnout.
Insulation classes are categorized by letters; common ones are: A (105°C), E (120°C), B (130°C), F (155°C), and H (180°C). Higher grades indicate better heat resistance. For example, a motor with Class F insulation means its insulation system can operate at temperatures of 155°C for extended periods.
Choosing a motor with a higher insulation class isn't about operating at higher temperatures, but rather providing a greater safety margin. Under the same load, it operates at lower temperatures, lasts longer, and has significantly improved reliability. Therefore, insulation grade is one of the key indicators to measure motor performance, durability and quality.
