The insulation level of motors and transformers is the core index to measure their high temperature resistance, and the international standard divides the insulation level into A, E, B, F, H, each level corresponds to different temperature resistance limit and application scenarios. This article mainly explains the characteristics and practical application points of class F insulation system.
Insulation class classification and temperature resistance standard table
| Insulation Class | Maximum Allowed Temperature (℃) | Typical Application Scenarios |
| A | 80℃ | Small motors, low-load equipment |
| E | 105℃ | Medium-sized motors, ordinary industrial equipment |
| B | 130℃ | Large motors, general industrial scenarios |
| F | 155℃ | Special motors, high-load or high-temperature environment equipment |
| H | 180℃ | High-temperature industrial environments (such as metallurgy, drying equipment) |
Core difference: the higher the insulation level, the more heat-resistant the material is, which is suitable for more severe temperature environment.
1.Technical characteristics of Class F insulation system
Material composition
Class F insulation is usually made of inorganic materials such as mica, asbestos, glass yarn, etc., which are impregnated with organic adhesive (e.g., silicone resin, epoxy resin) to provide high insulation strength and thermal stability, and can maintain its performance in long-term operation at 155℃.
Temperature rise assessment standard
Nominal temperature resistance: the maximum working temperature of class F insulation is 155℃, which refers to the temperature resistance limit of the insulation material itself.
Temperature rise limit: Motor design should follow the class B temperature rise assessment standard (maximum allowable temperature rise of 80K).
Calculation formula: Actual ambient temperature ≤ 155℃ (insulation temperature) - 80K (temperature rise) = 75℃.
Significance: By reducing the temperature rise requirement and reserving safety redundancy, it can avoid accelerated aging of insulation materials due to overheating and prolong the life of the motor.
2.Application Scenarios and Precautions for Class F Insulation
Typical applications:
Spindle motors for CNC machine tools, drive motors for new energy vehicles, joint motors for industrial robots, and other scenarios with high loads and limited heat dissipation conditions.
Suggestions for use:
Ensure that the operating environment temperature is lower than 75 ℃, if the ambient temperature is high, need to strengthen ventilation or configuration of the cooling system;
Regularly check the temperature rise of the motor (can be measured by infrared temperature), to avoid long-term close to the limit temperature of 155 ℃;
Avoid the use of dust, oil, and other harsh environments, to prevent the impact of impurities on the performance of the insulating material.
3.Clarification of common misconceptions
Misconception: It is believed that Class F motors can be operated directly in 155℃ environment.
Clarification: 155 ℃ is the temperature limit of insulation materials, the actual operation needs to be combined with the temperature rise limit (B standard), the ambient temperature needs to be controlled below 75 ℃ to ensure safety margins.
4.Summary
Class F insulation systems achieve a balance between performance and reliability in industrial automation, new energy and other fields through the combination of "high temperature-resistant materials + conservative temperature rise design". Understanding its technical logic and application boundaries helps us to rationally select and standardize the use, maximizing equipment life and operational safety.