Insulation Classes: What They Are and How They Influence Performance

June 17, 2024

Insulation classes are a fundamental classification in the electromechanical sector for determining the thermal resistance of insulating materials used in equipment such as electric motors, transformers, and generators. Understanding the different insulation classes is essential for selecting the most suitable materials based on operating conditions and ensuring reliable and long-lasting performance.

What Are Insulation Classes?

Insulation classes define the maximum temperature at which an insulating material can be continuously subjected without experiencing significant deterioration of its electrical and mechanical properties. This classification is established by international standards such as IEC 60085 and NEMA MW 1000.

The main insulation classes are:

  • Class A (105°C)
  • Class E (120°C)
  • Class B (130°C)
  • Class F (155°C)
  • Class H (180°C)
  • Class N (200°C)
  • Class R (220°C)
  • Class S (240°C)

Each class represents a 25°C increment over the previous one, except for classes R and S, which have a 20°C increment.

Influence of Insulation Classes on Performance

Choosing the appropriate insulation class is crucial for ensuring the reliability and longevity of insulation systems in electrical equipment. A higher insulation class allows operation at higher temperatures, offering several advantages:

  1. Longer lifespan: Higher-class insulating materials, such as class F and class H, can withstand higher thermal stresses, extending the equipment’s service life.
  2. Improved performance: Higher operating temperatures enable higher power outputs and efficiencies in electric motors and transformers, thanks to the ability to use smaller conductor cross-sections and reduce losses.
  3. Size reduction: Using higher insulation classes allows for more compact equipment designs, reducing size and weight, which are crucial factors in applications such as electric vehicles.
  4. Resistance to environmental factors: High-class insulating materials often exhibit greater resistance to moisture, chemical agents, and mechanical stresses, ensuring reliable performance even in harsh environments.

Selecting Insulating Materials Based on Class

To fully leverage the advantages of different insulation classes, it is essential to select the appropriate insulating materials. Some of the most commonly used materials for each class are:

  • Class A: Cotton, silk, non-impregnated paper
  • Class E: Polyester, polyurethane, epoxy resins
  • Class B: Mica, fiberglass, alkyd resins
  • Class F: Polyimide, reinforced mica, silicone resins
  • Class H: Silicone, Teflon, Kapton, ceramic
  • Classes N, R, S: Special materials such as high-density mica, high-performance polyimides, advanced ceramics

The choice of insulating material depends not only on the required insulation class but also on factors such as compatibility with the impregnation system, necessary mechanical properties, and costs.


Insulation classes play a crucial role in determining the performance and reliability of electrical equipment. A thorough understanding of these classes and associated insulating materials is essential for designers and manufacturers in the electromechanical sector.

By choosing the appropriate insulation class and high-quality insulating materials, it is possible to create optimized insulation systems that offer high performance, extended service life, and reliability even under the most demanding operating conditions.

For more information on insulation classes and flexible insulating materials, visit the website of Guerzoni Srl, a leading company in the sector with over 30 years of experience in the production and distribution of high-quality electrical insulation solutions.

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