In high-performance electrical equipment such as transformers and electric motors, a magnetic flux shielding sheet (also known as a magnetic conductive plate) serves as an essential core base material. It plays a vital role in regulating magnetic circuit distribution, reducing magnetic leakage losses, and significantly improving equipment energy efficiency.
Today, the mainstream Class F and Class H magnetic flux shielding sheets dominate the industrial market. However, due to variations in their thermal resistance ratings, they adapt to completely different industrial working conditions. This comprehensive guide provides a detailed breakdown of their technical differences, parameter advantages, and selection techniques to help you precisely identify the right material for your project.
1. Thermal Resistance Rating: The Key Basis for Classification
The classification of Class F and Class H magnetic flux shielding sheets strictly follows the universal insulation thermal resistance standards applied in the global power industry. The core distinction lies in their maximum long-term operating temperature resistance:
- Class F Magnetic Flux Shielding Sheets: Featuring a standard temperature resistance rating of 155°C, these sheets utilize a conventional epoxy impregnation process. They serve as the mainstream, dependable model for standard industrial scenarios.
- Class H Magnetic Flux Shielding Sheets: Upgraded to an ultra-high thermal resistance rating of 180°C, these sheets undergo multiple vacuum varnish impregnations and long-term, high-temperature curing treatments. This results in stronger permeability of the insulation layer and significantly enhanced resistance to thermal aging under severe environments.
2. Key Performance & Material Comparison
Understanding the material composition and environmental tolerance is crucial to preventing premature insulation failure:
- Material Composition: Class F shielding sheets are processed under high temperature and pressure from fiberglass cloth impregnated with epoxy resin, combined with iron powder and curing agents. Class H sheets are upgraded by adding premium high-temperature resistant additives on top of the standard Class F formulation.
- Environmental Tolerance: Class F is highly optimized for indoor environments with stable, normal temperatures and adequate ventilation. In contrast, Class H exhibits outstanding resistance to demagnetization and thermal cracking, allowing it to easily tolerate extreme heat, high humidity, heavy dust, and temporary overloads.
3. Application Scenarios: Balancing Performance and Cost
To avoid over-engineering and optimize manufacturing costs, materials should be selected based on precise operational requirements:
When to Choose Class F Sheets (Cost-Effective Standard)
Class F is the preferred choice for conventional electrical equipment with a long-term operating temperature of ≤155°C and stable power loads. Typical applications include:
- Indoor dry-type distribution transformers
- General industrial servo motors
- Small and medium-power electrical machinery
This model offers excellent performance redundancy while allowing effective control over production costs.
When to Choose Class H Sheets (Severe Environment Exclusive)
Class H is strictly targeted at heavy-duty scenarios where long-term operating temperatures continuously range between 155°C and 180°C. It is vital for preventing insulation degradation and magnetic circuit shifting in demanding setups, frequently working alongside high-tier materials like GPO-3 materials, FR4 laminates, or high-density mica insulation structures.
4. Summary & Professional Procurement Advice
In professional engineering selection, there is no need to blindly pursue the highest thermal rating. For standard indoor environments and steady-state conditions under 155°C, priority should be given to Class F sheets to achieve the best cost-to-performance ratio. However, if your equipment faces continuous high-temperature overloads or severe ambient environments, upgrading to a Class H magnetic flux shielding sheet is mandatory to prevent costly failures caused by thermal aging.
As a leading specialist in thermoset composite materials and industrial insulation engineering, RDS provides customized, high-precision manufacturing for both Class F and Class H magnetic conductive plates tailored to your specific technical blueprints.
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