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. Quick Technical Comparison Breakdown
To help engineering and procurement teams quickly evaluate both options, here is a direct comparison breakdown between Class F and Class H magnetic conductive sheets:
| Feature | Class F Shielding Sheet | Class H Shielding Sheet |
|---|---|---|
| Max Operating Temp | 155°C (Class F Insulation) | 180°C (Class H Insulation) |
| Impregnation Process | Standard epoxy matrix resin impregnation | Multiple vacuum varnish impregnations & high-temp curing |
| Thermal Overload Capability | Moderate, suitable for stable steady-state loads | Exceptional anti-aging & temporary overload tolerance |
| Recommended Working Conditions | Well-ventilated, indoor stable environments | Severe heat, high humidity, heavy dust, or heavy-duty setups |
| Cost & Application Focus | High cost-efficiency for dry transformers & standard motors | Premium choice for severe environment equipment protection |
4. 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.
5. 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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