FR4 Epoxy Sheet Applications and Selection Guide for Transformers

Time: 09-13 2025 Auther: Xujue Electrical

1. Applications of FR4 Epoxy Sheets in Transformers FR4 epoxy glass fiber laminates are high-performance composite i...

1. Applications of FR4 Epoxy Sheets in Transformers

FR4 epoxy glass fiber laminates are high-performance composite insulation materials with high mechanical strength, excellent electrical insulation, good heat resistance, and flame-retardant properties.

In transformers, they are mainly used for:

Coil Frames and Supports

To support windings, keep coils stable, and prevent vibration or displacement.

Interlayer and Phase Insulation Boards

Placed between coil layers or phases to provide reliable electrical insulation.

Busbar/Lead Supports and Insulation Plates

To secure busbars, leads, and other conductive components while preventing partial discharge.

Heat-Resistant and Flame-Retardant Areas

Used in high-temperature zones to maintain dimensional stability and prevent deformation or burning.

fr4 epoxy sheet applications in transformer

2. Selection Criteria for FR4 Epoxy Sheets

When selecting FR4 sheets, the following factors should be considered:

Selection Factor	Description
Electrical Properties	Dielectric strength, insulation resistance, and arc resistance must meet transformer design requirements.
Mechanical Properties	Tensile, flexural, and impact strength to ensure safe operation and transportation.
Heat Resistance	Typically Class B (130℃) or Class F (155℃), chosen according to temperature rise.
Flame Retardancy	UL94 V-0 rating to ensure fire safety.
Machinability	Ease of cutting, milling, stamping, or laser processing.
Thickness & Dimensions	0.3mm–50mm; thinner for insulation sheets, thicker for structural supports.

3. Application and Selection Reference Table

Application	Function	Selection Recommendation	Typical Thickness
Coil Frame	Supports windings and maintains stability	High mechanical strength, heat resistance Class B/F	3–20mm
Interlayer Insulation	Electrical insulation between coil layers	High dielectric strength, UL94 V-0	0.3–3mm
Phase Separator	Insulation between phases	Excellent dielectric performance, flame-retardant	0.5–5mm
Busbar/Lead Support	Supports busbars and leads	High mechanical strength, good machinability	2–10mm
Heat Shield	Protection in high-temperature zones	High heat resistance, dimensionally stable	5–20mm
Insulation Barrier	Prevents partial discharge	High insulation resistance, flame-retardant	0.5–10mm

4. Summary of Selection Guidelines

High voltage levels → Choose FR4 sheets with high dielectric strength and appropriate thickness.

High-temperature environment → Choose Class B or F heat-resistant material.

High flame-retardant requirements → Choose UL94 V-0 rated material.

High mechanical support requirements → Consider sheet thickness and strength.

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