GPO-3 vs G10 vs FR4: Key Differences, Properties & Application Selection Guide

Key Differences Between GPO-3, G10, and FR4 and How to Select the Right Material In electrical equipment, transforme...

Key Differences Between GPO-3, G10, and FR4 and How to Select the Right Material

In electrical equipment, transformers, switchgear, and industrial machinery, the performance of insulation materials directly affects the safety and reliability of the system. GPO-3, G10, and FR4 are three commonly used insulation materials. Due to differences in their composition and properties, they are suitable for different applications.
This guide explains their core differences and provides clear selection recommendations.

1. Material Overview and Composition Differences

GPO-3 (Glass Polyester – Moulding Sheet)

Base Material: Glass fiber reinforced unsaturated polyester resin
Features: UL94 V-0 flame retardant, excellent arc resistance, high tracking resistance, medium-high mechanical strength
Manufacturing Method: Mold-pressed sheets (thick, dimensionally stable, not easy to deform)

G10 (Glass Epoxy – Non-Flame Retardant)

Base Material: Glass fiber cloth + pure epoxy resin
Features: Extremely high mechanical strength, excellent moisture resistance, but non-flame-retardant
Standard: NEMA G10

FR4 (Glass Epoxy – Flame Retardant)

Base Material: Glass fiber cloth + epoxy resin + flame-retardant additives
Features: High mechanical strength, good electrical properties, UL94 V-0 flame retardant.
Considered the flame-retardant upgrade of G10.
Most widely used: PCB, motors, generators, transformers, etc.

2. Core Performance Comparison

3. Typical Applications

GPO-3 Applications

Suitable for structural insulation parts requiring stable electrical properties and strong arc resistance:
Switchgear internal insulation barriers & partitions
Busway phase barriers and separators
Transformer end plates and coil press plates
Electrical enclosure insulation components
Railway, elevator, and industrial control cabinet insulation parts
Keywords: Flame-retardant + Arc-resistant + Structural parts

G10 Applications

Ideal for applications requiring extremely high mechanical strength without mandatory flame-retardant requirements:
Mechanical fixtures, jigs, precision supports
Aerospace components
Insulation parts for high-humidity environments
Motor end caps and support rings (non-FR)
Keywords: High mechanical strength + No flame-retardant requirement

FR4 Applications

The most common choice where both flame retardancy and high electrical performance are required:
PCB boards
Generator insulation barriers, stator/rotor slot wedges
Transformer spacers, supports, insulation blocks
Motor end caps and structural insulation components
Precision machined insulation parts
Keywords: Flame-retardant + High strength + High electrical insulation

4. How to Select the Right Material (Quick Guide)

If flame retardancy is required 
Choose FR4 or GPO-3
High strength needed → FR4
High arc resistance / thick sheets → GPO-3
If extremely high mechanical strength is needed but no FR requirement →
Choose G10
For switchgear or busway systems →
GPO-3 (best arc resistance and cost-effective)
For generators or transformers →
FR4 (stable electrical & thermal performance)
For high-humidity environments →
G10 or FR4

5. Material Selection From a Machining Perspective

Summary

GPO-3 = Best for switchgear & busway structural insulation (Flame-retardant + Arc-resistant)
G10 = Highest mechanical strength, non-FR (Mechanical parts specialist)
FR4 = Most universal high-strength flame-retardant insulation board (Motors/transformers general use)

Select manufacturer

XUJUE ELECTRICAL  is a professional manufacturer of high-quality electrical insulation materials, integrating the research and development, production and sales of electrical and electrical insulation materials. It has more than 65 years of manufacturing experience. The production capacity and market share of insulation materials are ranked top three in the industry, and special insulation materials are ranked first. Products are exported to Europe, America, Southeast Asia and other countries and regions.

If you need to know more about GPO-3,FR4,G10 epoxy  sheets and other insulation materials product information and quotations, please contact us, we can mail you samples for your testing.