Fibre Glass Epoxy Insulation Components
ACC Insulations manufactures precision CNC-machined fibre glass epoxy components used as critical electrical insulation in transformers, electric motors, switchgear, and motor control centres (MCCs). Our components are engineered from the highest-grade glass cloth reinforced epoxy laminates — NEMA G10, G11, FR4, FR5, and the equivalent Indian grades EPGC 201, 202, and 203 — and are machined to exact OEM engineering drawings with tolerances as tight as ±0.05 mm.
Whether you need standard profiles or complex custom shapes, our CNC fabrication facilities handle everything from single prototypes to high-volume production runs — all with documented quality records and full IEC 60893 and IS 13529 compliance.
What Are Fibre Glass Epoxy Components?
Fibre glass epoxy components — also called glass epoxy laminate parts, glass reinforced epoxy (GRE) insulators, or epoxy composite insulation — are rigid, precision-machined parts produced by cutting, milling, and drilling thermoset epoxy laminate sheets reinforced with woven E-glass cloth fabric. The epoxy resin matrix bonds multiple glass layers together, creating a composite that delivers performance no single material can match alone:
Electrically: High dielectric strength (>18 kV/mm) with
excellent arc resistance and low dielectric loss make these components reliable
insulators at medium and high voltages.
Mechanically: Tensile strength typically exceeding 300 MPa and
high compressive strength allow these parts to withstand the clamping loads,
short-circuit electromagnetic forces, and operational vibrations found in
transformers and motors.
Thermally: Depending on grade selection, these components
maintain their properties from ambient up to 180°C continuous
(Class H), making them suitable for the most demanding dry-type transformer and
motor winding environments.
Technical Specifications
| Fibre Glass Epoxy Components — Technical Data | |
|---|---|
| Material Grades | NEMA G10, G11, FR4, FR5 / IS EPGC 201, EPGC 202, EPGC 203 |
| Reinforcement | Woven E-glass cloth fabric |
| Resin System | Thermoset epoxy resin binder |
| Thickness Range | 0.8 mm – 50 mm (thicker sections on request) |
| Shape & Size | As per customer engineering drawing / DXF / CAD file |
| Machining Tolerance | ±0.05 mm (standard); tighter on request |
| Dielectric Strength | >18 kV/mm (⊥ layers); >40 kV (∥ layers) |
| Volume Resistivity | >1012 Ω·cm |
| Tensile Strength | >300 MPa (warp & fill directions) |
| Flame Resistance | UL 94-V0 (FR4 & FR5 grades) |
| Thermal Endurance | Class F — 155°C (G11, FR4) | Class H — 180°C (FR5) |
| Available Colours | Lemon Yellow, Golden Yellow, Natural, Green |
| Standards | IEC 60893, IS 13529, NEMA LI-1, UL 94-V0 |
| Applications | Transformers, Electric Motors, Switchgear, MCC Panels, Dry-Type Transformers |
Epoxy Laminate Grades: G10, G11, FR4, FR5 & EPGC Explained
Selecting the right glass epoxy laminate grade is the most important factor in long-term component performance. The grade determines thermal endurance, flame retardancy, and mechanical behaviour at operating temperature. Here is a plain-language comparison:
G10 / EPGC 201
General PurposeThe workhorse glass epoxy grade. Offers excellent dielectric strength, high mechanical rigidity, and good dimensional stability at room temperature to moderate heat. Best for ambient-temperature insulation parts where flame retardancy is not a regulatory requirement.
G11 / EPGC 202
High TemperatureEngineered for elevated-temperature environments. G11 retains a significantly higher proportion of its flexural strength above 130°C compared to G10, making it the preferred grade for stator slot wedges, Class F and Class H motor components, and dry-type transformer insulation.
FR4 / EPGC 201 FR
Flame RetardantThe most widely specified flame-retardant glass epoxy grade globally. FR4 is the UL 94-V0 rated equivalent of G10 — it self-extinguishes and does not propagate flame. Standard for switchgear panels, MCC busbar supports, phase barriers, and any application requiring fire safety compliance.
FR5 / G11-FR / EPGC 203
Premium GradeCombines G11's high-temperature performance with FR4's flame retardancy. FR5 / EPGC 203 is the premium-grade choice when both Class H thermal endurance (up to 180°C) and UL 94-V0 fire safety compliance are required simultaneously — ideal for VPI transformers and high-temperature motor terminal assemblies.
Grade Comparison at a Glance
| Property | G10 | G11 | FR4 | FR5 |
|---|---|---|---|---|
| Flame Retardant (UL 94-V0) | ✗ | ✗ | ✓ | ✓ |
| Max Continuous Temp. | 130°C | 155°C | 130°C | 180°C |
| High-Temp. Flexural Strength | Moderate | High | Moderate | High |
| Dielectric Strength | Excellent | Excellent | Excellent | Excellent |
| Thermal Class | B/F | F | B/F | H |
| Indian Standard Equiv. | EPGC 201 | EPGC 202 | EPGC 201 FR | EPGC 203 |
| Typical Use | General insulation | Motor wedges | Switchgear | VPI Transformers |
Key Electrical & Mechanical Properties
- High dielectric strength (>18 kV/mm) — sustained electrical isolation under high-voltage continuous and impulse conditions in transformers and switchgear
- Excellent arc resistance — resists electrical tracking, carbon tracking, and surface discharge that can occur in contaminated or humid high-voltage environments
- High volume resistivity (>10¹² Ω·cm) — maintains insulation integrity even under prolonged voltage stress, moisture exposure, and thermal aging
- Mechanical rigidity and compressive strength — withstands winding clamping pressure, short-circuit electromagnetic forces, and operational vibration without deforming
- Thermal stability up to 180°C — maintains mechanical properties and dimensional accuracy across the full thermal cycle life of Class F and Class H equipment
- Moisture and chemical resistance — stable dielectric performance in humid, oily, and chemically aggressive industrial environments; water absorption <0.25% by weight
- Flame retardancy (FR4 / FR5) — UL 94-V0 self-extinguishing materials that prevent flame propagation in enclosed switchgear and panel assemblies
- Dimensional stability across thermal cycling — low coefficient of thermal expansion (CTE) matching requirements of wound transformer and motor assemblies
- Long service life — thermoset epoxy matrix resists creep, cold flow, and stress relaxation that can cause premature insulation failure in metallic or thermoplastic alternatives
Design Features
- Woven E-glass fibre reinforcement — bi-directional glass cloth provides uniform mechanical properties in warp and fill directions, preventing delamination under transverse loads
- Thermoset epoxy resin matrix — cross-linked polymer provides superior adhesion between glass layers, chemical inertness, and resistance to solvent attack from transformer oils and varnishes
- Colour-coded by grade — industry-standard colour coding (yellow for G10/FR4, green for G11/FR5) enables instant grade identification on the production floor, eliminating risk of grade mix-up
- CNC-machined surfaces — precision milled and drilled surfaces with controlled surface finish reduce partial discharge inception in high-voltage insulation applications
- Lighter than metallic alternatives — glass epoxy composites are typically 60–70% lighter than equivalent steel insulation hardware, reducing overall transformer and motor assembly weight
- Inherently non-conductive — eliminates risk of accidental ground fault caused by metallic components in live-part insulation zones
- Weather and UV resistance — suitable for indoor and protected outdoor electrical enclosures with no surface degradation under UV exposure
Components We Manufacture
ACC Insulations produces a comprehensive range of precision glass epoxy insulation components for OEM electrical manufacturers:
Machined G11 or FR5 wedges that secure motor winding conductors in stator slots against electromagnetic forces during short circuits and starting.
FR4 or G10 busbar support blocks and saddle insulators maintaining required phase clearances in LT and MV switchgear panels and distribution boards.
Machined insulation boards providing isolated multi-terminal connection points in transformer terminal boxes and motor junction boxes.
Flat or formed FR4 phase barrier plates electrically isolating R, Y, B phases in switchgear enclosures, MCC panels, and motor terminal boxes.
High arc-resistance G10/FR4 plates and formed arc chute assemblies for arc interruption and extinction in contactors, circuit breakers, and isolators.
Precision-machined spacers maintaining critical conductor clearances in transformer winding assemblies and switchgear busbars.
Cylindrical and flat G11 or FR5 barriers providing HV-LV isolation in distribution and power transformers.
Machined rings and brackets supporting motor end-winding coils against axial and radial movement under motor operating conditions.
Complex 2D and 3D profiles, stepped sections, slots, holes, and contoured edges machined per customer DXF drawing or CAD model.
Applications by Industry & Equipment Type
Fibre glass epoxy insulation components from ACC Insulations serve a wide range of electrical equipment manufacturers across India:
Power & Distribution Transformers
Terminal boards, lead supports, inter-winding epoxy spacers, and HV-LV barriers for both oil-cooled and dry-type designs.
Electric Motors & Generators
Stator slot wedges (G11/FR5), phase insulation barriers, end-winding support rings, and rotor insulation components for LT and HT motors.
Switchgear & MCC Panels
FR4 busbar supports, phase barriers, arc chutes, insulating shrouds, and inter-phase barriers for LT switchgear, ACBs, MCCBs, and motor control centres.
Dry-Type & Cast-Resin Transformers
Class H FR5/G11 components for VPI (Vacuum Pressure Impregnated) and cast-resin transformer coil assemblies operating at 155°C–180°C continuous.
Industrial Electrical Equipment
Custom insulation components for OEM-specific designs in welding transformers, rectifiers, autotransformers, bus ducts, and industrial control gear.
Renewable Energy Equipment
High-performance insulation components for wind turbine generators, solar inverter panels, and energy storage converter assemblies.
Manufacturing Capabilities
ACC Insulations operates advanced CNC fabrication facilities in Nashik, Maharashtra with full in-house capability for producing precision glass epoxy machined components:
- Engineering Drawing Review & DFM Our engineering team reviews your CAD drawing or DXF file and performs Design for Manufacturing (DFM) analysis before cutting begins — eliminating costly rework.
- Material Selection & Stock Verification We select the appropriate G10, G11, FR4, FR5, or EPGC grade laminate sheet and verify dimensional and visual quality before machining.
- CNC Machining — Milling, Drilling & Routing Multi-axis CNC machining centres produce complex 2D and 3D profiles, precision holes, slots, stepped sections, and contoured edges to ±0.05 mm tolerance.
- In-Process Dimensional Inspection Critical dimensions are verified at each machining stage using calibrated gauges and coordinate measurement equipment.
- First Article Inspection (FAI) Prototypes are submitted for full dimensional and visual inspection against the drawing before volume production is released.
- Final QC & Despatch Every batch undergoes visual inspection, dimensional check, and electrical testing before packaging and despatch with full documentation.
Quality Assurance
Every fibre glass epoxy component leaving ACC Insulations undergoes systematic multi-stage quality verification against customer drawings and applicable international standards:
- Dimensional inspection — all critical dimensions verified against customer drawing using calibrated gauges, CMM, and optical measurement tools
- Electrical performance testing — dielectric withstand voltage (Hi-Pot) and insulation resistance (IR) checks on representative samples per IEC 60893
- Mechanical strength verification — flexural strength and compressive strength tested on cut sample coupons per batch
- Visual and surface inspection — 100% inspection for delamination, edge chipping, drilling burrs, surface cracks, and material voids
- Material traceability — grade, thickness, and batch records maintained for full material traceability on every order
Why Choose ACC Insulations?
- OEM-focused manufacturer — decades of experience supplying precision epoxy insulation components to transformer, motor, and switchgear OEMs across India
- Full CNC machining capability — complex shapes, profiles, and holes from customer drawings to ±0.05 mm without outsourcing
- Complete grade inventory — G10, G11, FR4, FR5, EPGC 201/202/203 in multiple thicknesses (0.8 mm–50 mm) held in stock for fast turnaround
- Prototype-to-production capability — from first-article approval on a single prototype through to high-volume repeat supply
- Documented quality records — IEC 60893, IS 13529, and NEMA LI-1 compliance with traceable batch records on every order
- Flexible batch sizes — no minimum order restrictions; we supply from prototype quantities to full production volumes with equal attention to quality
- Technical support throughout — material grade selection guidance, DFM review, and application engineering support from our experienced team in Nashik
Insulation Engineering Tools
Calculate dielectric creepage distances, thermal class requirements, and recommended material thickness for your fibre glass epoxy component application using ACC's interactive insulation design tools.
Frequently Asked Questions
Fibre glass epoxy components — also called glass-reinforced epoxy (GRE) insulation parts — are precision-machined electrical insulation used wherever high dielectric strength and mechanical load-bearing are both required simultaneously. In power transformers, they appear as terminal boards, inter-winding spacers, and lead supports. In electric motors, they form stator slot wedges and end-winding support rings. In switchgear and MCC panels, they serve as busbar supports, phase barriers, and arc chutes. They replace metallic and thermoplastic alternatives by offering superior electrical isolation, higher temperature endurance, and better mechanical strength-to-weight ratio.
G10 is the standard general-purpose glass epoxy laminate, offering excellent dielectric and mechanical properties at ambient to moderate temperatures. It is not flame retardant. G11 (EPGC 202) is a high-temperature variant that retains significantly more flexural strength above 130°C — the preferred grade for motor slot wedges and Class H transformer insulation. FR4 is the UL 94-V0 flame-retardant version of G10 — by far the most widely used grade in switchgear and electrical panels where fire safety regulations apply. FR5 (EPGC 203) is the premium grade combining G11's elevated-temperature performance with FR4's flame retardancy, rated for continuous operation up to 180°C — ideal for VPI transformers and demanding motor applications.
Yes — custom machining from customer drawings is our core service. ACC Insulations operates CNC machining centres, precision milling, drilling, and routing equipment capable of producing any 2D or 3D profile in G10, G11, FR4, FR5, or EPGC laminate to ±0.05 mm tolerance. We accept DXF, DWG, PDF drawings, or physical samples. Our process includes a DFM (Design for Manufacturing) review, prototype development, first-article inspection, and then volume production with consistent quality documentation. Both small prototype quantities and high-volume repeat production orders are handled.
Our fibre glass epoxy components achieve dielectric strength exceeding 18 kV/mm measured perpendicular to the laminate layers and greater than 40 kV measured parallel to the layers — making them suitable for medium and high-voltage insulation applications in transformers, switchgear, and rotating machines. Volume resistivity exceeds 10¹² Ω·cm. Specific values depend on material grade, thickness, and test conditions; we can provide material test certificates for your specific grade on request.
Our components use a thermoset epoxy resin binder system reinforced with woven E-glass cloth fabric. The thermoset epoxy matrix cross-links during cure, creating a rigid, chemically inert composite that does not soften or creep under thermal and mechanical load — unlike thermoplastic alternatives. The epoxy system provides excellent bonding between glass layers, high arc resistance, volume resistivity above 10¹² Ω·cm, and outstanding resistance to transformer oil, moisture, cleaning solvents, and impregnation varnishes used in motor winding processes.
ACC Insulations' fibre glass epoxy components are manufactured and tested in compliance with IEC 60893 (Specification for insulating boards of thermosetting resins for electrical purposes — industrial laminates), IS 13529 (Indian Standard for glass fabric reinforced epoxy laminates), and NEMA LI-1 (Industrial Laminated Thermosetting Products). Flame-retardant grades (FR4, FR5) additionally comply with UL 94-V0 flame classification. We also manufacture to customer-specific OEM quality plans and ITP (Inspection and Test Plan) requirements for transformer and motor manufacturers.
We supply fibre glass epoxy components in Thermal Class F (155°C continuous) using G11 or FR4 grades, and Thermal Class H (180°C continuous) using FR5 or G11-FR grades — covering the requirements of high-temperature motor windings rated IEC Class F and Class H, dry-type cast-resin transformers, VPI-impregnated transformers, and other demanding thermal environments where standard Class B (130°C) materials are insufficient.
Our standard epoxy laminate stock ranges from 0.8 mm to 50 mm thickness. This covers the vast majority of transformer, motor, and switchgear insulation component requirements. For structural insulation applications requiring sections thicker than 50 mm, we can arrange lamination of sheets or source special thick-section material on request. Please contact our team with your specific thickness and grade requirement for availability and lead time.
Request a Quote
Share your requirement — grade, thickness, drawing — and we'll respond within one business day.
- G10, G11, FR4, FR5 in stock — all thicknesses
- CNC machining to ±0.05 mm from your drawing
- Prototype to production — no minimum order
- IEC 60893 & IS 13529 compliance documented
