Epoxy cast transformers are the mainstream product of dry-type transformers, using epoxy resin as insulation and casting material to completely encapsulate copper foil windings in the epoxy resin system. Compared with oil-immersed transformers, epoxy cast transformers have significant advantages including fire prevention, explosion-proof design, easy maintenance, and suitability for harsh environments. They are widely used in high-rise buildings, subways, factories, and power systems.
As the core material for epoxy cast transformer windings, copper foil compatibility with epoxy resin, electrical performance, and mechanical strength directly affect the transformer’s insulation class and service life.
I. Technical Characteristics and Copper Foil Requirements
1.1 Operating Characteristics
- Excellent insulation: Dense insulation structure after epoxy resin curing
- Fire and explosion proof: Oil-free design, suitable for high fire safety requirements
- Moisture resistant: Suitable for humid and salt spray environments
- Easy maintenance: Maintenance-free, high operational reliability
- Low noise: Small vibration of core and windings
1.2 Role of Copper Foil in Epoxy Casting
- Conductive function: Carries load current
- Support function: Forms composite structure with epoxy resin
- Heat dissipation: Transfers heat to resin and core
1.3 Core Selection Considerations
| Technical Points | Requirements |
|---|---|
| Surface Condition | Clean, oil-free, good adhesion with resin |
| Thickness Accuracy | Tolerance within ±3% |
| Surface Roughness | Ra≤0.8μm |
| Conductivity | IACS≥101% |
| Purity | Low impurity content |
II. Technical Specifications
2.1 Recommended Grades
| Grade | Purity | Conductivity | Tensile Strength | Elongation | Application |
|---|---|---|---|---|---|
| C11000 (ETP) | ≥99.90% | ≥101% IACS | 200-280 MPa | ≥15% | Standard Epoxy Cast |
| C10100 (OFC) | ≥99.99% | ≥101.5% IACS | 190-260 MPa | ≥20% | High-Performance |
| C10200 (TPA) | ≥99.95% | ≥101% IACS | 195-265 MPa | ≥18% | Precision Applications |
2.2 Key Performance Parameters
Electrical: Conductivity IACS≥101% (annealed), Resistivity 0.01724 Ω·mm²/m (20°C)
Dimensions: Thickness 0.3-3.0mm, Tolerance ±0.02mm, Width 20-600mm
Mechanical: Tensile strength 200-280 MPa, Elongation ≥15-25%, Hardness 35-65 HV, Surface roughness Ra≤0.8μm
III. Epoxy Casting Process and Copper Foil Matching
3.1 Process Flow
- Pre-treatment: Cleaning, degreasing, drying
- Winding: Form copper foil into windings
- Preheating: Preheat windings to appropriate temperature
- Vacuum casting: Inject epoxy resin under vacuum
- Curing: Heat cure to form insulation layer
3.2 Surface Treatment Requirements
| Treatment | Purpose | Requirement |
|---|---|---|
| Degreasing | Remove oil contaminants | No oil residue |
| Drying | Remove moisture | Moisture content ≤0.05% |
| Surface roughening | Improve adhesion | Light micro-etching |
| Anti-oxidation | Prevent oxidation | Short-term protection |
IV. Industry Standards and Certifications
Standards: IEC 60325, IEC 60076, GB/T 19282, GB/T 5231, ASTM B152
Certifications: ISO 9001, UL, RoHS/REACH, SGS
V. Quality Inspection
5.1 Inspection Items
| Inspection | Method | Standard |
|---|---|---|
| Chemical Composition | Spectroscopy | Cu≥99.90% |
| Thickness Tolerance | Precision Gauge | ±0.02mm |
| Surface Quality | Visual | No scratches, oil, oxidation |
| Conductivity | Eddy Current | IACS≥101% |
| Surface Roughness | Profilometer | Ra≤0.8μm |
5.2 Compatibility Testing
| Test | Method | Requirement |
|---|---|---|
| Adhesion Test | Peel Test | ≥1.0 N/mm |
| Heat Resistance | Aging Test | 130°C/1000h no delamination |
| Electric Strength | Breakdown Test | ≥20 kV/mm |
VI. Supplier Selection Recommendations
- Full-process production line (melting → rolling → annealing → slitting)
- Thickness control accuracy: ±0.02mm
- Surface treatment capability: degreasing and drying available
- Complete testing capabilities including compatibility testing
- ISO 9001/14001/45001 certified
VII. Product Specifications
| Grade | Thickness | Width | Temper | Conductivity |
|---|---|---|---|---|
| C11000 | 0.3-3.0mm | 20-600mm | O/H22/H24 | ≥101% IACS |
| C10100 | 0.3-2.5mm | 20-500mm | O/H22 | ≥101.5% IACS |
| C10200 | 0.3-3.0mm | 20-600mm | O/H24 | ≥101% IACS |
Conclusion
The selection of copper foil for epoxy cast transformers requires focus on resin compatibility, surface cleanliness, and dimensional accuracy.
Our company has 30 years of experience exporting electrical wire and metal foil. We provide C11000/C10100/C10200 series copper foil for epoxy cast transformers with customized sizes and global sample shipping.
Contact:
Email: office@cnlpzz.com
WhatsApp: 0086-19337889070
The technical parameters described are general reference values. Please consult our technical team for specific selections based on your epoxy cast transformer design requirements.