Step-up transformers are critical equipment in power systems, with the core function of converting low voltage to high voltage. They are widely used in photovoltaic grid connection, wind power generation, energy storage systems, and high-voltage transmission. As the core material for step-up transformer windings, the selection of copper foil directly affects the transformer’s conversion efficiency, temperature rise characteristics, and operational reliability.
I. Operating Characteristics of Step-Up Transformers and Copper Foil Requirements
1.1 Operating Characteristics
Compared with ordinary distribution transformers, step-up transformers have the following significant characteristics:
- High voltage level: Output voltage typically above 10kV, some can reach 500kV and above
- Large transformation ratio: Low primary voltage and high secondary voltage with large turns ratio
- Strict insulation requirements: High voltage windings require thicker insulation and larger electrical clearance
- Leakage magnetic control: Precise control of leakage magnetic flux and stray losses
- High frequency characteristics: Some step-up transformers operate at frequencies above power frequency (such as photovoltaic inverter side)
1.2 Core Considerations for Copper Foil Selection
| Technical Points | Requirements |
|---|---|
| Conductivity | IACS≥101%, reduce operating losses |
| Thickness Accuracy | Tolerance within ±3% |
| Insulation Matching | Match with insulation system, ensure electrical clearance |
| Surface Quality | Smooth and defect-free, ensure insulation integrity |
| Thermal Class | Operating temperature 120-180°C |
II. Technical Specifications of Copper Foil Materials
2.1 Recommended Grades and Characteristics
| Grade | Copper Content | Conductivity | Tensile Strength | Elongation | Typical Applications |
|---|---|---|---|---|---|
| C11000 (ETP) | ≥99.90% | ≥101% IACS | 200-280 MPa | ≥15% | Standard Step-up Transformer |
| C10100 (OFC) | ≥99.99% | ≥101.5% IACS | 190-260 MPa | ≥20% | High-Performance |
| C10200 (TPA) | ≥99.95% | ≥101% IACS | 195-265 MPa | ≥18% | Precision Electronics |
2.2 Key Performance Parameters
Electrical Performance:
- Conductivity: IACS≥101% (annealed)
- Resistivity: 0.01724 Ω·mm²/m (20°C)
- Temperature Coefficient: 0.00393/°C
Geometric Dimensions:
- Thickness Range: 0.05-3.0mm
- Thickness Tolerance: ±0.02mm (high precision) or ±0.05mm (standard)
- Width Range: 10-600mm
Mechanical Properties:
- Tensile strength: 200-280 MPa (annealed)
- Elongation: ≥15-25%
- Hardness: 35-65 HV
- Surface roughness: Ra≤0.8μm
III. Special Process Requirements for Step-Up Transformers
3.1 High Voltage Winding Insulation Design
- Copper foil and insulation paper matching: Nomex paper, polyester film composite insulation
- Oil channel design: Layer oil channel width must meet both heat dissipation and insulation requirements
- Electrical clearance: Distance from copper foil edge to core ≥5mm (high voltage side)
- Creepage distance: Sufficient creepage distance design at winding ends
3.2 Skin Effect Control
High frequency step-up transformers (such as photovoltaic inverters) need to consider skin effect:
- Skin depth calculation: Approximately 9.3mm at 50Hz, approximately 0.93mm at 1000Hz
- Copper foil thickness selection: When operating frequency exceeds 100Hz, copper foil thickness is typically ≤1.5mm
- Proximity effect: Winding arrangement must consider additional losses caused by proximity effect
3.3 Winding Process Parameters
| Process Parameters | Recommended Values | Explanation |
|---|---|---|
| Winding Tension | 10-20 N/mm² | Adjust according to copper foil condition |
| Winding Speed | 20-60 m/min | According to equipment capacity |
| Annealing Temperature | 400-650°C | Soften copper foil |
| Insulation Baking | 120-180°C | Cure insulation layer |
IV. Industry Standards and Certification System
| Standard System | Standard Number | Scope of Application |
|---|---|---|
| IEC | IEC 60325 | Copper Foil for Transformers |
| IEC | IEC 60076 | Power Transformer General Requirements |
| GB | GB/T 5231 | Processed Copper and Copper Alloys |
| ASTM | ASTM B152 | Copper Sheets, Strips, and Foils |
| JIS | JIS H3100 | Copper and Copper Alloy Strips and Foils |
V. Quality Inspection and Control
5.1 Incoming Material Inspection
| Inspection Items | Testing Methods | Judgment Standards |
|---|---|---|
| Chemical Composition | Spectroscopic Analysis | Cu≥99.90% |
| Mechanical Properties | Tensile Test | Tensile strength and elongation meet standards |
| Thickness Tolerance | Thickness Gauge | ±0.02mm (high precision) |
| Surface Quality | Visual + Microscope | No cracks, inclusions, oxidation |
| Conductivity | Eddy Current Conductivity Meter | IACS≥101% |
5.2 Common Defects and Hazards
| Defect Types | Manifestations | Potential Hazards |
|---|---|---|
| Thickness Inconsistency | Thickness fluctuation along coil direction | Localized excessive temperature rise |
| Surface Scratches | Mechanical damage traces | Insulation layer punctured |
| Edge Burrs | Sheared edges not smooth | Damage to insulation paper |
| Oxidation Discoloration | Copper foil turns black/green | Increased contact resistance |
VI. Supplier Selection Recommendations
6.1 Core Capability Assessment
- Full-process production line: Melting → Hot Rolling → Cold Rolling → Annealing → Slitting
- Thickness control accuracy: Within ±0.02mm
- Testing equipment: Spectrometer, thickness gauge, tensile machine, conductivity meter
- Certification: ISO 9001/14001/45001
6.2 Technical Service Capability
- Provide material reports and dimensional inspection reports
- Support small batch sampling
- Non-standard customization (thickness, width, condition)
- Timely technical support response
6.3 Production Capacity and Delivery
- Monthly production capacity: ≥200 tons
- Standard specifications: 7-10 days delivery
- Customized specifications: 15-20 days delivery
VII. Product Specifications (Reference)
| Grade | Thickness (mm) | Width (mm) | Temper | Tensile Strength (MPa) | Conductivity (IACS) |
|---|---|---|---|---|---|
| C11000 | 0.1-2.5 | 20-500 | O/H22/H24 | 200-280 | ≥101% |
| C10100 | 0.05-2.0 | 10-400 | O/H22 | 190-260 | ≥101.5% |
| C10200 | 0.1-3.0 | 20-600 | O/H24 | 195-265 | ≥101% |
Surface Condition: Bright/Natural
Packaging: Wooden crate + moisture-proof paper + iron sheet packing, suitable for sea freight export
Conclusion
The selection of copper foil for step-up transformer windings requires comprehensive consideration of voltage level, operating frequency, insulation matching, and cost-effectiveness. It is recommended to focus on thickness control accuracy, testing capabilities, and technical service response speed during supplier evaluation.
Our company has focused on exporting electrical wire and metal foil for 30 years and can provide C11000/C10100/C10200 series copper foil for step-up transformers, supporting customized sizes. Samples can be shipped worldwide. Inquiries are welcome.
Contact Information:
Email: office@cnlpzz.com
WhatsApp: 0086-19337889070
The technical parameters described in this document are general reference values. For specific selection, please consult with our technical team to confirm the step-up transformer design requirements.