Foil Wound Transformers and Chokes for High-Efficiency Power Applications
Modern power systems demand components that offer low leakage inductance, high mechanical stability, and efficient thermal dissipation. Foil Wound Transformers and Chokes, manufactured by Rishab Industries, meet these critical needs for industries such as UPS manufacturing, electric vehicles (EVs), battery energy storage systems (BESS), and telecom infrastructure.
By using copper or aluminium foil windings, these transformers and chokes ensure uniform current distribution, enhanced cooling, and superior EMI performance—making them a popular choice for both low-voltage and high-current applications.
Key Highlights:
- High Current Capacity
- Suitable for Low Voltage Applications
- Mechanically Strong for Vibration Resistance
- Low Leakage Inductance
- High Capacitance Value
- Low Noise & High Reliability
- Efficient Thermal Management
- Custom Foil Widths as per Design Requirements
- RoHS & CE Compliant
- Export-Ready Solutions
Applications Across Power Systems:
- UPS Systems – Input/Output Filters
- Battery Energy Storage Systems (BESS)
- EV Chargers & Power Electronics
- Inverters and Rectifiers
- Solar Power Conditioning Units
- Telecom & Industrial SMPS
- Railway Traction and Drives
Why Rishab Industries?
✅ Our Differentiators:
- In-house foil cutting & winding machinery
- High-precision edge insulation
- ISO 9001-certified manufacturing in Pune
- RoHS & CE Certified Products
- OEM supply to UPS and EV sectors in 20+ countries
- Flexible low and medium-volume production batches
Technical Specifications
Foil Wound Transformers
| Parameter | Specification |
|---|---|
| Input & Output Voltage | As per the customer specification |
| Power Rating | 0.5 kVA to 1500 kVA |
| Phase Configuration | Single Phase / Three Phase |
| Frequency | 50 Hz / 60 Hz |
| Cooling Type | Dry Type / Air Cooling |
| Insulation Class | Class H / R |
| Conductor | Foil of Copper/Aluminium |
| Core Type | CRGO / CRNGO |
| Certification | CE, RoHS Compliant |
Foil Wound Chokes
| Parameter | Specification |
|---|---|
| Inductance Range | 0.1uH to 500mH |
| Current Range | 1Amp to 2500Amp |
| Phase Configuration | Single Phase / Three Phase |
| Frequency | 50Hz/ 60Hz |
| Cooling Type | Dry Type/Air Cooling |
| Insulation Class | Class H / R |
| Conductor | Foil of Copper/Aluminium |
| Core | CRGO / CRNGO |
| Certification | CE, RoHS Compliant |
What is Transformer Foil Winding?
Transformer foil winding is a winding technique where flat copper or aluminium foil is used instead of round or rectangular wire to form transformer and choke windings.
The foil is wound in layers with insulation placed between turns, allowing current to distribute uniformly across the conductor width.
This construction reduces eddy current losses, improves thermal dissipation, and enhances mechanical strength, making foil winding suitable for low-voltage, high-current applications where thermal stability and reliability are critical.
Why Foil Winding is Used in Transformers
Foil winding is used in transformers primarily to manage high current levels more efficiently than conventional wire winding.
The wide conductor surface helps reduce AC resistance and limits localised heating caused by skin and proximity effects.
Foil winding also improves short-circuit withstand capability and provides better heat transfer to the surrounding insulation and cooling medium. These characteristics make foil winding a preferred choice for continuous-duty and power-dense electrical systems.
Foil Winding vs Wire Winding in Transformers
| Parameter | Foil Winding | Wire Winding |
|---|---|---|
| Conductor form | Flat copper or aluminium foil | Round or rectangular wire |
| Typical application | Low voltage, high current transformers and chokes | High voltage, low to medium current transformers |
| Current handling | High current capacity due to wide conductor surface | Limited by conductor cross-section |
| Eddy current losses | Lower eddy current losses | Higher eddy current losses at high current |
| Thermal performance | Better heat dissipation and uniform temperature distribution | Heat dissipation depends on conductor packing |
| Mechanical strength | Higher mechanical rigidity under short-circuit forces | Lower mechanical rigidity under fault conditions |
| Insulation arrangement | Insulation placed uniformly between foil layers | Insulation applied around individual conductors |
| Winding size | Larger for high voltage designs due to insulation layers | More compact for high voltage windings |
| Manufacturing complexity | Requires precise foil handling and insulation placement | Simpler winding process |
| Cost considerations | Higher material and processing cost in some designs | Generally lower manufacturing cost |
| Preferred use cases | UPS, EV chargers, BESS, power electronics | Distribution transformers, high voltage applications |
Foil Wound Transformers – Design Considerations
Foil wound transformer design depends on parameters such as current rating, voltage level, insulation system, thermal class, and cooling method.
Key factors include foil thickness and width, inter-layer insulation, winding geometry, and mechanical reinforcement to handle electromagnetic forces during short-circuit events.
Foil wound transformers are commonly used in applications where stable performance under continuous load is required.
Foil Wound Chokes – Design Considerations
Foil wound chokes are designed to handle high ripple currents while maintaining low losses and controlled temperature rise.
The foil geometry allows uniform current flow and reduces hot spots, which improves reliability in power electronic circuits.
These chokes are widely used in filtering, smoothing, and EMI suppression applications across industrial and energy systems.
Frequently Asked Questions (FAQs)
What does transformer foil winding mean?
Transformer foil winding refers to the use of flat copper or aluminium foil conductors instead of round wire to form transformer windings. The foil is layered with insulation between turns, allowing uniform current distribution, lower eddy current losses, and improved thermal behaviour in high-current transformer designs.
How does foil winding work in a transformer?
In foil winding, current flows across the width of a flat conductor rather than through a circular wire cross-section. This reduces localised heating and limits proximity effects. Insulation is placed between foil layers, enabling stable electrical performance and improved heat dissipation under continuous operating conditions.
Why is foil winding preferred for high-current transformers?
Foil winding is preferred for high-current transformers because the wide conductor surface distributes current evenly and reduces AC resistance. This helps control temperature rise, improves short-circuit withstand capability, and enhances long-term reliability in applications with sustained current demand.
What are the key advantages of foil winding compared to wire winding?
Compared to wire winding, foil winding offers better current distribution, lower eddy current losses, improved thermal stability, and higher mechanical rigidity. Wire winding remains suitable for high-voltage applications, while foil winding is typically selected for low-voltage, high-current transformer and choke designs.
In which applications are foil wound transformers and chokes used?
Foil wound transformers and chokes are used in UPS systems, EV charging infrastructure, battery energy storage systems, industrial power supplies, and power electronics. These applications require efficient high-current handling, stable thermal performance, and mechanical robustness.
When is foil winding not suitable for transformer design?
Foil winding may not be suitable for very high-voltage, low-current transformers where insulation requirements significantly increase winding size. In such designs, conventional wire winding can offer a more compact and practical solution depending on electrical and space constraints.
How does foil winding help reduce losses in transformers?
Foil winding reduces losses by minimising eddy currents and improving current distribution across the conductor width. This lowers AC resistance and limits hot spots, resulting in more efficient operation and consistent thermal performance under continuous load.
Is aluminium foil or copper foil used for transformer winding?
Both aluminium and copper foil are used for transformer winding depending on design requirements. Copper foil provides higher conductivity and compact winding size, while aluminium foil offers weight and cost advantages. Selection depends on current rating, efficiency targets, and thermal limits.
Can foil wound transformers and chokes be designed for custom requirements?
Foil wound transformers and chokes can be designed to meet specific current ratings, voltage levels, insulation classes, and thermal requirements. Customisation includes selecting foil dimensions, insulation systems, and winding configurations based on the intended application and operating conditions.