Coil & Winding Selection

Winding Design Is Critical to High-Frequency Transformer Performance

The winding system determines much more than the turns ratio.

At high switching frequencies, conductor geometry and winding arrangement directly affect:

• Copper loss
• Temperature rise
• Leakage inductance
• Parasitic capacitance
• Insulation performance
• EMI behavior

HY MFG designs winding structures around the electrical requirements of the complete power converter.

Conductor Selection

Depending on the application, winding conductors may include:

• Round copper wire
• Multiple parallel wires
• Litz wire
• Triple-insulated wire
• Foil winding
• Custom conductor configurations

Selection depends on:

• RMS current
• Switching frequency
• Available winding window
• Insulation requirements
• Temperature rise
• Manufacturing constraints

Skin Effect

As frequency increases, current distribution within a conductor becomes less uniform.

This increases the effective AC resistance of the winding.

Therefore, conductor diameter should not be selected based only on DC current capacity.

The design may require:

• Smaller parallel conductors
• Litz wire
• Foil conductors
• Optimized winding geometry

depending on the frequency and current waveform.

Proximity Effect

The magnetic fields generated by adjacent conductors can further increase AC winding losses.

Winding arrangement therefore becomes an important design variable.

HY MFG evaluates:

• Layer arrangement
• Primary/secondary positioning
• Interleaving
• Conductor geometry
• Insulation thickness

to balance efficiency, leakage inductance and insulation requirements.

Leakage Inductance & Parasitic Capacitance

Winding construction directly affects parasitic parameters.

Reducing leakage inductance may require closer coupling between windings, while minimizing interwinding capacitance may require greater separation.

These requirements can sometimes conflict.

The correct winding structure therefore depends on the topology and switching behavior of the converter.

Insulation & Isolation

For isolated power supplies, winding design must also satisfy the required insulation system.

Considerations include:

• Working voltage
• Dielectric strength
• Creepage
• Clearance
• Insulation material
• Reinforced or basic insulation
• Layer insulation

The winding structure is developed according to the applicable application and safety requirements.

Manufacturing Matters

A theoretically optimized winding design is only useful if it can be reproduced consistently.

HY MFG considers:

Electrical Design → Winding Structure → Manufacturing Process → Production Consistency

during development.

Need to optimize an existing transformer winding?

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