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As solid-state transformers become increasingly important in renewable energy, electric vehicles, smart grids, and fast-charging infrastructure, SST-Litz Wire has become one of the key winding materials for achieving higher power density, lower losses, and better thermal performance.
SST Leeds wire is a specialized, modified type of Leeds wire designed specifically for the high-frequency, high-voltage, and pulsed operating conditions characteristic of solid-state transformers (SSTs). This wire is not a general-purpose RF Leeds wire; rather, it is a customized winding wire exclusively for the high-voltage power conversion field in power electronics, offering exceptional suitability for these specific operating conditions. In the fields of smart grids, high-voltage conversion for new energy, and wide-bandgap semiconductor power equipment, traditional winding wires can no longer meet the demands of high-frequency operation.
SST Leeds Wire, relying on an optimized conductor structure, insulation system, and transposition process, addresses the core pain points of traditional wires: high high-frequency losses and susceptibility to insulation breakdown. It is a high-precision, multi-layer, fully cross-linked insulated conductor—a significantly upgraded version of traditional Leeds wire designed for high-frequency conversion scenarios in medium- and high-voltage power electronics. Most traditional Leeds wires are only suitable for low-voltage, low-power, low-pulse civilian RF equipment, offering extremely low operational redundancy. In contrast, SST Leeds wire fully aligns with industrial-grade design specifications for high-voltage, high-frequency power equipment in terms of structural design, material selection, and manufacturing standards.
Unlike standard high-frequency Litz wires on the market, SST Litz wire features systematic insulation optimization specifically tailored for wide-bandwidth alternating pulses, nanosecond-level steep-front voltages, and high-frequency harmonic superposition conditions. Conventional wire insulation systems can only withstand power-frequency sinusoidal voltages and are unable to accommodate the non-sinusoidal, high-steepness, and frequently fluctuating SST voltage waveforms. The SST’s specialized insulation structure effectively disperses pulsed electric field stress, eliminating high-frequency faults such as transient high-voltage breakdown, inter-strand creepage, and partial discharge. General-purpose Leeds wires are primarily used in low-voltage, low-power applications such as communications RF, small sensors, and low-frequency signal transmission.
All SST Litz wire base conductors are made entirely of ultra-high-purity, micron-level oxygen-free copper single strands, with strand diameters precisely matched to the equipment’s operating frequency. Custom strand diameters are designed for different frequency bands ranging from 20 kHz to 1 MHz to ensure full compliance with high-frequency skin depth thresholds. This eliminates engineering issues such as excessive high-frequency losses and imbalanced current distribution caused by improper wire diameter selection.
All monofilament diameters are strictly smaller than the high-frequency current skin depth at the corresponding operating frequency, meeting the core engineering criteria for high-frequency wire design. This physical structural design completely eliminates the skin effect phenomenon, where current accumulates on the surface of individual wires while the center remains unloaded. It allows the entire cross-sectional area of each copper wire to fully participate in current conduction, maximizing the utilization of the conductor’s effective cross-sectional area.
Compared to ordinary thick copper wires or conventional stranded wires of the same cross-sectional area, the ultra-fine multi-wire structure can significantly reduce the additional power losses caused by the high-frequency skin effect. Under high-frequency operating conditions, the advantages of this structure are amplified exponentially, significantly outperforming traditional monolithic conductor structures. This provides a solid conductor foundation for high-frequency transformers to operate with low temperature rise, high efficiency, and long service life.
The surface of each ultra-fine copper wire is treated with a precision coating process, uniformly applying a modified polyimide insulating varnish film that is resistant to high temperatures and pulse surges. The varnish film is uniformly thick, free of pinholes, thin spots, or buildup defects, and its insulation consistency far exceeds that of ordinary wire. The proprietary insulation varnish formulation has been specifically modified and optimized for high-frequency switching pulses in wide bandgap devices.
Once formed, the insulation layer on each individual wire can reliably withstand ultra-steep pulse voltage spikes of the 100 V/ns order during SST equipment operation. It effectively disperses transient pulse electric field stress, eliminating faults such as inter-strand partial discharge, creepage, and arc breakdown. It ensures long-term insulation isolation between multi-strand wires, preventing inter-strand short-circuit failures.
Unlike ordinary bare stranded wire and semi-insulated stranded wire—which suffer from structural defects due to the lack of complete inter-strand insulation—SST Leeds wire achieves full insulation protection for each individual strand. This completely eliminates partial discharge issues caused by strand-to-strand potential differences under high-frequency operating conditions, significantly enhancing the durability of coil insulation. This is also one of the core structural advantages of SST Litz wire for high-voltage, high-frequency pulse applications.
Multiple independently insulated individual wires are first bundled according to standard pitch to form a structurally uniform base sub-bundle unit. Subsequently, multiple groups of these sub-bundles undergo secondary and tertiary layered composite stranding to form a multi-level symmetrical composite conductor structure. The multi-layer stranding process is strictly controlled at every stage to ensure the overall structure is uniform, with consistent tension and free of localized looseness or defects.
A systematic alternating forward-reverse transposition process is employed throughout, causing each individual wire to continuously cycle between inner and outer positions along the entire length of the wire. This completely resolves the structural drawbacks of conventional Litz wire, where the magnetic field environments of inner and outer strands are inconsistent. It ensures that the electromagnetic induction conditions for all individual strands are fully uniform, achieving highly consistent electrical performance.
This high-precision symmetrical interleaving structure effectively eliminates magnetic field differences and induced electromotive force deviations between wire bundles. It balances the induced voltage and current of each strand at the structural level, achieving a natural and even distribution of current. This minimizes high-frequency proximity losses to the greatest extent possible, ensuring stable and consistent electromagnetic performance of the coil.
After all multi-stage precision stranding processes are completed, the entire outer layer of the wire is coated with a high-strength composite insulation protective layer or a wire-wrapped protective layer. This outer protective structure significantly enhances the wire’s overall mechanical resistance to tensile, compressive, and bending forces. This effectively prevents wire damage that may occur during automated winding, embedding, and shaping processes.
The outer insulation material has undergone specialized modification to provide excellent resistance to high temperatures, hydrolysis, high-frequency aging, and damp heat. It is perfectly suited for the harsh operating conditions of solid-state transformers’ sealed high-temperature chambers and enclosed heat dissipation environments. Long-term operation will not result in issues such as insulation powdering, cracking, peeling, or aging-related failure.
| Name | Litz wire |
| Conductor | Copper |
| Single wire dimension | 0.01 ~ 1.00mm |
| Numbers of strands | 5~10000 (odd or even optional) |
| Standard | According to customer’s requirement |
| Insulation material | Polyamide，Polyester ,Polyurethane,etc |
| Packing | Ply wooden spool or according to customer’s requirement |
| Application | SST transformer,RF transformers,RF tranceivers,Sensors,Ballasts,etc. |
All performance advantages of SST Litz wire are precisely tailored to the complex operating conditions of solid-state transformers, including high-frequency operation, pulse surges, and dynamic load variations. It specifically addresses core industry pain points associated with traditional wires, such as high high-frequency losses, rapid insulation aging, excessive temperature rise, and poor reliability. It is currently the core supporting material for enhancing the energy efficiency and reliability of high-frequency solid-state transformers.
Engineering test data shows that SST Leeds wire can effectively reduce the overall copper losses in high-frequency transformers by 30%–60%. It significantly improves the overall power conversion efficiency of solid-state transformers and reduces grid operating energy consumption. It fully meets the current standards for high energy efficiency, low losses, and low-carbon operation in smart grids. The higher the operating frequency, the more severe the skin effect and proximity losses in traditional wires become, and the more pronounced the decline in energy efficiency. SST Leeds wire maintains stable, low-loss characteristics across an ultra-wide frequency range, perfectly aligning with the SST’s wide-band dynamic operating mode. It meets the diverse operational requirements of equipment, including frequency modulation, load modulation, and varying operating conditions.
SST Leeds wire employs a specially modified pulse-resistant insulation system capable of withstanding high-frequency, steep-rising pulse voltages generated by wide-bandgap devices over the long term. It effectively suppresses minute partial discharges between coil turns and strands, preventing micro-arcs from continuously eroding the insulation layer. This ensures the insulation structure remains intact, stable, and free from degradation over the long term. The insulation systems of standard, general-purpose Leeds wires are only suitable for low-frequency, low-voltage applications and are highly prone to aging under high-frequency pulsed conditions involving SiC and GaN. Long-term operation can lead to layer-by-layer powdering, cracking, and peeling of the insulation, ultimately causing short-circuit breakdown failures.
Relying on a high-precision, multi-level symmetrical transposition structure, SST Litz wire ensures equal current shunting and consistent load distribution across each individual wire. There are no adverse conditions such as single-point current overloads or localized load concentrations within the wire. The overall current distribution is highly uniform, resulting in a more stable electromagnetic operating state for the coil.
SST Litz wire features a multi-strand, ultra-fine-wire composite structure, offering overall flexibility and bending toughness far superior to solid copper wire and coarse stranded wire. It is perfectly suited for the manufacturing processes of high-frequency transformers, including automated tight winding, multi-layer stacking, and precision winding of irregularly shaped coils. It is ideal for industrial-scale, high-volume precision production, delivering high yield rates and excellent processing stability.
SST Leeds wire reduces coil heating at the source due to its extremely low high-frequency losses, enabling the entire unit to operate with minimal temperature rise. Combined with a modified insulation system rated for temperatures above 200°C, it offers exceptional thermal stability. It can operate stably over the long term inside the sealed, high-temperature transformer cavity, where heat dissipation is limited.
