How can flat wire transformers significantly improve power conversion efficiency by reducing winding resistance?
Publish Time: 2025-11-03
With the rapid development of modern power electronics technology, power conversion efficiency has become a core indicator for measuring equipment performance. Whether it's the drive system of new energy vehicles, the inverter of photovoltaic power generation, or the power supply modules of high-frequency switching power supplies and data centers, transformers, as key components for energy transmission and voltage transformation, directly affect the overall system's energy efficiency level due to their losses. Copper loss is one of the main losses in transformers. Traditional transformers mostly use round enameled wire windings, which suffer from low conductor utilization and high resistance. Flat wire transformers, with their unique rectangular conductor structure, demonstrate a revolutionary advantage in improving power conversion efficiency by significantly reducing winding resistance.1. Structural Optimization: Increasing Slot Fill Rate and Effective Conductor AreaThe most fundamental advantage of flat wire transformers lies in the design of their conductor shape. When traditional round wire is wound, due to geometric characteristics, triangular gaps inevitably exist between the conductors, resulting in a slot fill rate that is typically only 60%~70%. This means that nearly one-third of the space is occupied by insulating varnish and air, failing to be used for conduction. Flat wire transformers use rectangular or flat-section copper conductors with surface contact between adjacent wires, arranged closely with almost no gaps. This structure can increase slot fill factor to 80% or even 90% or more, significantly improving the copper packing density per unit volume. Under the same volume or number of turns, flat wire windings have a larger effective conductor cross-sectional area, laying the physical foundation for reduced resistance.2. Reduced DC Resistance: Directly Reduced Copper LossesWith the number of turns and magnetic circuit length remaining constant, the larger the conductor cross-sectional area A, the smaller the DC resistance R of the winding. Since flat wire transformers achieve a larger conductor cross-sectional area within a limited space, which is proportional to the resistance, the significant reduction in resistance directly leads to a substantial decrease in copper losses. For example, this advantage is particularly prominent under high-current conditions, such as in the windings of new energy vehicle motors or charging pile power modules, not only improving system efficiency but also reducing energy waste and heat generation.3. Suppressing High-Frequency AC Losses and Optimizing Dynamic PerformanceIn high-frequency applications, the skin effect and proximity effect cause current to concentrate on the conductor surface, resulting in AC resistance much higher than DC resistance, further increasing losses. Flat wire transformers address this challenge through various technical means:Multi-strand parallel winding or segmented design: Large-section flat wire is divided into multiple narrow-width conductors wound in parallel, with the width of each conductor controlled within the skin depth range to effectively suppress the skin effect.Optimized winding arrangement: Interlayer staggered winding, Z-shaped winding, or segmented windings are used to reduce magnetic field interference and lower eddy current losses caused by proximity effects.Uniform current distribution: Flat wire has a large contact area, resulting in more uniform current distribution, avoiding localized overheating, and improving the equivalent conductivity at high frequencies.4. Enhanced heat dissipation capacity, maintaining efficient and stable operationFlat wire windings have a larger contact area with the core, frame, and cooling medium, resulting in a shorter heat conduction path. Heat can be transferred more quickly from the inside of the conductor to the surface and then dissipated through insulation materials or cooling systems. Good heat dissipation performance results in lower temperature rise of the transformer under high load, preventing further increase in copper resistance due to temperature rise, thus maintaining stable output with low losses and high efficiency. This is especially important for industrial equipment operating at full load for extended periods.5. High Mechanical Strength, Supporting Automated ProductionThe flat wire structure offers greater rigidity and a more compact winding, effectively resisting vibrations and deformations caused by electromagnetic forces, reducing partial discharge and increased losses due to loosening. Simultaneously, flat wire facilitates pre-forming and automated winding, improving production consistency and yield, ensuring each transformer consistently meets design efficiency targets.Through its unique rectangular conductor structure, the flat wire transformer achieves a higher slot fill factor and a larger effective conductor cross-sectional area, fundamentally reducing the DC resistance of the windings. This physical advantage directly translates into significant reductions in copper losses and improvements in power conversion efficiency. In applications with extremely stringent energy efficiency and space requirements, such as new energy sources, electric vehicles, and 5G communication power supplies, flat wire transformers have become a key technology for improving overall system performance.
