As electric vehicles (EVs) are continuously moving towards higher power density, higher speeds, and better efficiency, thermal management of power electronics and traction motors has become a key engineering challenge. As high-speed motors run above 10,000 RPM and power electronics produce considerable heat, traditional solid conductors are failing to keep up. This is where rectangular Litz wire comes in—a technology that is changing how the industry thinks about both electrical losses and thermal performance.

Litz wire, which consists of multiple insulated strands twisted or braided together, greatly decreases AC losses due to skin and proximity effects—which become more significant at high frequencies. Although traditional round Litz wire has been commonly used, the rectangular version has specific advantages, especially in EV applications.

An additional "heat" advantage of flat Litz wire is that it dissipates heat faster. Rectangular Litz wire can also increase the filling ratio due to the removal of the gaps between the strands and the cross-sectional shape is more compact by around 20% in comparison with round based designs. This more tightly packed arrangement results in better thermal contact with the surrounding cooling systems. As one industry analyst observes, the larger cross-sectional area enhances the dissipation of heat along the length of the wire through surface contact and allows greater flow of current at a reduced temperature of operation. hofer technology’s patented Form Litz Wire (FLW) winding technology proves that superior winding design allows better thermal conductivity, more effective heat dissipation to the cooling system and higher continuous motor performance.

rectangular Litz wire, not only good for the thermal advantages but also for outstand electrical performance. The rectangular shape allows slot fill factors of between 45% and 65% for stator windings, which is far superior to the 35% to 45% obtainable with round Litz wire arrangements. This higher copper density is a direct result of the higher power density and better space utilization.

The loss reduction is equally amazing. Studies show that hybrid rectangular Litz wire winding can reduce AC loss up to 34% over solid hairpin designs. hofer technology validation testing has proven up to a 25% reduction in electric motor losses making possible lighter, smaller, more efficient traction motors. At higher speeds where high-frequency losses dominate Litz - wires also exhibit a pronounced advantage over solid .

The automotive litz wire market segment is growing significantly with increasing numbers of rectangular profiles being used for specialized applications with demand for high current carrying capability and high EMC performance. From EV traction motors and inverters to wireless charging systems and on-board chargers, rectangular litz wire is emerging as a critical enabler of next-generation electric mobility.As the automation industry continually strives for higher efficiency, power density and thermal management, the rectangular litz wire technology appears as the one that satisfies all these requirements, and is considered as one of the building bricks of the future EV powertrain.