Sumitomo Advances Development & Manufacturing of Its Rectangular Magnet Wire for EVs

Sumitomo Electric of Japan has established a new company in China that it plans to be a major manufacturer of rectangular magnet wire beginning in 2020. Meanwhile, the company is continuing its technical development of the innovative product foreseeing its role as a key enabler for lighter, more powerful motors in the growing electric vehicle market. 

Compared to a round wire, a rectangular magnet wire can be wound without gaps in the same space, helping reduce the size and increase the output of motors. 

Sumitomo highlights the new company in the latest issue of its corporate magazine, id, and provides some details about their plans for building a substantial, global business venture based on its rectangular wire, adding to its existing portfolio of magnet wire products. 

“The demand for driving motors for electrified vehicles is expected to increase further due to the development and widespread use of hybrid vehicles and electric vehicles,” the company says. “To meet the global demand, Sumitomo Electric Wintec Magnet Wire (Changzhou) Co., Ltd. in Changzhou, Jiangsu Province, China, was established on March 21, 2019. The company will go into full operation in 2022 as one of the new global manufacturing companies for in-vehicle rectangular magnet wires. 

With a history of more than 100 years in the manufacture of magnet wires, Sumitomo Electric started manufacturing them in 1916. It started production outside Japan early to accommodate overseas customers. Sumitomo Electric Wintec (Thailand) Co., Ltd., established in 1969, was Sumitomo Electric’s first manufacturing base outside Japan. The Wintec business unit at one time operated a plant in the USA but it was closed in 2008. 

Sumitomo Electric magnet wires 

Further technical advancements by Sumitomo continue. One of the problems with magnet wire in electric vehicles is that a surge current caused by a high-voltage inverter-drive motor system can damage the insulation of the magnet wire. However, in a recent technical paper in the company’s April SEI Technical Review, “Rectangular Magnet Wire for Electric and Hybrid Electric Inverter-Drive Motors”, Sumitomo researchers describe their development of magnet wire that has a uniform micro-closed cell structure in the insulation film which offers excellent dielectric properties. 

Partial discharges occur, causing deterioration of the insulation film and shortening the voltage life for the motor. In order to suppress the partial discharges, the magnet wires are coated with a low-permittivity film. 

Conventional magnet wire with microcellular coating 
Newly developed magnet wire with microcellular coating 

“We have developed a new technology to uniformly create closed microcells in the film on a magnet wire and have succeeded in developing an innovative low-permittivity magnet wire, which has been confirmed to show excellent dielectric characteristics,” say the researchers. Permittivity is a value that shows the polarizability of an insulator. When the relative permittivity is low, the partial discharge inception voltage is high. The new technique creates many microcells in the film on a magnet wire and succeeds in developing an innovative low-permittivity magnet wire with dielectric characteristics surpassing those of conventional magnet wires, they conclude. 

Essex Furukawa rectangular magnet wire 

Rectangular magnet wire is also produced by Essex Furukawa Magnet Wire Europe GmbH, a joint venture between Furukawa Electric Co., Ltd. of Japan and US-based Superior Essex. Its high-voltage rectangular magnet wire took first place in the powertrain category of the 2017 Magna Innovation Award. Developed by Furukawa, it is an enameled rectangular wire that is coated with a PEEK (polyetheretherketone) extruded engineering plastic. 

With 335 manufacturing sites and 96 product development, engineering, and sales centers in 28 countries, Magna is a leading global automotive parts supplier. The awards are held annually to recognize its leading suppliers. 

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