Oki Electric Cable and Fanuc Ltd. annnounced that the two companies have succeeded in developing a motor drive cable based on their proprietary cable structure that significantly reduces the impact of conducted noise caused by inverter switching. Compared to conventional servomotor drive cables, the newly developed cable (Product name: Symmetric Motor Drive Cable ‘SYM Series,’ with joint patent pending in Japan and overseas) can double the recovery efficiency of conducted noise current. Sales of the new product start now.

“We are pleased to unveil the new non-shielded motor drive cable jointly developed by OKI Electric Cable and Fanuc. With our proprietary cable structure, we succeeded in achieving an industry-first, high recovery rate of conducted noise current by making the inductance of the earth cable small,” says Takashi Hattori, President of OKI Electric cable. “We always take environmental conservation activities seriously and are developing products that do not contain hazardous substances. So for example, this cable bans all six subject substances in Europe’s RoHS Directive.”
As inverter switching speeds become faster, conducted noise tends to increase as well. Conventional cables have low noise current recovery efficiency because the earth cable impedance is large, making it likely that peripheral equipment may malfunction due to conducted noise. To avoid this, in general, thick earth cables or several earth cables are connected in parallel or braided wired and shield cables are adopted. However, such cables are hard and their external diameter is thick. Moreover, coating of the shields can be costly and can degrade the installation characteristics because it adds another step for coating.

The “SYM Series” achieves a noise current recovery efficiency that is equivalent to a shielded cable by reducing the earth cable inductance to the same level as a shielded cable. While the cable is a maximum of 15% thinner and 20% lighter than a shielded cable, the noise current recovery efficiency is equivalent. Because the SYM Series eliminates the need for shielding, which adds another step when fabricating cable terminals, the cable offers increased flexibility and significantly improves the laying and installation characteristics.

By making the impedance of the earth cable and each dimension of the motive power line small, noise effect will become small. OKI Electric Cable succeeded in doing this by balancing the three centers of the earth cable and motive power line, without using a shield. In addition, by bringing the cables close and reducing the size of the earth cable’s impedance, the noise effect becomes small.

Established in 1936, Oki Electric Cable Co., Ltd. provides various advanced communications cables, optical cables, and related electronic parts and equipment to the worldwide market. As a member of the OKI Group, Oki Electric Cable Co., Ltd. plays a major role in the group, with the sales of more than 13 billion yen. For more information, please visit the Oki Electric Cable website at

• http://www.okidensen.co.jp/english/e_home.htm