OKI Electric Cable Develops the World’s First Ultra Small Micro-Surge Suppressor for Inverter-Fed Motors

“We are very excited about this revolutionary method that enabled us to make the micro-surge suppressor ultra small. The surge suppression wire technology and the energy regeneration module, which includes a delay circuit and a rectifier circuit, are based on OKI Electric Cable’s advanced technology for designing noise-resistant cables, and on the studies of Professor Toshihisa Shimizu at Tokyo Metropolitan University,” said Takashi Hattori, President of OKI Electric Cable. “We believe we can apply this method not only to surge suppression but also as to other noise countermeasures.

Compared to the conventional method, which employs electric filters, this new suppressor reduces power consumption to a minimum (lower than one-thirtieth), and size to less than one-eightieth with 15KW power motors. In addition, more than 90% of the micro-surge noise can be suppressed. Sales of “eco Surge μ” are planned to start in July 2009 worldwide. OKI Electric Cable will showcase this suppressor at TECHNO-FRONTIER 2009 (EMC Japan 2009), which will be held from April 15-17 at Makuhari Messe in Japan (Booth number: 5421).

As machine tools become higher in precision and faster to operate, the speed of inverter switching is also becoming faster. In addition, by applying higher power voltage to improve power efficiency, micro-surge, which is induced by impedance mismatch, also increases. This can cause malfunctions in the peripheral circuits and have adverse effects on inverter-fed motors. Such effects include insulation deterioration in motor coils, which damages the motor.

For these countermeasures, conventionally, LC filter circuit had been inserted between the inverter and drive-wire that slows down the surge rise on drive signal waveform and dissipates the surge energy as heat. However, with this method, as the motor power increased, it was necessary to use expensive and large sized high-power-rated capacitors and coils. Thus, the space requirement, price and increased power consumption for suppression had been problems.

OKI Electric Cable had developed a surge suppressor based on surge suppression cable and energy regeneration technology which was significantly smaller in size than conventional filters. To reduce the size even more, OKI Electric Cable jointly developed this new suppressor with Tokyo Metropolitan University. By efficiently returning only the surge energy to the inverter input, the two groups succeeded in developing a surge suppression method with minimal (less than one-thirtieth compared to conventional filters) power consumption for suppression.

This new method does not require high-power-rated capacitors or coils. The “eco Surge μ” consumes less power to suppress surges, thus less heat is generated. By adjusting the delay-circuit constants of the energy regeneration module, more than 90% of the micro-surge noise can be suppressed and reused as power.

The “eco Surge μ” can be placed in areas where conventionally it could not due to limited space in the switchboard. In addition, it can be used in a wide range of applications such as energy savings for inverter-fed motors.
Going forward, OKI Electric Cable will enhance its noise-resistant products and focus on developing leading-edge technologies to respond to a broad range of customer needs.