Surge suppressor

Japanese researchers at OKI Electric Cable and Tokyo Metropolitan University have developed a new method to suppress micro-surge, an over-voltage noise that occurs when an inverter switches an AC waveform into a series of digital pulses. 

Conventionally, an LC filter circuit inserted between the inverter and motor drive-wire slowed down the rise time on the signal waveform to the motor and dissipated the surge energy as heat.

However, with this technique, as the motor power increased, it was necessary to use expensive and large-sized high-power rated capacitors and coils for the task.

Now, however, the researchers at OKI Electric Cable claim that their new supression technology – based on the use of surge-suppression cable and energy regeneration techniques – is significantly smaller in size, and less expensive than conventional filters.

In use, only the surge energy from the driver pulse train to the motor is returned to the inverter via an energy regeneration module that comprises delay circuitry and a rectifier.

As such, the new method does not require high-power rated capacitors or coils and consumes less power than conventional techniques used to suppress surges.

By adjusting the delay-circuit constants of the energy regeneration module, more than 90 per cent of the micro-surge noise can be suppressed and reused as power.

Sales of a new product – the eco Surge µ – which is based on the theory, are planned to start in July 2009 throughout the world.