Atlanta, GA-based Siemens Energy & Automation, Inc. says its Robicon Perfect Harmony Drives® has an 8-MW variable frequency drive (VFD) that operates with an output frequency of 500 Hz making it the worldÕs largest high-speed VFD.

While the basic VFD topologies have been limited to output frequencies in the 120- to 200-Hz range, Siemens has already manufactured and installed drives that operate at frequencies between 315 and 400 Hz.

The power-cell based multi-level arrangement provides a unique topology that allows operation up to 500 Hz, regardless of the VFD power rating. Tests on the VFD control were set to operate the motor in encoderless vector control with 920-Hz IGBT switching frequency, resulting in an effective switching frequency of 9.2 kHz and a sample frequency of 9.2 kHz. The test drive demonstrated very high quality waveform to the motor with low harmonic distortion. This latest VFD will be used to drive permanent- magnetic motors. Siemens says it is one of the few companies to design a VFD that can operate with these physically smaller, more efficient permanentmagnetic motors. PI Siemens Energy & Automation, www.siemens.com/drives

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