VFDs reach milestone

Siemens has achieved a new record with the world’s largest high-speed variable frequency drive.
By Plant Engineering Staff August 18, 2008

Siemens Energy & Automation Inc. has announced its Siemens Robicon Perfect Harmony Drives have reached a technical milestone with the introduction of a 8 MW variable frequency drive (VFD) that operates with an output frequency of 500 Hz, making it the world’s largest high speed VFD.

This milestone is just the latest for the series of high-speed Siemens Robicon Perfect Harmony drives. 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 Siemens Robicon Perfect Harmony power-cell based multilevel 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. This 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, such as those found in natural gas processing and transportation applications that require high-speed compression.