The ‘world's largest’ high speed VFD

20 September 2008

The U.S. division of Siemens says 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.

Siemens VFD
Siemens VFD

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

Siemens says that it is the power-cell based multilevel arrangement that provides the topology allowing 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. Siemens engineers said that the test drive ‘demonstrated very high quality waveform to the motor with low harmonic distortion.’

An integrated consistency check establishes the validity of the configuration and reduces the possibility of errors even before the network has been installed. A reporting function provides mounting instructions for installation personnel and documents the system for acceptance testing and troubleshooting.

This latest VFD will be used to drive permanent-magnet motors, such as found in natural gas processing and transportation applications that require high-speed compression. Siemens claims it is one of the few companies to design a VFD that can operate with these physically smaller, more efficient permanent-magnet motors.

‘Siemens has been an engineering pioneer for over a century. This latest breakthrough demonstrates our commitment to developing new technologies to increase productivity and energy efficiency for our customers,’ says Anne Cooney, Vice President of the Power Conversion Division, Siemens Energy & Automation in the U.S.A.

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