16 October 2013 – Zest WEG is progressing toward the hot commissioning phase of the biggest medium voltage (MV) variable speed drive (VSD) unit ever supplied by its holding company, the WEG group, worldwide. The equipment was ordered from WEG Germany by the Linde group, which is involved in a project at Sasol. Linde’s order comprised a 9.0 MVA 18 pulse phase shift transformer, a 6.5 MW 4,160 V MVW01 VSD and a 6.5 MW 4P 4,000 V MGF 800 L motor to run a production-critical compressor at Sasol.

The shipment arrived on site in the third quarter of 2011. The MVW01 range achieves 99% efficiency as a result of a design that employs multi-level topology using 6.5 kV integrated gate bipolar transistors (IGBTs) that minimise component levels. The output also utilises optimal pulse pattern (OPP) space vector modulation (SVM) which reduces motor harmonic currents to extremely low levels.

The MVW01 is designed to control MV induction motors, and these drives incorporate new generation technology such as plastic film capacitors in the DC link.

The input transformer provides isolation from the supply, offering protection to both the VSD and the motor. The input transformer needs only be a 12 pulse shift transformer with dual secondary winding. This creates the positive aspects of galvanic isolation and harmonic mitigation without the negative aspects of some complex multi-pulse designs.

The WEG MVW01 has a mean time between failures (MTBF) exceeding 22 years.