WEG's new MVW01 range, available in southern Africa from Zest WEG, is setting a new standard for medium-voltage (MV) variable frequency drives (VFD), achieving market leading efficiency of 99%. This is as a result of a design that employs high voltage (6,5 kV) IGBTs to minimise component levels and a multi-level topology to reduce harmonic currents to extremely low levels.

Great Basin Gold's Burnstone Mine recently saw the first local installation of this advanced VFD on the African continent and several other projects have since followed suit by specifying the WEG MVW01, including Sasol South Africa (compressor), Konkola mine Zambia (mills), Boteti kimberlite mine Botswana (mill)and Bibiani gold mine Ghana (pumps).

The WEG MVW01 (seen here) meets what are considered the optimum requirements of a MV drive system and this includes high efficiency, low manufacturing costs, small physical size, high reliability, effective fault protection, easy installation, self-commissioning and minimum downtime.

Zest has developed specialised software for mill applications for frozen charge protection. The software can be customised for specific applications and after detecting a frozen charge will automatically abort the operation preventing damage to the mill. Automatic release of the frozen charge is also possible, if required.

The WEG MVW01 drives incorporate new generation technology such as plastic film capacitors in the DC link, user-friendly interface and programming, and state-of-the-art protection features. The semi-conductor component count is the lowest on the market as a result of the technology applied and notably there is no series-connection of semi-conductors. These two factors ensure reliability and efficiency. The input transformer provides galvanic isolation from the supply, offering protection to both the VSD and the motor. The input transformer need only be a 12 pulse shift transformer, with dual secondary winding.

This creates the positive aspects of galvanic isolation and harmonic mitigation. In addition to exceptional reliability - with an MTBF (mean time between failures) exceeding 22 years - and several technological advancements, the WEG MVW01 is backed up by experienced local technical teams on hand at short notice and locally available spares. In addition, it has also been designed to ensure that maintenance is extremely quick and simple.

The WEG MVW01 is available up to 6 000 KW in 3,3 kV or 4,16 kV and will shortly also be available in 6,6 kV. A compact version up to 750 KW is part of the range, allowing input switchgear, shift transformer and inverter to be incorporated in a single unit. These drives are compact and extremely robust, suitable for the tough operating conditions encountered across the spectrum of South African industry. The WEG MVW01 is ideal for high-demand applications, such as mining, cement, shipping, iron metallurgy and petro-chemical.