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Direct savings on first 'Direct-to-Drive'

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As part of its Pinjarra refinery efficiency upgrade, Alcoa World Alumina Australia has contracted Rockwell Automation Australia to provide 12 variable speed drives (VSD) for new mud transport pumps, to be installed throughout the plant.

The new PowerFlex 7000 medium voltage VSDs with Direct-to-Drive technology will be installed at a rate of two per month over six months.

Driven by increased demand for high-quality alumina, the Pinjarra upgrade is aimed at improving the refinery's throughput by around 600,000 tonnes of alumina per annum.

"One part of the overall upgrade is the installation of these new pump VSDs," said Scott Southby, product manager, medium voltage, Rockwell Automation Australia. "Alcoa selected the PowerFlex 7000 because they're the most efficient and cost effective models for slurry pumping applications."

Eight 500kW and four 355kW PowerFlex 7000 3,300 volt VSDs are being installed for three different types of applications: mud-to-washer transport pumps, mud booster pumps and repulp tank pumps. While the VSD provides for a more efficient form of pumping with significant energy savings, the PowerFlex 7000 was also chosen for its small footprint and ease of maintenance.

According to Southby, this order represents the first in the region for Rockwell Automation's unique Direct-to-Drive technology.

"Usually, all drives of this type require an isolation transformer to reduce harmonics and mitigate common mode voltage stress generated by variable frequency drives," he said.

"This new design eliminates that requirement allowing the footprint to be reduced by 40 per cent with no compromise on quality."

The elimination of the isolation transformer also means that efficiency is increased while wiring, componentry, and subsequent installation costs are reduced.

Additionally, the PowerFlex 7000 VSD with Direct-to-Drive technology carries no special motor requirements--which means that any standard motor (new or existing) can be connected.

This decreases the cost of the overall system and makes the whole range of PowerFlex 7000 Direct-to-Drive technology ideal for all standard and specialty industrial and commercial applications.

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