Upgrading six cooling tower fans saves a UK semiconductor over £30k p.a. in electricity costs and improves site maintenance.

X-FAB UK Ltd is one of the largest semiconductor makers in the UK. A clean, vibration-free environment is a top priority in semiconductor manufacturing and the company uses large quantities of air and water to maintain cleanliness. The plant has three cooling towers that produce chilled water for the manufacturing process. Each cooling tower has two fans, each driven by a 37 kW fan motor.

Originally, the fans were star-delta connected, arranged in cascade style so that they would start-up, or disconnect, one-by-one as demand varied. This meant the final fan would constantly be switching on and off, sometimes as often as every 10 minutes. With a large 37 kW motor, this would draw significant start-up current.  Additionally, whenever an odd number of fans were connected, air from the last fan would blow out through one of the other fans.

Electricity use falls by 5 percent

In a move to save energy costs, the company was advised to install variable speed inverter drives to replace the star-delta starters. This involved installation of six 37 kW ABB ACS550 general purpose  drives on the cooling tower fan motors.

With the ABB drives installed, two fans start on the first tower at 20 Hz when the building management system indicates that cooling is needed. If more cooling is required, the next two fans start at 20 Hz and then the remaining two start if there is demand for still more cooling.

Projects benefits

For maximum cooling, all six fans run together at between 20 Hz and 50 Hz. The installation cost was  £15,000, and an annual saving of £31,400 has been achieved. Further energy saving projects with ABB drives have since been carried out, enabling X-FAB to reduce electricity use by about 5 percent across the site.

A further benefit has been a reduction of maintenance costs.  These have reduced, as drive belts which previously broke at least once a month with the old system no longer do so.

Go here for open ACS550 AV drives brochure from ABB UK

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