Automation is fighting drought in Namibia

Eco Projects was undertaking a 17 month project in Windhoek, the capital of Namibia, to alleviate a critical water shortage. Using boreholes, a deep, narrow hole made in the ground to locate water, the client pumped water to various reservoirs. This is to provide an accessible store of water for Windhoek.

To power the pump system, Rockwell Automation delivered eight Allen-Bradley Powerflex 753 low voltage AC drives, varying from 250kW to 132kW. However, to use these Variable Speed Drives (VSDs) at depths of 150-250m, the company also needed to source sine wave filters. This is why the team reached out to CP Automation, which supplies and installs a range of sine wave filters for different applications.

Sine wave filters are used where VSDs are installed with extremely long motor leads, as used with the depths of these boreholes. Due to an impedance mismatch, a portion of a high frequency wave is reflected back in the direction from which it arrived. When the reflected edges encounter other wave edges, their values add, causing voltage overshoots.

Sine filters reduce the edge steepness of the waves, meaning these edges can no longer accumulate. This prevents premature motor failure caused by damaging voltage overshoots.

“Without these sine wave filters, safety and power supply would be compromised,” explained John Mitchell, Global Business Development Manager at CP Automation. “The filters eliminate high frequency content and voltage peaks generated by the variable frequency drive, thereby reducing motor heating and extending the motor life. If these waves were not converted, voltage overshoots could have halted this incredibly important project for the Namibian community.”

“The long motor cable lengths meant the sine filters reduced parasitic capacitance,” said Carlo van Heerden, Engineering Solutions Manager of Eco Projects. “The VFDs and sine filters created a winning combination, allowing the motor to run safely at continuously adjustable speeds, with adjustable torque for varying mechanical loads.

“Working with CP Automation, and joining forces in the way we have, has meant that we could carry out this project safely and efficiently, helping the people of Namibia access reliable water supplies, with long term protection.”

CP Automation may be carrying out a second phase on the current boreholes later this year, involving the installation of harmonic filters to reduce voltage distortion and to keep transformers cool and efficient for a long time.