Allen-Bradley PowerFlex low voltage drives powering pump motors at depths of 150 metres and more.

Rockwell Automation sub-Saharan Africa was contracted by Eco Projects, a Rockwell Automation Namibian systems integrator, for equipment to power borehole pumps in Windhoek,

Namibia. The borehole development is the first phase of 17-month plan designed to alleviate the critical water supply shortage experienced by the City due to southern Africa’s current drought conditions.

Rockwell Automation’s scope of work was to engineer and deliver eight Allen-Bradley PowerFlex 753 low voltage AC drives varying from 250 kW to 132 kW.

The PowerFlex drives are needed to automate the pump systems that transfer water from the boreholes to various reservoirs in the municipal area.

“To make sure our drives could safely and adequately power the submersible pumps installed at depths of 150 to 250 metres, we made use of CP Automation, a global member of the Rockwell Automation PartnerNetwork, to engineer the correct sine filters.

The VFD and sine wave filter combination allows the motor to run at continuously adjustable speeds and the torque is adaptable to varying mechanical loads,” says Pieter Briel, Industry Account Manager, Rockwell Automation. “Due to the significant cable length from the PowerFlex 753 drives to the motors, it was necessary that sine filters also be installed to reduce the parasitic capacitances that result from such long cables lengths and result in reactive power.”

The Rockwell Automation order was placed in the latter part of October 2016 and delivery took place during November. Eco Projects was responsible for total electrical installation including construction of switchboards, installation and commissioning. Six boreholes were commissioned in December 2016.

 “Providing the equipment quickly and to spec enabled our systems integrator to successfully implement the project within the three-month designated period.

They had excellent support from suppliers, local engineering consulting firms and other supporting contractors,” Briel concludes. “As a result Eco Projects has received the order to install an additional five boreholes, with the commissioning date set for March 2017.”   The additional borehole pumps will be fitted with the same Rockwell architecture, although the variable speed drives will range from 132 kW to 160 kW.