The newly developed WEG 11 kV variable-speed drive (VSD) – which forms part of WEG Automation Africa’s new MVW3000 product line – is particularly suited to retrofit applications, notes WEG Automation Africa projects and engineering senior manager Kirk Moss.
He explains that the 11kV VSD complements WEG Automation Africa’s existing portfolio, “filling a gap in the 11000 V VSD sphere”.
WEG Automation Africa, a member of the Zest WEG Group, based the VSD’s design on cascaded H-bridge (CHB) topology, using multiple low voltage power cells in combination to achieve the desired voltage output. The input switch, phase-shifting transformer and VSD are fully integrated in a single medium voltage panel.
Moss says that the CHB topology has enabled WEG Automation Africa to achieve up to 13.8 kV in output voltage. He adds that the common voltages used for electric motors in Africa are 3.3 kV, 6.6 kV and 11 kV, and the new WEG 11 kV, “fits nicely to the complete range”.
Moss states that its introduction affords WEG Automation Africa even greater flexibility in its market offering, “further enhancing our capability to provide customised solutions”.
The VSD delivers high quality input power using low harmonic multi-pulse transformers. Users benefit from a high efficiency of over 96.5% throughout the entire load range, and a power factor of more than 0.95 throughout the entire speed range.
In standard configuration, the 11 kV VSD is available from 40 A to 400 A – or 640 kW to 6 500 kW – although larger sizes are available if required.
One of the options on the MVW3000 range is an automatic cell bypass solution, which ensures minimal reduction in the output-rated torque. Moss notes that redundant power cells can also be added to the design to ensure that 100% torque is maintained.
He notes that the new product line arose from the company’s commitment to continuous product development and improvement, adding that up to 3% of the company’s revenue is reinvested into research and development aimed at creating new products or enhancing existing ones.
The 11 kV VSD can be used in “any application”, from light-duty applications, such as fans and pumps, to heavy-duty applications including conveyors. However, “The WEG MVW3000 is particularly suited to applications where there are standard motors with no special insulation,” Moss says, “or where existing motors are being modified for VSD control”.
The 11 kV VSD’s multilevel output voltage makes it especially suited to retrofit applications, “although it can of course be used in greenfield applications where we’re installing the motor as well as the VSD”.
Two 11 kV units have already been used for 850 kW ventilation fan motors in an underground gold mine in Ghana.
He notes that WEG Automation Africa can assist original equipment manufacturers and consulting engineers with retrofit applications where potential energy savings exist. “For example, in an existing ventilation application that uses vane control to adjust the flow rate, it would be a big energy saver to replace vane control with a VSD, which adjusts the speed of the motor.”
Additionally, Moss comments that WEG Automation Africa, in terms of supplying drives has cut its teeth on multiple challenging applications, such as master-follower conveyor belt systems and synchronised bypass mill systems, adding that WEG VSD’s versatility offers a significant competitive advantage.
The existing WEG MVW01 range, based on the NPC (Neutral Point Clamped) topology, available in 3.3 kV and 6.6 kV versions, is supplemented by the WEG MVW3000 range which is available in 3.3 kV, 6.6 kV and 11 kV versions.
WEG Automation Africa can assist in providing the best choice of range, dependent on specific case.
WEG Automation Africa, as part of their commitment to investing in local manufacture, operates two manufacturing facilities in Gauteng. The Robertsham facility focusses on electrical panels such as motor control centres (MCCs).
The facility in Heidelberg extends the capability to large fabrication projects such as E-house substations.
WEG Automation Africa adopts a vertically integrated approach as far as possible, keeping all stages of the manufacturing process in-house. This allows control of the quality process.
Moss comments that WEG Automation Africa is committed to increasing local manufacture.
To that end, WEG Automation Africa has added new products to its local manufacturing capability, including a fully withdrawable MCC, fully arc resistant MCC and low voltage modular VSD panels.