July 23, 2017

Shaw Controls delivers containerised solution to drive mill

Shaw Controls, a Zest WEG Group company, reports the successful completion of its contract to supply a containerised electrical solution to a gold mine in West Africa.

Kirk Moss, medium voltage manager at Shaw Controls, says the containerised solution will supply power to drive a mill on this new mine.

“Containerised electrical solutions are becoming increasingly popular as these allow for speed of installation and are a particularly cost effective option for mine and plants operating in Africa,” Moss says.

The custom engineered sub-station comprises a medium voltage (MV) WEG Variable Speed Drive (VSD) and a dry type phase shift transformer driving a 2 000 kW, 6 pole, 6,6 kV squirrel cage WEG electric motor. The VSD is housed in the container while the oil cooled transformer is housed outside of it to facilitate heat dissipation.

Moss says that Shaw Controls has an established reputation for engineering and manufacturing quality bespoke containerised solutions at its Johannesburg facility. The extensive facility of over

12 000 m2 is manned by a team of skilled technical personnel and having the whole construction take place in one facility makes it easier for customers to do all quality and functional checks in one place. This solution underwent testing at Shaw Controls prior to being dispatched to site.

“What is particularly interesting about the solution provided is that it has been specifically engineered for this particular application and utilises specialised software for frozen charge protection,” Moss says.

The software, which interfaces with the VSD, allows the objective detection of a frozen charge condition by making use of torque measurements already being monitored by the VSD.

“With the addition of an encoder fitted to the electric motor, we are now able to monitor mill angle. And with the torque and angle measurements it is possible to detect if cascading has occurred within the mill,” he explains.

Another innovative feature of this solution is the supply of a Human Machine Interface (HMI) in the form of an interactive touch screen which has been configured to allow different levels of access. This has been done in a user friendly manner to ensure ease of use and also allow simple access to relevant data.

Moss says that the ability to extract the most relevant data and provide this in an intuitive and simplified format allows both operational and service personnel to monitor the requisite parameters.

This project made use of a WEG MVW01 VSD with 6,6 kV output. The input solution makes use of a 36 pulse rectifier and corresponding phase shift transformer. Moss explains that this combination was selected as the best option to minimise harmonics.

The WEG MVW01 VSD range is available in 3.3 kV and 6.6 kV versions. This is a neutral point clamped (NPC) topology and makes use of 6,5 kV IGBTs. These VSDs are engineered with few components translating into high efficiencies and optimal reliability.

Also available is the WEG MVW3000 which is available in 3.3 kV and 6,6 kV, and more recently in an 11 kV version. This is a cascaded H-bridge (CHB) topology which makes use of low voltage IGBTs. This has low voltage power cells with built-in redundancy (optional) which allows a faulty power cell to be automatically bypassed with loss of performance.

Shaw Controls’ product line includes MV switchgear and LV withdrawable MCCs – locally manufactured products that are independently certified in accordance with the IEC 62271-200 and IEC 61439-1/2 standards. According to IEC specifications, LV covers applications up to 690 V, while the MV range is from 1 kV up to 52 kV. All products carry ISO 9001 accreditation from Bureau Veritas.

Being part of the Zest WEG Group also allows Shaw Controls access to the substantial technical database and engineering resources of parent company WEG Brazil.

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