Trafo Power Solutions says four of its dry-type transformers have been proving their worth on a mobile process plant at a Sierra Leone mine since last year.The dry-type transformers have been so successful in powering the process plant that the customer has ordered six more for its recent phase two upgrade.Trafo Power Solutions Managing Director, David Claassen, said: “The mine required a solution that would withstand the demanding conditions of a mobile process plant needing to be moved frequently over rugged mining terrain – as often as once a month. They could not risk using a conventional oil-cooled transformer as they needed to avoid any risk of fire or oil leaks. They also needed a product that would require little to no maintenance.”The second contract was a repeat of the initial order and comprises two 800 kVA units, one 1,600 kVA unit and one 2,000 kVA unit as well as a further two transformers – 1,600 kVA and 800 kVA – which will replace two existing oil filled transformers.The company said: “Demonstrating its flexibility in meeting specific customer requirements, Trafo Power Solutions designed the solution to cater for the mine’s unusual voltage levels of 13.2 kV/480 V at 60 Hz.”The transformers are installed in a 6-m-long E-house on the mobile process plant, which is moved around the site on skids as required by the mining plan.“We were able to customise the design of the transformers for the customer’s specific application,” Claassen said.“This required a special reinforced frame to accommodate the constant vibration of the working plant, as well as the bumping motion when the skid-mounted plant is dragged to a new location. The design also included anti-vibration damping on the transformer feet, to further mitigate the impact of the vibration.”The entry of Trafo Power Solutions dry-type transformers to the African market coincides with a growth in the use of modularised sub-stations, according to the company. “Due to the absence of oil as a coolant in dry-type transformers, they are suitable to be used in confined spaces without any of the conventional infrastructure usually necessary to protect the environment from possible oil spillage,” Trafo said.Claassen said: “Modular and mobile sub-stations are growing in popularity for applications all around Africa, as they can be fully prepared under workshop conditions, reducing the work required on site.“In terms of the installation of the transformer, for instance, we ensure that the temperature control relays are fully programmed and tested in South Africa, along with the fan system – making it ready for action on site.”In the unlikely event of any further attention being necessary, Trafo Power Solutions can mobilise service support to any of the sites it supplies, it said.