A range of factors need to be considered when correctly sizing a transformer for optimal performance in any application, according to Ronaldo Bertoldi, engineering manager at WEG Transformers Africa (WTA).

Ranked among the largest manufacturers of transformers in South Africa – and serving a range of sectors including mining, industry and agriculture – WTA is a leader in distribution transformers, power transformers and mini substations.

“Sizing a transformer for a particular application can be done using a simple equation, but the selection process requires many other factors to be taken into account,” says Bertoldi. “Determining the right transformer for the job requires an in-depth assessment of the conditions under which the transformer will operate.”

He emphasises the difference between the full load current required by an application, and the start-up current if there is a direct online starting process. If the motor is initiated by a direct online start, this part of the operation could require a much higher current than when it is running.

Bertoldi also points out the significance of the distance between the source of the power and the equipment consuming the electricity, as will be a voltage drop that will affect the sizing of the transformer.

“Transmitting low voltage over long distances can also be more expensive due to the thicker cables required by the higher current,” he says. “Users can achieve a more cost effective solution in many cases by considering a step-up, step-down configuration, where the voltage is increased to facilitate longer distances, then reduced to the requirement of the equipment at its point of location.”

WTA’s years of expertise in manufacturing and repair equips it well to advise customers in the sizing and selection of the right transformer for their specific needs. Its Heidelberg facility is capable of locally manufacturing power transformers up to 40 MVA in voltages up to 132 kV as well as mini substations and ring main units. All distribution and power transformers are manufactured to SANS 780, BS 171 and IEC 60076 specifications under ISO:9001 quality standards.