Electromagnetic simulation software is a key tool in the design optimisation of power transformers for Kolektor Etra, a Slovenia-based electrical equipment manufacturer. The Opera-3D software package from Cobham Technical Services is being used for a diverse range of design related tasks, from the detailed characterisation of design aspects such as eddy current losses by quantifying stray magnetic flux, to comparing the efficiencies of different construction and geometry ideas for transformers. In a recent analysis of magnetic shield placement in a three-phase power transformer, the company was able to reduce total eddy current losses by as much as 30 per cent, leading to a substantial reduction in transformer price and weight, and reduced long-term operating costs for the transformer operator.
Before investing in Opera-3D, Kolektor Etra used some free finite element software to perform tasks such as flux density and other electro-magnetic calculations. However, the lack of any 3D modelling capabilities meant that the company found it difficult to optimise their design in cases of unsymmetrical geometry, such as winding exits and core clamping structures. It therefore took the decision to move to a professional finite element package that offered 3D modelling.
Andrej Jurman, head of Kolektor Etra’s electrical design department, said: ‘Gaining a clear picture of the effect of design changes can provide significant cost-savings, which is why we regard the Opera electromagnetic field simulator as such a useful tool. Although the losses caused by stray fields are very hard to separate out from measured short circuit losses in a transformer accurately, modelling enables us to see the shape of stray flux and the places with the highest local loss generation visually.
'In this way we can evaluate and improve the efficiency of our designs and perform certain measurements. Because a large proportion of our transformer products are one-off designs, we do not model every transformer in detail – but our simulation results heavily influence our general design strategy, helping to maximise the efficiency of every product we make and providing us with a tool for continuous optimisation.’
