ABB has rethought the design of three-phase transformers and come up with a triangular shape that, it says, cuts no-load losses by about 20%, reduces the weight by 15–20% and the footprint by 25%, and can halve inrush currents.

Traditionally, three-phase power transformers have had a linear design with the three phases arranged side-by-side in two rows. But, says ABB, this destroys the system symmetry, and means that the transformer materials are not fully utilised. Its new TriDry transformer (above) has a triangular footprint that re-establishes the symmetry, saves weight and space, and is more efficient.

Each of the core’s three legs is linked directly to the other two. The result is a shorter, symmetrical path of magnetic flux in the core. The new design also opens up an extra path: as well as the usual rectangular path via the leg of the core and yoke, there is now a path via the triangular yoke.

The triangular footprint makes the maintenance-free transformer much shorter, while increasing its height only slightly. The smaller, lighter designs will offer more mounting options, ABB suggests.

Noise levels are said to be 5–10dB(A) lower than conventional transformers, while the extra magnetic return path via the yoke cuts inrush currents by 30–50% and reduces harmonics. The symmetrical design also cuts stray magnetic fields.