Innovative trains


Transforming transformers for lightweight traction


A prototype power-electronic traction transformer know as Pett has been developed by ABB and is currently being tested in an electric locomotive. The objective is to develop a compact, lightweight but powerful and energy-efficient converter for use on multiple-units where space and weight are at a premium.


I


T is often said that small is beautiful. But when it comes to technology, there are numerous


reasons why small is better. In many applications weight and space requirements directly influence productivity, and much research goes into footprint reduction. Some products, however, have largely resisted this tendency.


The minimum size of a power transformer is essentially determined


by the laws of physics, as the core must have certain dimensions to accommodate the magnetic field. Traction is a particularly challenging application for transformers, as the more space the transformer occupies, the less space is available for passengers. Its weight is also a factor in terms of permissible axleload and the additional energy needed to accelerate the train. To make this component smaller and


lighter, the laws of physics fortunately provide some scope for improvement in the form of frequency. The higher the frequency, the smaller the required core. But applying it to such large and heavy- duty items as traction transformers is about much more than scaling. To this end, ABB has developed a prototype power-electronic traction transformer (Pett) that is currently being tested in a locomotive.


In the early days of electric railways,


Pett is being tested in an SBB electric shunting locomotive at Geneva Cornavin station.


IRJ September 2012 69


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