Fixed-voltage thyristor convertor rolling-stock transformers to control DC traction motors

The more recent use of power thyristors on AC railway vehicles, with their facility for controlling the DC output, has simplified the traction transformer in that it need only be of a constant ratio. However, the demands of the thyristor circuit designer can still impose some transformer design problems, particularly when a variety of different output windings are required. The mechanical arrangement of modern traction transformers demands more compact integral units, with the transformer and its accessories contained in as small an envelope as possible. As a result of experience gained both from type tests on new designs of traction transformer, as well as operating experience on older designs, it is possible to achieve greater compactness, still using conventional transformer materials