A Scott connection-based three-phase to five-phase power transformer

Multiphase machines have become serious contenders for safety-critical applications that require wide fault tolerant capabilities and higher system reliability. However, this adds more complexity to the adopted power converters. Alternatively, passive transformation is a viable solution to obtain an n-phase supply from the three-phase grid. This paper investigates the existing connections of passive transformation and proposes a transformation, based on the well-known Scott connection, to convert the three-phase grid voltages to an n-phase supply. In comparison with other connections in the literature, the proposed connection uses only two magnetic cores with less number of total coils, hence less total transformer volume. The paper also introduces the general per-phase equivalent circuit for three-phase to n-phase transformer, and the required modifications to conventional open-loop and short-circuit tests to estimate the transformer parameters. A prototype transformer is designed and built to investigate the proposed connection.