High speed AC locomotives: harmonic and interharmonic analysis at a vehicle test room

The paper presents and analyzes the results of harmonic and interharmonic measurements performed at the vehicle test room of CRIS Ansaldo on the new high-speed locomotive ETR500. The adjustable speed drives of this locomotive utilize PWM-controlled converters to both rectify the voltage of the AC supply system and feed AC motors. These converters show advanced control characteristics, energy efficiency and currents distorted in terms of harmonics and interharmonics of reduced amplitude but with a wide range of frequencies. Harmonics and interharmonics are evaluated in different operating conditions. In particular, significant conditions are obtained tuning realistic resonance frequencies by means of variable power capacitors, properly designed. General problems such as test room flexibility and ability to reproduce realistic railway system conditions are discussed.