Measurement and Analysis of Radiated Electromagnetic Emissions from Rail-Transit Vehicles

Various operational considerations have led intro-introduction of solid-state dc propulsion control systems, to replace the older cam controllers in rapid-transit propulsion systems. The simultaneous introduction of audio-frequency signaling and train control systems using jointless rails has made it necessary to coordinate the design of these two new technologies in order to achieve intrasystem electromagnetic compatibility (EMC). At present, the conductive and inductive interference mechanisms are fairly well understood and this paper deals primarily with radiated electromagnetic interference (EMI) effects. Radiated emissions could potentially interfere with local radio-communications services or sensitive electronic equipment in the area. Measurement programs were conducted at various locations in the U.S. between 1979 and 1981. Magnetic (H) Field and Electric (E) Field measurements were performed over the frequency range 20 Hz to 1 GHz. Information from these measurement programs will provide a data base for eventual use in the preparation of recommended test procedures and emission limits for rail-transit systems. The use of a spectrum-analyzer system for the measurements of E-and H-Field levels emanating from a moving rail vehicle has many advantages. It was found that H-Field levels above 30 MHz decrease rapidly with distance and E-Field levels below 10 kHz were negligible.