Study On The Electromagnetic Compatibility Of RS485 Bus In HXD3D Electric Locomotive

The internal and external electromagnetic environment of electric locomotive body are becoming worse, so the safety operation of the train face many challenges. Here is a typical electromagnetic interference phenomenon-RS485 bus information offline between train control monitoring system and the main converter, which is happened in HXD3D electric locomotive.According to the electromagnetic interference phenomenon, an idea of fault diagnosis is given combining with the working principle of RS485 bus and laboratory experiments. Then the interference and coupling paths are analyzed. The research shows that the pulse produced by rapidly action of IGBT is not interfered with the normal work of RS485 bus. What’s more, RS485 bus’s coupling voltage between two signal lines A and B is coupled by the high voltage cables and the return current by body,but 159.4mV is maximum coupling voltage which is lower than the threshold voltage.In this paper, based on tested data of the magnetic field in the car body of high-speed as well as motor and ordinary car, magnetic field distribution characteristics in car body are obtained. According to "Railway Applications Electromagnetic Compatibility" (GB/T 24338), the magnetic field test results analysis is given;Train window’s power frequency electromagnetic induction magnetic field model is established. Through the contrast analysis, the model is greatly consistent with the measured data.The results show that train window’s power frequency electromagnetic induction magnetic field model established is consistent with the measured data and there is a positive correlation between the power frequency magnetic field transmitted through vehicle windows and the traction current. The test comparison were conducted and with the error below±5%. According to "Power Frequency Magnetic Field Immunity Test" (GB/T17626.8), immunity of RS485 bus communication system is tested using immersion method and results show that the power frequency magnetic field inside the body can’t lead to information offline.In addition to, the spectrums of offline catenary arc are measured and simulated by Ansoft Maxwell14. Then RS485 bus on transmission reliability.. information offline produced by arc discharge is researched and analyzed. The results show that unbalance vehicle body voltage influenced by offline catenary arc discharge is the main cause for information offline.