Research On Track Current Suppression Scheme Of SDA1 Diesel Locomotive

SDA1 diesel locomotive(after this referred to as locomotive)is an AC transmission trunk freight locomotive developed for the Australian standard gauge railway.The locomotive met the requirements of Australian and UIC standards.It performs well in a complex environment with high temperatures,dust,and rainstorms in Australia,reaching a world-class level.However,during the early operation period,the DPU malfunction of the track signal monitoring device occurred,which affected the reliable operation of the Australian standard gauge railway.According to many previous analyses,the root cause of this problem lay in the excessive track current in the 1600Hz-2700 Hz "Audio" section during locomotive operation.Based on this,this paper analyzes the generation mechanism of track current according to theoretical analysis.Combined with many field measurements,the characteristics of track current are analyzed,and the key influencing factors are discussed.On this basis,a comprehensive suppression scheme of locomotive track current is designed to meet Australia’s electromagnetic and signal compatibility access test requirements.The main research contents include the following three aspects:(1)Combined with the central electrical wiring diagram of the locomotive,this paper introduces the operation mechanism of the locomotive,the working principle of the traction inverter,and the electromagnetic characteristics of the asynchronous traction motor.Then,it analyzes the internal current flow direction of the locomotive integrated grounding system.Moreover,the generation mechanism is studied.And the primary sources of the locomotive track current are discussed,including common-mode voltage,electromagnetic field coupling induced voltage,and axle induced voltage.The common-mode voltage has the most significant impact on the track current.(2)Using JT1·JS·IIG coil,gapless waveform power quality recorder,and magnetic field tester,the locomotive track current test scheme is formulated,and the locomotive is tested under different operating conditions(traction variation range [18～587] k N.The handle gear covers gears 1-8.The operating speed includes low speed(<13km/h)and high speed(>13km/h).The operating conditions include traction and braking condition.Meanwhile,the track current,interrail potential,and magnetic field strength are measured and recorded.Based on the field measured data,the characteristics of the locomotive track current are analyzed.The test results show that the track-current in the 1600Hz-2700 Hz "Audio" section has an amplitude of more than 30 m A near 1600 Hz and 1800 Hz,respectively,which does not meet the requirements of the Australian electromagnetic and signal compatibility access test.Furthermore,it conducts comparative analyses and finds that the track current and magnetic field intensity are positively correlated with the input quantity of the motor and the output of the locomotive,but not with the operating condition and gear of the locomotive.Therefore,it can be concluded that the most severe situation of track current is to provide test conditions for the suppression of track current of subsequent locomotives when all motors are input and the output of the locomotive is maximum.(3)Finally,a comprehensive optimal scheme for reducing the track current is proposed based on the generation mechanism and characteristics of the locomotive track current.These schemes include adding a shielding plate under the traction motor,adding a silicon steel sheet between the traction motor and the holding shaft to shield the magnetic field,optimizing the inverter control strategy,changing the frame control of the main drive system control method,applying dynamic braking control strategy to direct cast,and optimizing the grounding wiring.The field measurement results show that the track current after the comprehensive treatment scheme is adopted significantly reduced.Regardless of the locomotive running at low speed or high speed,locomotive traction or braking,the track current amplitude in the 1600-2700 Hz "audio" section is less than 30 m A,and the track current is effectively restrained.The correctness and feasibility of the proposed comprehensive treatment scheme are demonstrated.Finally,it summarized all the works of this paper and the future research direction has prospected.