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The present work deals with a method of modelling a traction system in PSpice with the consideration for optimal cable arrangements for reducing conducted electromagnetic interference. Multiconductor transmission line (MTL) theory is adopted to model the cable which connects the pulse-width modulation (PWM) source inverter and the motor. A simple decoupling transformation method is proposed and used to transform the MTL into several single transmission line, which can be easily modelled in PSpice. The PWM controlled voltage source and induction motor are also included in this model. Thus, the full model for a traction system is realised in PSpice. From system simulation, the voltage oscillation in the cable is observed and the conducted electromagnetic noise in the system is studied. The relationship between the frequency of the noise and the length of feeding cables are also demonstrated in this work. In order to mitigate the high-frequency noise, a cable system with a fourth parallel earth conductor is proposed and the noise level is indeed reduced by this technique. This modelling procedure for traction system can be used for any specific application like the electrified railway traction system.
Date of Publication: March 2012