EMI analysis in high power converters for traction application

The driving improvement in terms of IGBT switching losses reduction is accompanied by a significant increase of EMC noise problems. In this paper, the authors focused their attention on the electromagnetic noise radiated by the high voltage high power IGBT modules during the inductive turn-on. The noise variation and the dependence of each IGBT commutation phase is investigated by means of an experimental set-up that reproduces a real inverter used in railway applications. The EMC measures have been executed by means of an original experimental method that is most indicated for the high power inverter systems. The experimental and the simulation results demonstrate that the radiated electromagnetic noise is stimulated by the dv/dt voltage gradient and the amplitude of the noise is proportional to it. The main high frequency harmonic components of the emitted signal are stimulated by the voltage variations across the device during the first phase of the turn-on, whereas the signal is emitted by the freewheeling diode during the second phase of its reverse recovery when this diode is stimulated by a large voltage variation.