Radio Disturbance Evaluation of Si- and GaN-Inverters

Abstract:
Inverters are widely used to drive electrical machines. Due to their switching operation, these devices inevitably generate EMC emissions. The demand for high efficiency leads to fast switching (high du/dt) inverters, which do not only emit conducted EMI but also radiated disturbances. Thus, this paper studies radiated emissions of different inverter configurations by using the easily applicable radio disturbance method instead of the cumbersome and time consuming measurements in a chamber. The study reveals that for conventional Si-inverters, shielding of the cables between inverter and motor as well as a metal case do not deliver a sufficient reduction of emissions below 100 MHz. Recently, GaN-devices are used in inverters. Due to their higher switching speed (higher du/dt) emissions may increase further, while their switching losses are reduced. In order to mitigate low frequency radiated emissions, a LC-filter is required. When applying proper shielding, low emissions at high frequencies can be achieved. The paper demonstrates that the radio disturbance measurement method can be an attractive alternative to the semi anechoic chamber during the development phase.