| In recent years considerable progress has been made in making power electronics (PE) such as frequency converters and switched mode power supplies more efficient by using IGBTs (insulate gate bipolair transistor) and switching them faster. Furthermore the voltage swing of IGBTs is higher compared to BJTs. The advantage of IGBTs is that the dissipation is decreased which has a beneficial effect on reliability. The adverse effect is an increased level of electromagnetic interference (EMI); the parasitic capacitance between the transistor and the environment (ground of cool fins) is the current path causing a high level of (mainly) common mode currents. The common mode impedance of the load determines the current amplitude. For instance, in mechatronic and drive applications the parasitic capacitance between the motor windings and the housing closes a common mode loop. The common mode current path cannot be reduced by using feed through capacitances because this will increase the current in the loop formed with the transistor, causing overheating of the transistor. Thus inductors have to be applied, but these are saturated due to the high level of common mode current. Ferrite inductors become bulky due to the low saturation flux density and the frequency range limited when using steel lamination inductors. The benchmark is that 2 times the volume of the active components is needed for the passive component, and this ratio is still increasing when transistors are switching faster (to reduce heat dissipation within the transistor). Furthermore conventional off-the shelf small and low-parasitic (feed through) capacitors are not available for the large voltage range as applied with IGBTs, especially not for the (ungrounded IT mains supply). Using an approach in which functional, thermal and electromagnetic effects are taken into account simultaneously, new techniques to solve EMC problems in industrial power conversion systems will be researched and developed. The power electronic functional aspects and the EMC noise aspects will be combined in an integral design approach. Objectives regarding the performance are: - reduction in EMI potential - reduction in volume - reduction in weight while the functional performance and thermal performance remains equal. In order to achieve the above objectives we will investigate new concepts and innovative techniques. In addition the methods used will be translated into useable design rules for industrial applications, focused on EMI. This will enable industry to design power electronics faster and with lower risk. |
