The project was aimed at an increase of power density (kW per kg) of a three-phase inverter for aerospace application (power range 10 … 50 kW) of at least 10% with a concomitant compliance with RTCA DO-160, chapter 21 CMC limits.

The increase in power density was achieved by implementing an innovative topology based upon:

• Transition of the H5 or HERIC topology from single phase to a three phase inverter implementation
• Application of the 3L-T-Type inverter which can be derived from a 2L-inverter with three additional, bidirectional switches which connect the AC terminals with the center-tapped DC link
• Applying of appropriate modulation techniques which make use of switching states with reduced CMV levels

The resulting solutions were compared with a state-of-the-art 2L-VSI power core based upon the following criteria:

• Produced CMV and CMC levels, given by a quality parameter based upon RTCA DO-160, chapter 21
• Total weight for a 10 kW and a 50 kW power core implementation taking into account all relevant parts incl. gate driver, passive components for filter and cooling. The 10 kW power will be air cooled (natural convection), the 50 kW power core liquid cooled
• Efficiency
• The influence of the switching speed dv/dt will be taken into account, as today there exists a limit of approximately 5 kV/µs for the motor. Furthermore a too high dv/dt produces a significant amount of EMI