Engineers from Moscow's NIU MEI have developed a power inverter for electric and hybrid aircraft that allows power electronics to be installed remotely from the electric motor. Such a solution can be useful, for example, when the motor is in the nacelle and the inverter is in another compartment of a drone or air taxi.
The main problem arises due to the long cable and fast SiC transistors: when switching, they create significant overvoltages at the terminals of the electric motor. NIU MEI designers proposed using a three-level circuit instead of a two-level one.
As a result, according to mathematical modeling, the overvoltage amplitude decreased by more than half. With a DC link voltage of 540 V and a 2 m long cable, the indicator decreased from 560 to 250 V.
At the same time, the developers did not add an external dU/dt filter. The design includes three three-level SiC modules, a separate IGBT module for voltage balancing, and three current sensors.
Even if one current sensor fails, the system can continue to operate by calculating the current of the corresponding phase mathematically. The main power supply for the electronics is also supplemented by a backup source.
The declared inverter power reaches 40 kW, and for 5 minutes it can operate with a load of up to 60 kW.