Comparison of phase-leg circuits for cryogenic operation in the all-electric aircraft

Abstract

Commercial all-electric aircraft are projected to be flying as early as 2035, where hydrogen is selected to supply fuel and coolant. The cryogenic aircraft's powertrain includes the turbines, generators, power electronics and fan motors. As most of the powertrain is located at cryogenic temperature, it is preferable to co-locate the power electronics in the same region to reduce the engineering system's complexity. Silicon super-junction MOSFETs are known for their high efficiency, thus lower cooling requirements at cryogenic temperature. However, in phase-leg circuits, the behaviour of the MOSFET's intrinsic diode, and its output capacitance are challenging. These issues can be addressed by using the MOSFET with ancillary power devices to realise diode deactivation. This paper compares different permutations of intrinsic diode deactivation devices at room temperature and cryogenic temperature. The paper presents a demonstrator phase-leg built with different ancillary power devices. It is operated from a DC voltage of 270 V, and supplies a phase current of up to 10 A.

Protection System Architecture for All-Electric Aircraft

“…Table I shows the performance of semiconductor devices at cryogenic temperatures. The conduction losses can be determined by the on-resistance (RDS(on)) for MOSFETs [7]- [14] or the forward voltage (VForward) for IGBT [15]- [17], both of these values decrease for both Si MOSFET and Si IGBT devices and hence are better options to be used at cryogenic temperature. The switching energy (ESW) has been shown to decrease with the decrease of temperature for Si MOSFET and Si IGBT.…”

“…The architecture of all-electric aircraft is presented in Fig. 1 and based on previous literature [5]- [7], where the entire system is immersed inside the cryostat. From the figure, both the converter and protection systems are immersed inside the cold temperature, this is better from the engineering point of view to avoid complex transitions from cold to ambient temperatures and vice versa, thus reducing heat leakage.…”