High Purity Aluminum in Cryogenic Motors for Electric Aircraft

View Video Presentation: https://doi.org/10.2514/6.2023-4539.vid High purity Al (HPAL with residual resistance ratio | RRR of about 2000) can be considered as alternatives to superconductors for cryogenic AC applications e.g., in the stators of electric aircraft fan motors. Such conductors can be competitive with superconductors in certain frequency bands. But their low yield strength renders them difficult to manufacture and unsuitable for magnet applications. To increase yield strength, the pure Al can be reinforced by encasing it in a high strength alloy sheath, CuNi. In this effect, transport current applied to the composite is divided between the core and the sheath in the inverse ratio of their resistances; the core current is dominant and in the presence of the applied field, produces a Hall voltage which drives a current along the sheath and power proportional to I2/ρH where ρH is the Hall resistivity. In this work, a higher resistivity matrix Cu10Ni along with a Nb barrier was used to strengthen the composite and prohibit undesirable interdiffusion in to the Al core while working to restore high-conductive properties. A comparison of theoretical AC loss contributions of each viable conductors for electric aircraft applications are made for 20 K and frequencies up to 500 Hz. The RRRs of the HPAL/CuNi monofilamentary and multifilamentary composite conductors were shown to be 1135 and 923 respectively.