New alloy from Vacuumschmelze GmbH yields 98% motor efficiency



Vacuumschmelze GmbH has announced advanced materials designed to maximise electric motor efficiency: The Ultravac 44 V6 alloy, with properties that significantly boosts performance optimisation in high-efficiency electric motors. The highest-profile application of this currently is the new HB-SIB aircraft from the Solar Impulse project, the motor of which uses ULTRAVAC 44 V6 in its stator and rotor assembly. The magnetic drive of the motor contains magnetic systems comprising small bonded segments of VACODYM rare earth permanent magnets. This design minimises eddy current losses in the rotor resulting in an exceptional motor efficiency of 98%. Nickel-iron (NiFe) materials are well-known alternatives to electrical steel, with lower saturation induction compared to electrical steel, enabling optimisation of rotor and stator assembly dimensions. Adding molybdenum to the alloy, Vacuumschmelze has succeeded in developing a new material tailored to the requirements of high-efficiency electric motors, offering very low iron losses. At 3.5 A/m, the coercivity of ULTRAVAC 44 V6 is approximately one-quarter that of electrical steel, resulting in reduced hysteresis losses. Its saturation magnetisation is lower, and at low field strengths its static initial magnetisation curve rises faster than that of electrical steel. Both cases deliver a flux density of 1 T at a magnetic field strength of 100 A/m. Important considerations for high-speed motors or motors with high pole numbers are not only hysteresis losses, but also eddy current losses, generated at high operating frequencies. Whilst these losses can be effectively controlled by reducing the lamination thickness, processing the ultra-thin metal sheets is a complex and expensive procedure. The use of ULTRAVAC 44 V6 enables eddy current losses to be significantly reduced thanks to the extremely high specific electrical resistance of the material - around 50% higher than that of electrical steel at 0.8 mWm. The new alloy properties allows extremely low iron lossesat a flux density of 1 T, and offers an iron loss reduction of between 70% and 80% compared to NO20 electrical steel for tape thickness of 0.2 mm.