Hitachi Ltd and Hitachi Industrial Equipment Systems Co Ltd have developed a motor that uses cores made of amorphous metal coupled with ferrite magnet rotors. The motor does not require magnets made of rare earth metals such as Neodymium (Nd) or Dysprosium (Dy). The 150W prototype showed an efficiency of 86%—a 5% increase over Hitachi’s current 150W motors which do use expensive rare metal magnets.
|Hitachi’s amorphous metal prototype. Click to enlarge.|
Amorphous metal has a disordered atomic structure in contrast to the crystalline structure of conventional metals, and features a high tensile strength and extremely low magnetic losses. As such, it has been a target of interest for motor development for decades. A study by researchers at the Tokyo Institute of Technology published in IEEE Transactions on Industry Applications in 1989 (Fukao et al.), for example, found that a prototype super-high-speed reluctance motor built using amorphous metal for both rotor and stator cores reduced core losses by a factor of five (at 48,000 rpm) compared to a silicon-iron machine. The reduction in the core comprised 33% of total losses. The amorphous metal motor showed a six-point efficiency gain over the silicon iron machines, with 85% efficiency of 85% and a power factor of 0.46 at an output of 372 W.
A major problem with amorphous metal, however, has been the inability to manufacture it economically due to the difficulty in cutting and machining the material, which is harder than sheet steel. For the prototype, Hitachi and Hitachi Industrial Equipment Systems applied technologies developed for transformers that use amorphous metal to manufacture the iron cores.
Hitachi plans to commercialize the amorphous metal motors in three years for use in industrial equipment, and plans to increase output capability to up to the 10 kW class of motors to support a range of applications.
Fukao, T.; Chiba, A.; Matsui, M. (1989) Test results on a super-high-speed amorphous-iron reluctance motor Industry Applications, IEEE Transactions on Volume 25, Issue 1 Page(s):119 - 125 doi: 10.1109/28.18881