Improving the efficiency of electric motors has become a subject of interest amid growing concern about energy efficiency throughout the world. There have been ongoing improvements in the efficiency of industrial motors prompted by national regulations, with international standards having been formulated to define levels of efficiency. Hitachi has developed axial-gap electric motors that comply with the IE5, the most stringent of these efficiency classes, by utilizing amorphous alloys and drawing on Hitachi’s own design and manufacturing technologies. By developing techniques for reducing losses relative to motors in the IE4 efficiency class that involved assessing the motor’s internal magnetic characteristics and performing precise analysis and design, Hitachi came up with a motor design that significantly reduces the losses in the amorphous core and succeeded in achieving the IE5 efficiency class.
Fig.1. Comparison of electromagnetic steel and amorphous.
2.Contents of technology
(1) Decreasing core loss using “laminated core structure”
A “laminated core structure” which uses low-loss material such as iron-based amorphous metal with loss characteristics, approx. 1/10 that of magnetic sheet material used in conventional motors in the stator core of the motor, and the production technology for the new core structure were developed. As a result, deterioration due to processing which occurs in low-loss material such as iron-based amorphous metals was improved, making it relatively easier to manufacture a low-loss core. (Fig.2.)
Fig.2. Production method and structure of amorphous laminated core
(2) Increasing the capacity of double-rotor axial gap motors
In order to employ the double rotor axial gap motor which allows a greater amount of ferrite magnet to be used and thus dramatically increase the magnetic energy of the magnet, highly resilient stator and rotor structures which could endure a large torque and centrifugal force were developed. As a result, increased efficiency was achieved in energy-consuming medium capacity motors used in industrial applications as well as realizing the development of a motor without rare-metal magnets. (Fig.3.)
Fig.3. Thin Axial Gap Structure.
(3) Design technology of amorphous motor integrated oil free scroll compressor.
We developed an amorphous motor integral type of oil free scroll compressor which mounted the compression mechanism part and the motor part integrally and reduced the volume by 63%.(Fig.5.)
Fig.4. Efficiency of developed motor.
Fig.5. Amorphous motor integrated oil free scroll compressor.
*1 Member，Hitachi Industrial Equipment Systems Co.,Ltd. R&D Center ( AKS Bldg., 3, Kanda Neribei-cho Chiyoda-ku, Tokyo, 101-0022, Japan.)
*2 Center for Technology Innovation – controls, Hitachi, Ltd. (7-1-1, Omika-cho, Hitachi-shi, Ibarakiken, 319-1292, Japan.)
*3 Hitachi Industrial Equipment Systems Co.,Ltd. Air Compressor SystemsDivision (390, Muramatsu, Shizuoka-shi,424-0926, Japan.）
*4 Hitachi Industrial Equipment Systems Co.,Ltd. Air Compressor SystemsDivision（1116, Kozono, Ayase-shi, Kanagawa 252-1121, Japan.）
*5 Hitachi Industrial Equipment Systems Co.,Ltd. Drive System Division (7-1-1, Higashinarashino, Narashino-shi, Chiba, 275-8611, Japan.）