Proterial, Ltd. (formerly Hitachi Metals) has developed a laminated bonded amorphous alloy ribbon for motor cores. Amorphous alloys—metals that do not have a crystallone structure due to being formed by cooling molten alloy rapidly—are a low-loss material and are considered to be suitable for high-efficiency motors.

However, because of their greater hardness and thinner material compared to electromagnetic steel sheets, their application in the mass production of motor cores has been limited to those for axial-gap motors—i.e., a motor with a stator sandwiched between two disk-shaped rotors. The newly developed laminated bonded amorphous alloy ribbon has a thickness close to that of electromagnetic steel sheets, enabling its application to radial-gap motors—a motor with a stator surrounding a cylindrical rotor.mdwhich are a type of motor commonly used as xEV drive motors.

Proterial said that it will continue to provide solutions to the thinness issue through lamination and at the same time provide solutions to punching—a machining process where material is placed between a die and plate, and the die is pressed against the material to punch out an arbitrary shape—through the optimization of die materials to help further expand the range of motors that use amorphous alloys.

Background. xEV drive motors, as well as motors used in industrial machinery, home appliances, and other applications account for roughly 60% of Japan’s electricity consumption. As such, there is a need for motors with greater efficiency. Since the reduction of iron loss of the core (iron core) is essential for greater motor efficiency, efforts have been ongoing to improve non-oriented electromagnetic steel sheet materials. These efforts, however, are said to be approaching their limits.

Amorphous alloys have recently been attracting attention as a low iron loss material that exceeds the limitations of electromagnetic steel sheets. It is known that iron loss can be significantly reduced by using amorphous alloys for motor cores compared to using ordinary electromagnetic steel sheets. However, amorphous alloys are about five times harder than electromagnetic steel sheets, resulting in a shorter service life of the punch die.

Additionally, the material is only about 1/10^th the thickness of electromagnetic steel sheets, resulting in lower productivity in the punching process. Due to these issues, their application in mass produced motors has been limited to axial-gap motors that avoid the use of punching processes.

Proterial, a leading manufacturer of amorphous alloys for transformer cores, has been engaged in ongoing research and development, building on its accumulated knowledge of amorphous alloys, to realize the application of cores made of amorphous alloys for radial-gap motors.

Proterial developed a technology for continuously laminating and bonding multiple sheets of amorphous alloy ribbons for radial-gap motor cores. The key points of this technology are selection of the adhesive and control of adhesive layer thickness. With the development of proprietary technology that enables formation of layers of adhesive thinly and uniformly, it is are able to achieve a high space factor of 90% or more and laminate the material, with no degradation in the excellent magnetic properties of amorphous alloys.

The laminated and bonded material has a thickness comparable to that of electromagnetic steel sheets, which improves material handling and significantly reduces the number of processing required.

Another feature is that with this increased thickness, the machining accuracy of the punch die can be relaxed.

Proterial has begun offering samples of bonded amorphous alloy ribbon to motor manufacturers and core fabricators.