In recent years, the global environment has faced more severe challenges, and it is imminent to improve motor efficiency and reduce motor loss. In addition, with the rise of new mobile technologies, the use environment and specification requirements of motors have also changed, requiring smaller motors with higher power output. In order to meet these requirements, increasing the rotation speed of the motor has become a solution, and even for small motors, the output power can be increased by increasing the rotation speed. However, as the speed increases, the iron loss of the motor core will also increase sharply, resulting in a decrease in efficiency.
The motor core is usually made of non-oriented electrical steel plate, and the standard plate thickness is 0.5 mm and 0.35 mm. This material is selected because the high-speed rotation of the motor is related to the high frequency of the magnetic field in the iron core, and the iron loss of the electrical steel plate will increase with the increase of frequency. This is mainly due to eddy current losses. Eddy’s recent loss can be expressed by the square of the frequency, magnetic flux density, and plate thickness.
In order to suppress the increase in iron loss caused by frequency, people have developed ultra-thin electrical steel sheets, which can greatly reduce the increase in eddy current loss relative to frequency while maintaining the high saturation magnetic flux density and other characteristics of non-oriented electrical steel sheets. It is reported that ultra-thin electrical steel sheets are manufactured by re-rolling existing non-oriented electrical steel sheets. The development of this ultra-thin electrical steel sheet is expected to play an effective role in fields such as small high-speed electric motors.
However, there are still difficulties in making wide-width ultra-thin electrical steel sheets, and how to effectively use ultra-thin electrical steel sheets to manufacture large-scale motor cores has become an issue. For this reason, people have developed an extremely thin electrical steel strip coil core called “wound laminated core”, which can achieve the goal of large-scale motor cores even if the width is narrow. This type of iron core has a plate thickness of only 0.08mm, which is very thin and can be made into a coiled shape. By increasing the number of windings, it can achieve a larger size relative to the radial direction.
In general, a “wound core” refers to a core produced by winding an existing electrical steel sheet, while a “wound laminated core” refers to a core produced by winding an ultra-thin electrical steel strip with a thin plate thickness. This type of core maintains interlayer insulation by winding an extremely thin electrical steel strip with an insulating coating.
At present, although a method of winding an iron core with a thinner amorphous material has been developed, the interlayer insulation performance of the iron core cannot be maintained because the amorphous material itself has no insulating coating. In contrast, wound laminated cores are wound using extremely thin electrical steel strips with insulating coatings, so that interlayer insulation can be maintained.
Researchers such as Wakabayashi Daisuke of the University of Arts and Sciences in Japan studied the changes caused by the core structure by comparing the structure of the wound laminated core and the traditional laminated core. At the same time, by evaluating wound laminated cores made of ultra-thin electrical steel strips of different thicknesses, the optimal thickness and manufacturing conditions for further reducing iron loss were explored.
They believe that the wound laminated core made of the newly developed ultra-thin electrical steel strip has magnetic properties comparable to conventional laminated cores. By increasing the number of windings, radial size can be achieved, which contributes to the reduction of loss and size of high-speed rotating electrical machines.
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