IEEE TRANSACTIONS ON MAGNETICS, VOL. 49, NO. 4, APRIL 2013 1367 Amorphous Soft Magnetic Materials for the Stator of a Novel High-Speed PMBLDC Motor Roman Kolano , Krzysztof Krykowski , Aleksandra Kolano-Burian , Marcin Polak , Jan Szynowski , and Przemyslaw Zackiewicz Institute of Non-Ferrous Metals, Gliwice 44-100, Poland Faculty of Electrical Engineering, Silesian University of Technology, Gliwice 44-100, Poland This paper presents results of a research work related to the development of the production technology of the amorphous cores de- signed for application in permanent magnet brushless direct current (PMBLDC) motors. The cores were made from the Metglas 2605 SA1 amorphous ribbon, from which rings of the specific external and internal diameters were cut using a laser technique. Next, the rings were stacked up so as to form a core of a required height, subjected later to the consolidation by pressing, followed by an appropriate heat treatment. Finally, the cores were coated with an epoxy resin to protect them against delamination and used as stators in a prototype high-speed electric motor, 1 kW in rated power and 70 000 rpm in a rotary speed. The motor incorporating these amorphous cores was subjected to the performance tests, which confirmed their proper operation and satisfactory mechanical characteristics and efficiency. It was found that power losses in the stators from the amorphous material were considerably smaller than those in the conventional stators from the silicon steel, and they did not exceed 7 W. Therefore, an application of the amorphous soft magnetic materials in the high-speed PMBLDC motors may contribute to eliminating the need of using additional cooling systems in these motors. Index Terms—Amorphous materials, high-speed electric motors, stators. I. INTRODUCTION T HE amorphous soft magnetic materials (ASMMs) have found many practical applications in power electronics, particularly in various transducers, sensors, distribution trans- formers, and so on, contributing to considerable electric en- ergy savings. In case of distribution transformers, replacement of the conventional cores from electrical steel with the amor- phous cores resulted in the reduction of no-load losses even by 70% [1], [2]. Similarly, our preliminary studies [3] showed that application of the ASMMs in the stators of the electric motors, particularly high-speed motors with a rotary speed exceeding 30 000 rpm, enables considerable reduction of the power losses in a stator. Because of great demand for high-speed motors de- signed for application in many areas of modern industry and technology, it can be expected that widespread implementation of the amorphous materials in these motors might bring consid- erable electric energy savings [4]. However, to replace electrical steel with an ASMM in the high-speed electrical motor, it is nec- essary to develop new designs of the stators and the technolo- gies for their forming. Great difficulties are encountered during forming the stators from these novel materials, mainly because of the brittleness of the amorphous ribbons and their relatively small thickness reaching typically about 25 microns. The studies on application of the amorphous soft magnetic materials for the stators of the electric motors have been un- dertaken relatively recently [5]–[7]. They referred mainly to the motors operating with a rotary speed of an order of 3000 rpm, where replacement of a stator from the FeSi electrical steel with the stator made from an amorphous material resulted in Manuscript received August 20, 2012; revised November 12, 2012; accepted December 11, 2012. Date of publication December 20, 2012; date of current ver- sion March 20, 2013. Corresponding author: R. Kolano (e-mail: romank@imn. gliwice.pl). Digital Object Identifier 10.1109/TMAG.2012.2234757 a decrease of power losses by about three times. The aim of this work was to develop production technology of the amor- phous cores designed for application in the stators of the perma- nent magnet brushless direct current (PMBLDC) motors. The technology for heat treatment of the Fe Si B alloy has also been optimized to make it suitable for application in the sta- tors of PMBLDC motors. The technology for the production of ring-shaped cores to be used in the stators has been developed. The consolidated ring-shaped cores were used in the stators of the prototype high-speed PMBLDC motor, 1 kW in rated power and about 70 000 rpm in rated speed, which was subjected to the performance tests. II. SELECTION OF THE AMORPHOUS SOFT MAGNETIC MATERIAL FOR THE STATOR CORE The main types of power losses in the electric motors are copper losses (in winding resistance), the losses in mag- netic circuits (in iron) , and the mechanical losses . The total losses can be expressed by the following formula: Fe At the increase in a rotary speed (frequency), the mechan- ical and iron losses increase rapidly, which results in high total losses in a high-speed motor. The mechanical losses cannot be fully eliminated but can only be reduced to some extent. There- fore, it is necessary to ensure that the losses in magnetic cir- cuits be at least by one order of magnitude lower than a sum of copper and mechanical losses. The acceptable level of losses for the assumed construction of a motor and the cooling conditions related with this construction is of an order of 100 W, whereas the mechanical losses at the speed of about 70 000 rpm are of an order of 80 W [3]. Significant reduction in the iron losses can be obtained using low-loss special materials such as Fe-based amorphous soft magnetic materials. The main requirements in selecting a suitable soft mag- netic material for the stator of a high-speed motor are the lowest possible power losses at elevated frequencies (about 0018-9464/$31.00 © 2012 IEEE