Magnetic properties of Fe based composite materials with different particle sizes under a cryogenic condition have been investigated. Realisation of this venture has been carried out at the liquid nitrogen temperature. Results of energy loss density were obtained from measurements of the static (dc) hysteresis cycles ranging from 0·1 to 1·0 T. In turn, results of power loss density were obtained from measurements of the dynamic (ac) hysteresis cycles ranging from 50 to 1000 Hz and at the maximum flux density of 0·5, 0·8 and 1·0 T. The study confirmed the influence of temperature on magnetic parameters. It has been shown that total power loss density has increased with decreasing temperature. We report changes in a nature of energy loss after immersing specimens made of soft magnetic composites in liquid nitrogen. Measurements of the maximum relative permeability were also conducted.

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Application of permanent magnets bonded by rubber is still growing, especially in the automotive industry. Magnetic and mechanical properties of permanent rubber magnets can be tailored by a production's technology and a magnet's composition. Permanent magnets bonded by rubber are produced by a method called calendaring. Physical properties of rubber bonded permanent magnets depend on a type and amount of hard magnetic powder in a mixture with rubber. Anisotropic strontium ferrite powder and spherical isotropic Nd-Fe-B alloy powder were used in research. The results of measurements show that with an increasing amount of ferrite powder magnetic properties and Shore hardness increase whereas tensile strength decreases. Addition of Nd-Fe-B powder to the mixture instead of some ferrite slightly increases magnetic properties of magnets.

Φ Abstract -Powder magnetic circuits find more and more application in modern electric machines. These magnetic circuits frequently comprise soft magnetic core and powder permanent magnets as a source of magnetic flux of excitation. It is connected with a lot of advantages of these kinds of materials. The main purpose of the work is to design a brushless DC motor with powder permanent magnet and powder soft magnetic core. It was assumed that the powder magnetic core will be prepared from iron powder bonded by resin and permanent magnet will be prepared from powder of Nd-Fe-B melt-spun ribbon. Investigation of technology of magnetic materials was done and presented. Measurements of properties of magnetic materials were considered in design and analysis of motor. During designing process the dimensions and operational parameters of designing motor were assumed. Permanent magnet DC brushless motor with nominal power 250 W and rotational speed 6000 rpm was designed.