Purpose -The purpose of this paper is to investigate application possibilities of soft magnetic composites (SMC) in the design of high speed permanent motors for home appliances. Design/methodology/approach -The design of high speed permanent magnet motor (HSPM) with core made of SMC has been proposed. The governing information about SMC has been presented. The possible advantages and disadvantages of applying magnetic powder materials in the design of electrical machines have been studied. To solve the partial differential equations describing magnetic vector distribution in considered HSPM, the edge element method (EEM) has been applied. The formulas of permanent magnet and winding descriptions, and electromagnetic torque calculations have been presented and studied. To verify accuracy of methodology and functionality of the elaborated software, a prototype of the considered motor has been built and the experimental setup for testing torque and electromotive force has been elaborated. The comparison between measured and simulated motor characteristics have been presented and discussed. Findings -Comparison between measured and simulated motor characteristics proves the model accuracy. The obtained results show that the designed HSPM motor has sinusoidal electromotive force waveforms, low cogging torque value and the sinusoidal torque versus rotor angle characteristics. Moreover, it has been indicated that the application of SMC materials can reduce power losses in the high speed motors. Originality/value -The paper describes the development of the numerical method and software for analysis of HSPM with core made of powder materials.

Powder metallurgy allows designers of electric motors to implement new magnetic circuit structures. A relatively new concept is the use of a magnet system consisting of various types of magnets on one rotor, for example sintered and bonded magnets. This concept has been applied to the design and manufacture of the four-pole rotor of a synchronous motor with 400 W power and a rotational speed of 1500 rpm. In this motor, the stator of an asynchronous motor type Sh 71-4B is applied. The application of the new construction of the rotor resulted in an increase in motor efficiency and power factor compared to an asynchronous motor with the same volume.

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.

The measurements of impulse magnetic fields using different methods were investigated. The main goal was the comparison of methods for measuring a strong magnetic fields. Method based on a Hall sensor was compared with the method using the measuring coil. In addition, the comparison of analog and numerical integration of the back electromotive force e(t) is presented. The paper shows waveforms of magnetic flux density and current recorded under investigation. The paper presents measurements of the magnetic induction up to 3 T. The main goal of investigations is development of precise methods and cheap devices for measurements of strong impulse magnetic fields. Streszczenie. W pracy przedstawiono pomiary impulsowych pól magnetycznych z wykorzystaniem różnych metod. Celem pracy było ich porównanie. Metoda bazująca na pomiarze za pomocą czujnika Halla została porównana z metodami bazującymi na pomiarze napięcia indukowanego w cewce pomiarowej. Dodatkowo, w pracy przedstawiano porównanie dwóch metod całkowania analogowego i cyfrowego siły elektromotorycznej e(t). W pracy przedstawiono przebiegi indukcji magnetycznej i prądu zarejestrowane w czasie badań. Pomiary indukcji magnetycznej prowadzono w zakresie do 3 T. Głównym celem badań jest opracowanie dokładnych metod i tanich urządzeń do pomiaru impulsowych pól magnetycznych. (Pomiary impulsowych pól magnetycznych).

Magnetization of large Nd-Fe-B sintered permanent magnets is still challenging. This type of permanent magnet is electrically conductive, so impulse magnetization causes a flow of eddy currents which prevent magnetization of the whole volume of the magnet. The paper deals with the impulse magnetization of sintered Nd-Fe-B permanent magnets and shows a method for the determination of suitable parameters for the supply system. The necessary magnetic field strength for magnetization of the magnet to saturation was determined. The optimal magnetizing fixture supply voltage for magnetization to saturation was determined from simulations in PSpice software, finite element analyses in Maxwell 15 and measurements. Measurements of magnetic induction on the surface of the Nd-Fe-B magnet are also presented to ensure that a magnet with 70 mm diameter and 20 mm in height is fully saturated.

The paper presents the physical properties of soft magnetic iron composites and Nd-Fe-B bonded permanent magnets measured at room temperature and at liquid nitrogen. The objective of research was a determination of influence of liquid nitrogen temperature on the magnetic properties, resistivity and mechanical properties of different powder magnetic materials. Research was carried out for three powder materials: soft magnetic, i.e. Somaloy 700, AncorLam and hard magnetic powder MQP-B used for production of bonded magnets. Composite specimens were prepared by compression moulding technology.

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