Research of energy-saving composite materials for electric motors

. This article discusses samples of magnetic cores based on isolated powders of magnetic materials, and also investigates the main magnetic characteristics of magnetic cores using ASC100.29 iron powders.


Introduction
Recently, in various devices operating in alternating magnetic fields, cores made of composite powder materials with the necessary magnetic characteristics are widely used.At the same time, they have relatively small eddy current losses and high electrical resistivity [1,2,4].The required characteristics are achieved by doping soft magnetic materials based on iron with phosphorus or silicon with the introduction of special dielectric layers of organic and inorganic additives.This makes them competitive with conventional laminated electrical steel cores.The use of powder metallurgy methods in the formation of products of complex shape, in addition, makes it possible to obtain isotropic materials that change the nature of the magnetization, as well as the direction and distribution of the magnetic fluxAn analysis of literature data shows that the developed materials are subjected to heat treatment at temperatures below 800 °C [2,5].This is apparently due to the destruction of the material of the interlayers of thermosetting inorganic materials.To increase the magnetic permeability of the metal matrix, recrystallization annealing is best carried out at higher temperatures using high temperature resistant dielectrics.Most authors use glass-containing compositions, enamels, etc. as such materials.Such materials are in a liquid state at high temperatures, which contributes to the appearance of properties characteristic of these phases.The arising capillary forces can ensure the movement of liquid micro volumes, similarly to impregnation processes, into antiparticle voids [4,6].
Composite materials with the necessary set of performance characteristics are widely used in the nodes of various mechanisms.In any technical applications, certain properties of solids are used: electrical, magnetic, optical, thermal, mechanical, corrosion-resistant, etc.The production of magnetic materials with low energy losses during magnetization reversal is one of the urgent problems of industry today [1,5,8].Despite the fact that research and development of such materials have been carried out since the beginning of the last century, the study of the mechanism of magnetization reversal and improvement of the quality of these materials is still relevant today.This is due to the fact that magnetic materials are widely used in various electrical devices (generators, electric motors, measuring devices, inductors, etc.).

Experimental research
The technology for manufacturing experimental samples of magnetic cores based on isolated powders of magnetic materials is a multi-stage process [5,8].
For research, samples were made using ASC100.29 iron powder with particle sizes d > 0.1 mm and d < 0.1 mm and with an average insulation thickness based on phosphorus oxide ~ 1 nm, as well as samples based on ASC100.29 (d < 0.05mm) with insulating layer thicknesses of 10, 20, 30 nm.
Measurements of the magnetic properties of samples of experimental components for the stator and rotor were carried out on an express magnetometer (Figure 1), where losses and other magnetic parameters were determined from the magnetization reversal curves of the samples [6,7].
Measurement of the magnetic characteristics of magnetic circuits in a wide range of magnetic fields, demagnetizations frequencies and temperatures was carried out using an express magnetometer developed and manufactured at the Center [2,5].To normalize the magnetometer, the magnetic characteristics were first measured on a certified flux meter.An F5050 microwebermeter was also used to normalize the magnetometer.Figure 1 shows the main blocks of the express magnetometer, created in the laboratory of the physics of magnetic materials of the State Scientific and Practical Center of the National Academy of Sciences of Belarus for Materials Science, and Figure 2 shows the results of data processing in the express fluxmeter and magnetometer mode.
Studies of the main magnetic characteristics of magnetic cores using ASC100.29 iron powders (China, Hoganas) were compared with similar parameters for E320 electrical steel.For this purpose, cores 24 × 13 × 10 mm were made from strip steel and composite magnetic materials with a density of ρ = 7.6 g/cm3.Their static and dynamic magnetic characteristics have been studied, and the value of hysteresis losses has been determined [2,4,7].Samples of magnetic cores made of composite magnetic material were annealed in vacuum at a temperature of 400°C for 3 hours.The static characteristics were studied using an F5050 microwebermeter, and the dynamic characteristics and losses were studied with a flux meter and an express magnetometer in the frequency range up to 10 kHz and magnetic fields up to 30 kA/m.The field dependences of magnetization and losses at a frequency of 1 kHz for a low-frequency sample of a magnetic circuit based on ASC100.29 powder upon annealing in a vacuum of 350°C for three hours are shown in Figure 3 [3,6].It follows from the figure that a linear dependence is preserved in the change in magnetic induction and the magnitude of losses.

Research results
The study of losses during magnetization reversal of samples of magnetic circuits showed that hysteresis losses are 25-30% higher for samples based on powders sprayed with air compared to losses for magnetic circuits based on powders sprayed with water (Figure 4) [7,9].On the whole, comparative studies have shown a certain advantage in the value of magnetization reversal losses of purer iron powders obtained by the water spray method in comparison with powders sprayed with air [3,5,8].The main parameter that determines the possibility of using products in electrical devices is the magnitude of electromagnetic losses at different frequencies [5,[8][9][10][11][12][13][14][15][16][17][18][19][20].The results of preliminary studies of losses from the magnitude of induction are shown in Figure 5.In general, such studies have shown an advantage in the magnitude of losses for magnetization reversal of components made on the basis of composite materials compared to sheet electrical steel.

Conclusion
Thus, the conducted studies have shown an advantage in the value of losses for the remagnetization of components made on the basis of composite materials, compared with sheet electrical steel.In general, comparative studies have shown some advantage in the magnitude of remagnetization losses of purer iron powders obtained by the water spray method in comparison with powders sprayed with air.

Fig. 2 .
Fig. 2. Results of data processing in the express flux meter mode (a) and in the express magnetometer mode

Fig. 4 .Fig. 5 .
Fig. 4. Dependence of losses on the value of induction for a low-frequency composite material based on ASC100.29 during magnetization reversal in a full cycle -1 and in a quotient from the zero point -2 at a frequency of 1 kHz

Table 1
Fig 1. Appearance of the magnetometer