Magnetic Properties Of Core Material Research Articles

Measurement and Modeling of Magnetic Materials under 3D Vectorial Magnetization for Electrical Machine Design and Analysis

The magnetic properties of magnetic cores are essential for the design of electrical machines, and consequently appropriate mathematical modeling is needed. Usually, the design and analysis of electrical machines consider only the one-dimensional (1D) magnetic properties of core materials, i.e., the relationship of magnetic flux density (B) versus magnetic field strength (H), and their associated power loss under 1D magnetization, in which the B and H are constrained in the same orientation. Some studies have also been performed with the two-dimensional (2D) magnetizations in which the B and H are vectorial, rotating on a plane, and they may not be in the same direction. It has been discovered that the 2D rotational property is very different from its 1D alternating counterpart. However, the magnetic fields in an electrical machine, in particular claw pole and transverse flux machines, are naturally three-dimensional (3D), and the B and H vectors are rotational and may not lie on the same plane. It can be expected that the 3D vectorial property might be different from its 2D or 1D counterpart, and hence it should be investigated for the interests of both academic research and engineering application. This paper targets at a general summary about the magnetic material characterization with 3D vectorial magnetization, and their application prospect in electrical machine design and analysis.

Performance and Design of an SRM with Amorphous Stator

The performance of the switched reluctance motor (SRM) greatly depends on magnetic properties of core material since it consists of only laminated-core and windings. This paper analyses the performance of an SRM with amorphous stator, which has very low iron losses. Copper loss, iron loss and efficiency of the SRM are estimated by finite element method. Furthermore, a suitable structure for the SRM with amorphous stator is examined on the optimization design.

Low temperature permeability and current noise of ferromagnetic pickup coils

For a non-destructive measurement of intensities of charged particle beams a Cryogenic Current Comparator is used which captures the azimuthal magnetic field of the beam by a superconducting pickup coil at 4.2K and transforms it into a current which is detected by a SQUID based current sensor. The current noise of the pickup coil and the bandwidth of this transformer depend on the frequency response curve of the complex permeability of the ferromagnetic core material embedded in the pickup coil. A measurement of the series inductance LS and series resistance RS of such a coil allows an indirect evaluation of the current noise contribution of the core using the Fluctuation–Dissipation-Theorem. These measurements were done with a commercial LCR-Meter in a frequency range from 20Hz to 2MHz. The current noise density was also directly measured using a SQUID-sensor. A comparison with between the direct and indirect measurement showed a good coincidence. Due to the critical temperature of the LTS-SQUID, noise measurements above 4.2K are not possible apart from using an anti-cryostat. The measurement of the series inductance LS and series resistance RS with an LCR-Meter works in the whole temperature range and provides a comfortable access to the magnetic properties of core materials. Compared to direct measurements, the indirect measurement thus allows a technologically simpler and broader determination of the core noise.

Development of a Switched Reluctance Motor made of Permendur

A switched reluctance (SR) motor consists of stator and rotor cores, and windings. Both the stator and rotor have salient poles. The stator has concentrated windings on each salient pole. On the other hand, the rotor has no windings and no permanent magnets. Therefore, the SR motor is a low cost, extremely robust, and wide-range variable-speed motor. The performance of the SR motor greatly depends on magnetic properties of core material since it consists of only iron cores and windings. This paper presents the development of a novel SR motor made of permendur which has extremely high saturation flux density and very low core loss. Two types of SR motors, one is made of conventional non-oriented Si steel, the other is made of permendur, are compared by simulation and experiment. It is demonstrated that the torque of the SR motor made of permendur is greater than that of the conventional Si steel by 20%.

Optimization of a Switched Reluctance Motor Made of Permendur

A switched reluctance (SR) motor has a doubly salient pole structure. A stator has concentrated windings on each pole, while a rotor is only made of iron core. Therefore, the SR motor is expected as a low cost, extremely robust, variable speed motor. The performance of the SR motor greatly depends on magnetic properties of core material since it consists of only laminated-core and windings. This paper investigates the performance of an SR motor made of permendur which has extremely high saturation flux density and very low core loss. Motor torque, iron loss, and efficiency of the SR motor are estimated by finite element method (FEM). Furthermore, a suitable structure for the SR motor made of permendur is examined based on the design of experiments.

Effect of magnetic properties of non-oriented electrical steel on torque characteristics of interior-permanent-magnet synchronous motor

The torque characteristics of interior-permanent-magnet synchronous motor (IPMSM), in which core materials were our conventional non-oriented electrical steel 35SX250 and our developed steels 35SXH, 27SXH with high permeability, were measured by a pulse wave modulation (PWM) inverter control. The torque characteristics of the motor with developed steels were superior to that of conventional steel. The advantage of developed steels was remarkable in the high-toque region. Experimental torque separation using current phase control showed that reluctance torque was strongly affected by the magnetic properties of core materials. And we did magnetic field analysis of the motors by finite element method (FEM). The flux density in the teeth of the stator core was higher in the high permeability steels than that in the conventional steel under the same current condition. The developed steels are expected to be suited to the stator material of IPMSM used as drive motors for electric vehicles and compressor motors for air conditioner.

Effects of Magnetic Properties of Core Material on Reluctance Motor Characteristics

The relations between reluctance motor characteristics and the magnetic properties of core materials are quantitatively investigated using equivalent circuit. High saturation magnetizations are required for core materials. Low iron loss materials are used as stator cores and SRM rotor core. High harmonic frequency is generated even in synchronous RM and then copper losses and iron losses increase. In IPM, reluctance forces are reduced by permanent magnet fluxes superposed in cores, but the force reduction is little in the case of IPM with ferite magnets. The magnetic anisotropic energies of core materials may increase reluctance force if the core materials are used near saturation magnetizations.

Equivalents Circuits for Motors, Representative of Magnetic Properties of Core Materials

The magnetic properties of core materials and the core conditions were represented in equivalent circuits for motors. In equivalent circuits for motor cores, real inductance L, imaginery inductance r/j and resistance R are connected in parallel to express the frequency dependences of iron losses. L, r, R are related respectively to permeability, hysteresis loss and eddy current loss. The magnetic properties of motor cores are affected by flux distribution, rotational flux, manufacturing stress and space harmonics and time harmonics in motors, and the figures 2, 4, 5 and 6 show the circuits which represent the effects. The equivalent circuits are composed of equivalent circuits for stator, rotor and air gap, and then this equivalent circuit analysis can indicate the most suitable core materials for each part. Using this equivalent circuit, the relationships between the characteristics of motors and the magnetic properties of core materials can be investigated in d. c. motor, synchronous motor, induction motor. reluctance motor (RM) and switched RM.

Spectrum of synchrotron radiation from an extended source

Induction sensors with cores in the shape of hollow cylinder are widely used because of such advantages as decrease of mass and simplicity of manufacturing cores with defined geometry. Replacement of a real tubular cylindrical core by the model in the shape of hollow ellipsoid of rotation with equal values of relative lengths, ferromagnetic volumes and fluxes, that is proposed in the article, allows to find the calculation algorithms for determination of electromagnetic parameters of cylindrical rod with solid and tubular cores. The obtained algorithms take into account the influence of both the geometry and magnetic properties of core material on the electromagnetic parameters and are suitable for engineering calculations.

Effects of ultrahigh temperature on magnetic properties of core materials

An experimental study has been made of the effects of temperature on the magnetic properties of the following ferromagnetic alloys: Orthonol, 4-79 Mo Permalloy, AEM 4750, L and Z Silectron, Transformer A, Audio Transformer A, 11.7 Alfenol, 15.5 Alfenol, 3 Mo Thermenol, 7-70 Perminvar, and Supermendur. Measurements were made of the d-c and 60 cps (cycles per second) magnetic properties in the temperature range of 24r-800 C (degrees centigrade). The materials were also evaluated after several temperature cycles between 24-500 C. The results indicate that, in general, high temperature decreased the maximum induction and the residual induction from their 24 C values. For all materials tested, with the exception of Supermendur and 11.7 Alfenol, the coercive force decreased with increase in temperature. The maximum permeability increased with increasing temperature until the Curie temperature was approached, then it started to decrease. The initial permeability also increased with increasing temperature, but unlike the maximum permeability, it generally started to decrease at a greater rate and at a lower temperature. Grain-oriented materials were more affected by temperature cycling than were unoriented materials. The effects of temperature cycling on the magnetic properties generally appeared as an increase in the coercive force, a decrease in the maximum permeability, a decrease in the residual flux density, and a decrease in the squareness ratio.

Effects of High Temperature on Magnetic Properties of Core Materials

An experimental study was made of the effects of temperature on the dc and 60 cps magnetic properties of the following alloys: Orthonol, 4-79 Mo Permalloy, AEM 4750, L- and Z-Silectron, Transformer A, Audio Transformer A, 11.7 Alfenol, 15.5 Alfenol, Thermenol, 7-70 Perminvar, and Supermendur. The results indicate that, in general, an increase in temperature decreases the coercive force and the maximum and residual inductions. Maximum and initial permeabilities increase with increasing temperature until the Curie temperature is approached, then they decrease. The initial permeability generally reaches a maximum at a lower temperature than does the maximum permeability.