Core Power Loss Research Articles

Influence of Nb and Mo Substitution on the Structure and Magnetic Properties of a Rapidly Quenched Fe79.4Co5Cu0.6B15 Alloy.

The importance of amorphous and nanocrystalline Fe-based soft magnetic materials is increasing annually. Thus, characterisation of the chemical compositions, alloying additives, and crystal structures is significant for obtaining the appropriate functional properties. The purpose of this work is to present comparative studies on the influence of Nb (1, 2, 3 at.%) and Mo (1, 2, 3 at.%) in Fe substitution on the thermal stability, crystal structure, and magnetic properties of a rapidly quenched Fe79.4Co5Cu0.6B15 alloy. Additional heat treatments in a vacuum (260-640 °C) were performed for all samples based on the crystallisation kinetics. Substantial improvement in thermal stability was achieved with increasing Nb substitution, while this effect was less noticeable for Mo-containing alloys. The heat treatment optimisation process showed that the least lossy states (with a minimum value of coercivity below 10 A/m and high saturation induction up to 1.7 T) were the intermediate state of the relaxed amorphous state and the nanocomposite state of nanocrystals immersed in the amorphous matrix obtained by annealing in the temperature range of 340-360 °C for 20 min. Only for the alloy with the highest thermal stability (Nb = 3%), the α-Fe(Co) nanograin grows, without the co-participation of the hard magnetic Fe3B, in a relatively wide range of annealing temperatures up to 460 °C, where the second local minimum in coercivity and core power losses exists. For the remaining annealed alloys, due to lower thermal stability than the Nb = 3% alloy, the Fe3B phase starts to crystallise at lower annealing temperatures, making an essential contribution to magneto-crystalline anisotropy, thus the substantial increase in coercivity and induction saturation. The air-annealing process tested on the studied alloys for optimal annealing conditions has potential use for this type of material. Additionally, optimally annealed Mo-containing alloys are less lossy materials than Nb-containing alloys in a frequency range up to 400 kHz and magnetic induction up to 0.8 T.

Magnetic properties evolution and crystallization behaviour of vacuum- and air-long-term-annealed rapidly quenched Fe80.3Co5Cu0.7B14 alloy.

This work aims to investigate the isothermal crystallization behaviour, crystal structure and magnetic properties evolution of long-term (up to 300h) low temperature (210 and 260°C) vacuum- and air-annealed Fe80.3Co5Cu0.7B14alloy. Before the α-Fe(Co) phase crystallization, the primary relaxation process has been identified at a temperature range up to 340°C. The relaxation process performed under 210°C for 300h did not initiate the crystallization process. However, the topological and compositional short-range rearrangements improved magnetic properties remarkably. Annealing 150h at 260°C helps to deliver enough energy to stabilize the glassy state and initiate the crystallization process fully. Structural and magnetic properties evolution of 150h annealing at 260°C corresponds to the evolution presented during isochronal 20min annealing at 310°C. Magnetic properties Bs = 1.75-1.79T, Hc < 20 A/m and P10/50are similar to those for 20min of annealing at 310°C. Comparison of core power losses from up to 400kHz frequency dependences of long-term low temperature annealed alloy with 20min classical annealing at 310°C shown that presented here long-term annealing is energetically insufficient to bring the glassy state system into the same low level of core power losses efficiency.

Soft magnetic composites based on Fe fibres and powders prepared by cold sintering process

The manuscript provides a new strategy for preparation of soft magnetic composites that involves the consolidation of the ferromagnetic phase (fibres or powders), which is first covered with an insulating layer, via the cold sintering process. The manuscript reports on the preparation and characterisation of cold sintered compacts based on Fe fibres and Fe powders coated with ZnO and sintered at the temperature of 200 °C for 60 min under the pressure of 600 MPa. The amount of ZnO used as dielectric phase was 10 and 20 wt%. The absence of any reaction between phases that compose the compacts (Fe fibres or powders and ZnO) during the cold sintering process was proved by X-ray diffraction (XRD). Electron microscopy and X-ray micro-analysis (SEM-EDX) were used for morphology and chemical analysis of the cold sintered compacts. The influence of the type of ferromagnetic phase (fibres or particles), as well as the influence of the amount of dielectric phase on the saturation induction (Bs), the coercive field (Hc), and the maximum relative permeability (µrmax) of the cold sintered magnetic cores, was investigated and discussed. The effect of the same factors on the total core power losses (P) and the initial relative permeability (µri) of the cold sintered compacts, upon increasing the frequency of the magnetising field up to 10 kHz, was analysed. The feasibility of applying a heat treatment at the temperature of 450 °C for 1 h was investigated, leading to the enhancement of both DC and AC magnetic properties of the cold sintered compacts.

Reduction of the core size and power losses by using soft magnetic material for a single-phase induction motor

Induction motors are widely used in our daily life and industrial machines. Single-phase induction motors with small power, manufactured with few horsepowers (HP), are preferred as compressor motors for household refrigerators and air conditioners. This inevitably leads to the lower energy consumption of compressor systems and requirements for a more compact design. In this study, a single-phase induction motor manufactured with classical core material for a certain power value is modeled using finite element analysis (FEA) software and the power losses are investigated. Later, this electric motor is designed with 6.5% SiFe jfe super core material, one of the soft magnetic core materials, for the same power value and comparative performance studies are performed. In these comparisons, mechanical volume and weight for the motor dimensions, electrical power losses and electromagnetic parameters are studied. It is therefore recommended that the jfe super core material, which has become popular in recent years, be used for the manufacture of single-phase induction motors, which are often used in household appliances.

Structure and Magnetic Properties of Thermodynamically Predicted Rapidly Quenched Fe85-xCuxB15 Alloys.

In this work, based on the thermodynamic prediction, the comprehensive studies of the influence of Cu for Fe substitution on the crystal structure and magnetic properties of the rapidly quenched Fe85B15 alloy in the ribbon form are performed. Using thermodynamic calculations, the parabolic shape dependence of the ΔGamoprh with a minimum value at 0.6% of Cu was predicted. The ΔGamoprh from the Cu content dependence shape is also asymmetric, and, for Cu = 0% and Cu = 1.5%, the same ΔGamoprh value is observed. The heat treatment optimization process of all alloys showed that the least lossy (with a minimum value of core power losses) is the nanocomposite state of nanocrystals immersed in an amorphous matrix obtained by annealing in the temperature range of 300–330 °C for 20 min. The minimum value of core power losses P10/50 (core power losses at 1T@50Hz) of optimally annealed Fe85-xCuxB15 x = 0,0.6,1.2% alloys come from completely different crystallization states of nanocomposite materials, but it strongly correlates with Cu content and, thus, a number of nucleation sites. The TEM observations showed that, for the Cu-free alloy, the least lossy crystal structure is related to 2–3 nm short-ordered clusters; for the Cu = 0.6% alloy, only the limited value of several α-Fe nanograins are found, while for the Cu-rich alloy with Cu = 1.2%, the average diameter of nanograins is about 26 nm, and they are randomly distributed in the amorphous matrix. The only high number of nucleation sites in the Cu = 1.2% alloy allows for a sufficient level of grains’ coarsening of the α-Fe phase that strongly enhances the ferromagnetic exchange between the α-Fe nanocrystals, which is clearly seen with the increasing value of saturation induction up to 1.7T. The air-annealing process tested on studied alloys for optimal annealing conditions proves the possibility of its use for this type of material.

EVALUATION OF FAULTS IN THE SQUIRREL CAGE THREE-PHASE INDUCTION MOTORS

Induction motors have played a central role in the techno-economic development of modern industries and electric power generation. However, the presence of recurring failures hinders a cost-effective performance and leads to catastrophic damage. Therefore, the present study proposed an assessment to investigate the influence of two types of failures in induction motors, namely failure due to broken bars in the rotor and defects in the connection between the rotor bars and the end ring. Accordingly, a three-phase induction motor was evaluated under different failure conditions that modified the operational torque and rotational speed. The results indicated that both types of failures magnify both the core and copper power losses by up to 13.3 % and 8 %, respectively, compared to the healthy condition. On the other hand, an efficiency reductionbetween 1.94 % to 3.41 % is an indication of failure progression. Finally, the appearance of harmonics 3 and 7, and the intensified magnitude of harmonic 5, represent a clear sign of failure occurrence related to rotor barsand defects in the connection to the end ring. In conclusion, the proposed methodology proved to be an adequate tool to predict failure appearance, which has a direct impact on extending the lifetime of induction motors.

Improved Spice Simulation of Dynamic Core Losses for Ferrites With Nonuniform Field and Its Experimental Validation

This article presents a SPICE circuit that is able to predict dynamic core losses in ferrite inductors with nonuniform magnetic field. The circuit is supplied by a current generator and provides the core power loss as output. The article moves from models available in literature, which has been modified by the introduction of two main improvements allowing to extend the fields of applications. The first one is the design of a circuit that is able to ensure accurate power losses estimation even in the presence of signals affected by noise. The second improvement extends the usability of the model also to those cases where the magnetic material saturates because of high current or temperature effect. Extensive experimental tests to assess the accuracy of the estimations and simulations have been carried out.

A Saturated Amorphous Alloy Core-Based Inrush Current Limiter to Eliminate Inrush Currents and Restrain Harmonics during Transformer Energization

In this paper, a new saturated amorphous alloy core-based inrush current limiter (ICL) has been designed and built to limit the inrush current of a power transformer. A toroidal core with a middle limb is developed using the Metglas amorphous alloy and the middle limb is excited with a dc current to saturate the amorphous alloy core. Only a very small dc excitation current is required using such a core when compared to that using a similar design with conventional materials. Under normal conditions, the saturated amorphous alloy ICL core steady-state impedance is low and has a negligible effect on the operation of the system. During the energization of a power transformer connected to the ICL, the large inrush current de-saturates the amorphous alloy core, resulting in an increase in the ac winding impedance, which limits the peak amplitude of the transformer inrush current and harmonics. To validate the proposed saturated amorphous alloy core-based ICL, a prototype ICL has been built and tested in the laboratory. The experimental results show that the core power loss, core saturation, the fundamental and harmonics of the inrush current of the proposed saturated amorphous alloy core-based ICL are significantly better compared with those from the sheet steel core-based ICL. It is expected that the proposed saturated amorphous alloy core will be used in future inrush current limiters that can help to improve the performance of the power transmission and distribution system.

Influence of Cu Content on Structure, Thermal Stability and Magnetic Properties in Fe72-xNi8Nb4CuxSi2B14 Alloys.

The effect of substitution of Fe by Cu on the crystal structure and magnetic properties of Fe72−xNi8Nb4CuxSi2B14 alloys (x = 0.6, 1.1, 1.6 at.%) in the form of ribbons was investigated. The chemical composition of the materials was established on the basis of the calculated minima of thermodynamic parameters: Gibbs free energy of amorphous phase formation ΔGamorph (minimum at 0.6 at.% of Cu) and Gibbs free energy of mixing ΔGmix (minimum at 1.6 at.% of Cu). The characteristic crystallization temperatures Tx1onset and Tx1 of the alpha-iron phase together with the activation energy Ea for the as-spun samples were determined by differential scanning calorimetry (DSC) with a heating rate of 10–100 °C/min. In order to determine the optimal soft magnetic properties, the wound cores were subjected to a controlled isothermal annealing process in the temperature range of 340–640 °C for 20 min. Coercivity Hc, saturation induction Bs and core power losses at B = 1 T and frequency f = 50 Hz P10/50 were determined for all samples. Moreover, for the samples with the lowest Hc and P10/50, the magnetic losses were determined in a wider frequency range 50 Hz–400 kHz. The real and imaginary parts of the magnetic permeability µ′, µ″ along with the cut-off frequency were determined for the samples annealed at 360, 460, and 560 °C. The best soft magnetic properties (i.e., the lowest value of Hc and P10/50) were observed for samples annealed at 460 °C, with Hc = 4.88–5.69 A/m, Bs = 1.18–1.24 T, P10/50 = 0.072–0.084 W/kg, µ′ = 8350–10,630 and cutoff frequency at 8–9.3 × 104 Hz. The structural study of as-spun and annealed ribbons was carried out using X-ray diffraction (XRD) and a transmission electron microscope (TEM).

Modified Preisach Model of Hysteresis in Multi Air Gap Ferrite Core Medium Frequency Transformer

This article presents the modified Preisach model of hysteresis for a 3-phase medium frequency transformer in a 100 kW dual active bridge converter. The transformer magnetic core is assembled out of ferrite I-cores, which results in multiple parasitic air gaps. For this transformer, the hysteresis loops were measured and parameters of the Preisach model were determined. The Preisach distribution function is approximated with a two-dimensional Gauss function series and the feedback function is a 3rd-degree polynomial. The optimized identification of Preisach distribution function parameters was prepared. Two sets of parameters were determined based on the analysis of major and minor hysteresis loop. The developed model is used to analyze the transformer core power loss. A new set of Steinmetz equation parameters for multi air gap ferrite core MFT is proposed.

The Structure and Magnetic Properties of Rapidly Quenched Fe72Ni8Nb4Si2B14 Alloy.

The complex structural and magnetic studies of the annealed rapidly quenched Cu-free Fe72Ni8Nb4Si2B14 alloy (metallic ribbons form) are reported here. Based on the calorimetric results, the conventional heat treatment process (with heating rate 10 °C/min and subsequent isothermal annealing for 20 min) for wound toroidal cores has been optimized to obtain the least lossy magnetic properties (for the minimum value of coercivity and magnetic core losses at 50 Hz). For optimal conditions, the complex permeability in the 104–108 Hz frequency range together with core power losses obtained from magnetic induction dependence up to the frequency of 400 kHz was successfully measured. The average and local crystal structure was investigated by the use of the X-ray diffraction method and the transmission electron microscopy observations and proved its fully glassy state. Additionally, for the three temperature values, i.e., 310, 340 and 370 °C, the glass relaxation process study in the function of annealing time was carried out to obtain a deeper insight into the soft magnetic properties: magnetic permeability and cut-off frequency. For this type of Cu-free soft magnetic materials, the control of glass relaxation process (time and temperature) is extremely important to obtain proper magnetic properties.

Per-Unit Hysteresis and Eddy Loss Method Based on 3D Finite Elements for Non-Symmetric Toroidal Magnetic

Several main methodologies are used to estimate the core power loss (CPL) in magnetic components. One group is based in the Steinmetz equation (The modified one, the generalized one and the natural equations are the principals). Another one is the separation of losses between hysteresis, eddy current and excess losses. The third group is based mathematical-empirical hysteresis models and the last one is based on the magnetization process. These approaches need a prior test or analysis to calculate the CPL. Tests are usually expensive, or the number of needed tests is excessive for the component design process. 2D analyses are not enough for some magnetic components due to their lack of symmetries. Toroidal core components are ones of the most common components in transformers and power converters. They do not have symmetries in the magnetic field distribution and only 3D models are satisfactory to take into account all the effects and phenomena. An extensive study of 3D model finite element analysis was developed to determine the main losses in magnetic components core, the hysteresis and eddy current losses. A new methodology is presented, per-unit CPL (considering only Hysteresis and Eddy Current Losses) that permits analyzing the impact of the involved factors separately. The proposed per-unit CPL allows the definition of a new equation for determining hysteresis and eddy current losses using only the geometrical and material parameters (core and coils) used to estimate the total CPL.

Grain boundary engineering of power inductor cores for MHz applications

In this article we present the latest trends in processing, composition, theory, and utility of spinel ferrites for use as power inductor cores for a wide range of applications including power generation, conversion, and conditioning at MHz frequencies. Furthermore, it is a principle goal of this article to examine state of the art approaches and innovative methodologies to engineer grain boundary regions in composition, structure, and electrical and magnetic properties that allow spinel ferrites to operate at frequencies well above the state of technology (i.e., f > 1 MHz) with low core power loss while concomitantly maintaining high efficiency, high permeability and saturation induction.

Review of Core Power Loss Analysis Using Finite Element Methods

There are two principal methods are utilized to estimate the core power loss (CPL) in magnetic components: Empirical equations and hysteresis models. Both approaches need an anterior test or analysis to calculate the CPL. Most of them are based on improved Steinmetz equations. Tests are usually costly or the number of necessary tests is excessive for the component design development. 2D analyses using Finite Element are not good enough for several magnetic components for their lack of symmetries.

Effects of the sodium stearate addition on the corrosion resistance and electromagnetic properties of phosphatized iron-based SMCs

Abstract The surface modification effects on the corrosion resistance and electromagnetic properties of iron-based soft magnetic composites (SMCs) were investigated in this study. Sodium stearate surface modification improved the mixing compatibility between phosphatized iron powder and epoxy resin. Sodium stearate reduces the friction between particles and between the particles and die wall during compaction. Reduced friction thereby increases the compaction density and abrasion resistance. The initial permeability was decreased with increasing sodium stearate concentration. The phosphatized iron powders with sodium stearate surface modification possessed lower imaginary permeability and core power loss than samples without surface modification.

Analysis and Design of Choke Inductors for Switched-Mode Power Inverters

This paper presents the design, analytical estimation of power losses, and experimental measurement of choke inductors for switched-mode power inverters. The described approach is applicable to a wide variety of circuits such as Class-E inverters and converters. The expressions required to design the magnetic core in the choke inductor using the area–product ( $A_p$ ) method are given. The equations for the dc resistance, ac resistance at high frequencies, and dc and ac power losses are provided for the solid round winding wire. To validate the presented approach, an example class-E zero-voltage switching power inverter with practical specifications is considered. A core with air gap is selected to avoid core saturation in the choke inductor, which conducts dc current and a small ac current. The gapped core power loss density and power loss are estimated using Steinmetz empirical equation. It is shown that the winding power loss due to the dc current is dominant for the given design. A comparison between the area–product $A_p$ method and the preexisting core geometry coefficient $K_g$ method is presented. The measured magnitude of the inductor impedance has shown that the designed choke is useful up to ten times the switching frequency.

Concurrent Core Loss Suppression and High Permeability by Introduction of Highly Insulating Intergranular Magnetic Inclusions to MnZn Ferrite

A novel approach entailing the introduction of incongruent insulating magnetic inclusions to the grain boundary region of polycrystalline ferrite cores has been proposed to target the eddy current loss as the major source of core loss at high operating frequency. To demonstrate the efficacy of this approach, highly resistive ferrimagnetic nanoparticles (NPs) of yttrium iron garnet (YIG) were introduced to the grain boundaries of MnZn ferrite. Diamagnetic NPs of barium titanate (BTO) were similarly added as a nonmagnetic insulating grain boundary control additive. A profound decrease was observed in the eddy current loss (up to 79%) by using this approach. For the case of magnetic inclusions, a retained high permeability (24% reduction) was achieved, whereas the samples with nonmagnetic additives experienced a considerable sacrifice to permeability (64% reduction). The sustained high permeability was attributed to the ferrimagnetic YIG NPs maintaining long-range magnetic interactions, whereas the BTO NPs both frustrated the eddy current and long-range intergranular magnetic interactions. These results indicate that low permeability is no longer a necessary constraint for suppression of core power loss.

Remagnetization Core Losses In The Massive Amorphous FeCoYb Alloy

In this paper were studied the influence of magnetic field frequency and induction on the total core power loss � which is divided into eddy current loss, hysteresis loss and anomally losses of the bulk amorphous alloy. The total core power loss of the investigated bulk amorphous alloy increases with magnetic field frequency and peak induction. It follows a power relation similar to what has been observed in classical ribbons. In the investigated alloy in addition to losses due to magnetic hysteresis and eddy currents, other additional losses are present. However additional losses, emerging simultaneously to the component associated with migration relaxations are very weakly dependent on the frequency and temperature.

Sensitivity of effective relative permeability for gapped magnetic cores with fringing effect

Magnetic component tolerances are caused by variations in air-gap and core relative permeability. This study presents the derivation for sensitivity of effective relative permeability to variations in the relative core permeability and relative gap length for magnetic cores with and without fringing effect. The expressions for the fringing factor and effective relative permeability for the magnetic cores have been derived. The effect of air-gap on the core properties, which includes core power loss density, magnetic flux density, and magnetic field intensity is addressed for cores used in low-frequency and high-frequency applications. An example core is selected to support the theoretical predictions. The expressions to determine the inductor tolerances are presented.

Steinmetz Equation for Gapped Magnetic Cores

This letter presents a derivation of the modified Steinmetz empirical equation for power loss density and power loss in magnetic cores with air gaps. The modified Steinmetz equation relates the core power loss density with the air gap length, magnitude and frequency of the sinusoidal excitation current, and the permeability of the core material. The reluctance model of a representative core structure is used. The expression for the magnetic field density in gapped cores is derived. In addition, the minimum air gap length required to avoid core saturation is determined. The modified Steinmetz equation for power loss is analyzed using the specifications of a practical magnetic core used in high-frequency applications. The effect of the air gap length and the excitation frequency on the core power loss density is discussed.