Core Vibration Research Articles

Vibration Reduction of Inductors Under Magnetostrictive and Maxwell Forces Excitation

This paper analyzes the phenomenon of vibrations in U-shaped (two-limb) inductors with distributed air gaps due to both Maxwell and magnetostriction forces. A weak 2-D magnetomechanical finite-element model (FEM), including magnetostrictive tensor, is developed under the GetDP open-source simulation environment. A simple analytical model of the reactor core vibration under magnetic forces is established and validated using the FEM model. The resonance effect of magnetostriction and Maxwell forces on the inductor structure is analyzed, and a sensitivity analysis is run on some of the inductor geometrical parameters. An example of inductor is presented, and a methodology to reduce vertical vibrations under magnetic force excitation is proposed by opposing the magnetostrictive and Maxwell forces. This technique is validated using both the analytical and the FEM models.

Effects of Multicore Structure on Magnetic Losses and Magnetomechanical Vibration at High Frequencies

This paper investigates the magnetic properties of Fe-based amorphous material Metglas® 2605-HB1, SA1, and new high induction HB1-M amorphous material around 1.64 Tesla, which one of core component structured with hybrid thin film materials is obtained. Different core types in constructive modeling and magnetic field simulation are studied by the finite element method (FEA). According to the simulation results, the magnetic flux lines passing through different bending angles of core corners have induced different magnetic performances. Results suggest that a long and straight core leg for a multi-angled core can help to reduce magnetostriction variation, which the multi-angles of core corners to be an important factor in the reduction of magnetostriction variation and improving magnetic property. The experimental results in magnetism of the core are shown at different frequencies ranging from 60 Hz to 3000 Hz. The magnetism of the triangular core is significantly better than that of its counterpart, the multi sharp-angled structure, demonstrating less significant reductions of the magnetic properties in terms of core loss, core vibration, and sound level. In addition, a hybrid-type core structure with NHI material is used to both improving magnetic properties while reducing magnetic loss; however, magnetism in terms of sound level and core vibration is shown to be difficult to control. Actually, it is well-know that the ferrite core construct with multi-cored structure would reduce the eddy current loss due to the stacking process in laminated silicon-steel cores. According to the experimental results, it has shown the difference in eddy current field for soft material is not only the key factor in both of the resistance and permeability factor, actually, but also decided by the permittivity. It is interested the soft material has increased the frequencies form hundred to kilohertz, for iron-based material, the hysteresis loss in magnetic power loss is significant, but, the eddy current loss is much more smaller due to the lower conductivity of amorphous material. Therefore, the reduction in magnetic core loss for multi-cored structure is significant to reduce the loss due to different core structure in permittivity.

Reduction of Vibration and Sound-Level for a Single-Phase Power Transformer With Large Capacity

This paper presents the reduction of noise and vibration concerning the magnetostriction effects for a single-phase power transformer with a large capacity of 200 MVA. Two magnetic core shapes are investigated: 1) D-yoked core and 2) square-yoked core. The D-yoked core is used for the construction of the transformer prototype in this paper. The magnetostriction and the hysteresis loop of the core material are measured for the simulation and analysis of noise and vibration. The transformer prototype is assembled with an external clamping force applied on the core, and the core vibration and sound-level are observed. The transformer operates with a periodic excitation that may induce resonance in the core. To avoid this, a finite-element analysis is used for modal analysis to identify the natural frequencies of the core. A tank is also designed with a sufficiently rigid structure to avoid resonances. The sound-level of the fully assembled transformer prototype is measured, and it is found to have a low-noise level below 65 dB.

Suppressing magneto-mechanical vibrations and noise in magnetostriction variation for three-phase power transformers

This study investigated the effect of magnetostriction-induced core magnetomechanical vibrations and noise on the magnetic properties of power transformers. The magnetostriction of grain-oriented Si steels was found to be extremely sensitive to compressive stress applied along the rolling direction and to tensile stress applied along the transverse direction. The compressive stress increased the variation in the magnitude of magnetostriction, which is correlated with core vibration and noise. A 2D model of the power transformer was used to simulate the noise and vibration variables through a finite element analysis.

Research on the Vibration Condition On-Line Monitoring System for EHV Power Transformer

The paper introduces a design scheme for the Extra High Voltage (EHV) transformer condition on-line monitoring system, which is based on the collection and analysis of the transformer winding and core vibration signals. This system is composed of vibration acceleration signal sensors and the signal analyzing computer where the collected vibration signal is saved and processed. The analyzing computer can accomplish the missions of data acquisition control, data analysis and the historical data query. Vibration characteristic values of transformer winding and core include peak to peak value, spectrum, kurtosis, and the amplitude 100Hz component and its higher harmonic components. They are extracted, and the characteristic trend curves are drawn by data analysis, so that EHV transformer on-line monitoring and fault diagnosis are accomplished.

三相変圧器鉄心の三次元振動解析

The 3D vibration and 3D magnetostriction of a model transformer core made up of grain-oriented electrical steel sheets were studied by using laser Doppler vibrometry, an accelerometer and strain gauges. The following results were obtained. The magnetostriction of the transformer core at the T-joint and the corner area including the joint part displayed several times larger amplitude than that of a single sheet under sinusoidal excitation. The out-of-plane vibration of the transformer core showed a much larger amplitude than the in-plane vibration. It is considered that the out-of-plane vibration was the main cause of acoustic noise. The amplitude of in-plane vibration of the core can be explained for the magnetostriction amplitude in the in-plane direction. On the other hand, the out-of-plane vibration was tens of times larger than the vibration calculated from the magnetostriction amplitude in the out-of-plane direction. Furthermore, the same result, that out-of-plane vibration is larger than in-plane vibration, was also obtained by measuring a practical transformer core, and the frequency spectrum of acoustic noise presented a similar frequency spectrum to that of out-of-plane vibration.

Multi-field Coupling Simulation and Experimental Study on Transformer Vibration Caused by DC Bias

DC bias will cause abnormal vibration of transformers. Aiming at such a problem, transformer vibration affected by DC bias has been studied combined with transformer core and winding vibration mechanism use multi-physical field simulation software COMSOL in this paper. Furthermore the coupling model of electromagnetic-structural force field has been established, and the variation pattern of inner flux density, distribution of mechanical stress, tension and displacement were analyzed based on the coupling model. Finally, an experiment platform has been built up which was employed to verify the correctness of model.

Study on the Characteristics of Low-Frequency Vibration of the Core of Single Phase Transformer Set Caused by GIC

The study on characteristics of transformer vibration caused by GIC is the foundation of studies on transformer noise caused by GIC, location selection of monitoring vibration and noise. In this study, the characteristics of low-frequency vibration of the core of single phase transformer sets caused by GIC have been analyzed through building mathematical models and experimental analysis. The results show that when DC bias occurs the vibration signals contain 50 Hz and 150 Hz vibration. With the degree of DC bias the 50 Hz vibration grows by linear increase and 150 Hz vibration grows by square increase. Affected by GIC, the 50 Hz and 150 Hz vibration waveform’s phase changes with alternate 0 andπ. The characteristics of 50 Hz and 150 Hz vibration discriminate between core vibration caused by GIC and HVDC grounding currents. This study has significance for vibration monitoring of transformer faults, and can assist in determining the level of GIC.

Nonlinear free vibration of core–shell nanowires with weak interfaces based on a refined nonlocal theory

Based on a refined nonlocal theory, the nonlinear free vibration of core–shell nanowires is presented in this paper. This refined model can predict the weakening of interfacial bonding which satisfies the vanishing stress boundary condition at surface and stress continuity conditions at the interface. The nonlinear governing equations and boundary conditions are obtained by using Hamilton’s principle. The whole problem is solved by a second-step perturbation technique. In numerical results, the simply supported core–shell nanowire with inplane immovable is considered. The effects of transverse shear deformation, geometric sizes, and small-scale parameter and interfacial shear stiffness are discussed.

BOX Ligands in Biomimetic Copper‐Mediated Dioxygen Activation: A Hemocyanin Model

AbstractThe μ‐η2:η2‐peroxodicopper(II) core found in the oxy forms of the active sites of type III dicopper proteins have been a key target for bioinorganic model studies. Here, it is shown that simple bis(oxazoline)s (BOXs), which are classified among the so‐called “privileged ligands”, provide a suitable scaffold for supporting such biomimetic copper/dioxygen chemistry. Three derivatives R,HBOX‐Me2 (R = H, Me, tBu) with different backbone substituents have been used. Their bis(oxazoline)‐copper(I) complexes bind dioxygen to yield biomimetic μ‐η2:η2‐peroxodicopper(II) species. O2 can be reversibly released upon an increase in temperature. Their formation kinetics have been studied under cryo‐stopped‐flow conditions for the tBu derivative, giving activation parameters ΔH‡on = (2.27 ± 0.18) kcal mol–1, ΔS‡on = (–46.3 ± 0.8) cal K–1 mol–1 for the binding event and ΔH‡off = (11.7 ± 1.9) kcal mol–1, ΔS‡off = (–16.1 ± 8.2) cal K–1 mol–1 for the release of O2, as well as thermodynamic parameters ΔH° = (–10.0 ± 1.7) kcal mol–1 and ΔS° = (–32.7 ± 7.4) cal K–1 mol–1 for this equilibrium. The μ‐η2:η2‐peroxodicopper(II) complexes have been isolated as surprisingly stable solids and investigated in depth by a variety of methods, both in solution and in the solid state. Resonance Raman spectroscopy revealed a characteristic isotope‐sensitive stretch $\tilde {\nu}$O–O = 731–742 cm–1 (Δ[18O2] ≈ –39 cm–1) and an intense feature around 280 cm–1 diagnostic for the fundamental symmetric Cu2O2 core vibration. A slight butterfly‐shape of the Cu2O2 core has been derived from EXAFS data and DFT calculations. SQUID magnetic data evidenced strong antiferromagnetic coupled CuII2 (–2J ≥ 1000 cm–1). Thermal degradation in solution yields bis(hydroxo)‐bridged [(tBu,HBOX‐Me2)(L)Cu(OH)]2(PF6)2 (L = H2O, MeCN or THF); whereas in the case of H,HBOX‐Me2, ligand oxygenation has been detected. Preliminary reactivity studies with the substrate 2,4‐di‐tert‐butylphenol indicate the formation of the C–C coupling product 3,3′,5,5′‐tetra‐tert‐butyl‐2,2′‐biphenol, whereas ortho‐hydroxylation was not observed. The copper(I) complex [(tBu,HBOX‐Me2)Cu(MeCN)]PF6 as well as two dicopper(II) complexes [(L)(tBu,HBOX‐Me2)Cu(OH)]2(PF6)2 have been characterised by single‐crystal X‐ray diffraction. Considering the vast number of known BOX derivatives, a rich and versatile Cu/O2 chemistry based on this platform is anticipated.

Study on DC Bias Vibration Signal Separation and Experiment of Transformer Based on FAST-ICA Algorithm

Transformer vibration research is an effective diagnosis of DC bias fault. The vibration signal acquired is actually the mix signal of vibration from both the core and windings, and this makes it difficult to analyze the above two separately. Therefore the paper presents a new approach to separate vibration signal of core and windings by Fast-ICA algorithm. The simulated results of core and windings vibration are given and compared with experiment test. Comparative analysis verify that transformer vibration in no-load is core vibration and vibration in short circuit is windings vibration. Transformer vibration signals under different DC bias are tested by experiment. Vibration signals are separated by Fast-ICA algorithm. Core vibration signal and windings vibration signal are respectively obtained. The research lays the groundwork for further research of transformer DC bias vibration.

Identification of Transformer Core Vibrations and the Effect of Third Harmonic in the Electricity Grid

In this work, an experimental technique is applied for the measurements of the vibrations and deformation of a test transformer core. Since the grid voltage contains some higher harmonics, in addition to a purely sinusoidal magnetisation of the core the presence of third harmonic is also studied. The vibrations of the transformer core for points as well as the surface scan of the leg show more deformation in the corners of the leg than the middle of the leg. The influence of the higher harmonic of the magnetisation on the core deformation is also more significant in the corners of the leg. The core deformation shape under a sinusoidal magnetisation with a higher harmonic is more wavy and fluctuating than that under a purely sinusoidal magnetisation.

Identification of the vibrational modes in the far-infrared spectra of ruthenium carbonyl clusters and the effect of gold substitution.

High-quality far-IR absorption spectra for a series of ligated atomically precise clusters containing Ru3, Ru4, and AuRu3 metal cores have been observed using synchrotron radiation, the latter two for the first time. The experimental spectra are compared with predicted IR spectra obtained following complete geometric optimization of the full cluster, including all ligands, using DFT. We find strong correlations between the experimental and predicted transitions for the low-frequency, low-intensity metal core vibrations as well as the higher frequency and intensity metal-ligand vibrations. The metal core vibrational bands appear at 150 cm(-1) for Ru3(CO)12, and 153 and 170 cm(-1) for H4Ru4(CO)12, while for the bimetallic Ru3(μ-AuPPh3)(μ-Cl)(CO)10 cluster these are shifted to 177 and 299 cm(-1) as a result of significant restructuring of the metal core and changes in chemical composition. The computationally predicted IR spectra also reveal the expected atomic motions giving rise to the intense peaks of metal-ligand vibrations at ca. 590 cm(-1) for Ru3, 580 cm(-1) for Ru4, and 560 cm(-1) for AuRu3. The obtained correlations allow an unambiguous identification of the key vibrational modes in the experimental far-IR spectra of these clusters for the first time.

Fe-based composited cores for single-phase transformers fabricated with high-induction amorphous material

A composite-structured, high-induction, double-layered soft magnetic composite core (SMC) comprised of magnetic amorphous HB1-M, HB1, and SA1 materials was developed. A finite element analysis simulated results for the magnetic loss and magnetic flux density for three types of amorphous cores are quite different from findings for traditional magnetic core structures, such as laminated silicon steel, because the magnetostriction and permeability properties of composite-laminated no-cutting structures can be restrained. The SMC structure showed interesting results for magnetic loss, magnetic flux lines, core vibration, and sound level. The main advantage of transformers assembled with composited-cores of SA1 and HB1 over a higher-induction core single-phase transformer is the significant reduction of magnetic loss. However, the SA1 and HB1 composite core also showed worse results in terms of vibration and sound level because the magnetostriction and magnetic flux density in the core distribution are not quite identical to the results for other core types.

Effects of magnetostriction and magnetic reluctances on magnetic properties of distribution transformers

This paper analyzes the causes of magnetic reluctance in silicon steel wound cores with multi step-lapped joint structures through the appropriate exploitation of simulated and experimental local flux distributions in an air-gapped core, to propose techniques that can enable the reduction of the resulting core loss and vibration. The magnetic magnetostriction forces in the lap-joint regions, constituting another significant source of permeability, can be controlled by rearranging the step-lapped joint structure. Then, the computed local flux distributions were compared with experimental data. Single-phase pad-mounted distribution transformers with a capacity of 167 kVA were used in this study. It is indicated that the multi-step lap joint can significantly reduce the core loss and exciting power by regulating the configuration of adjacent air-gapped distances. Finally, composite-core structures were also used to validate the reduction of magnetostriction, core loss, and vibrations, corresponding to single-phase distribution transformer.

Measurement and Modeling of Anisotropic Magnetostriction Characteristic of Grain-Oriented Silicon Steel Sheet Under DC Bias

Magnetostriction in grain-oriented (GO) electrical silicon steel arises vibration and noise of the transformer core, especially when operating under direct current (dc) bias. In this paper, the anisotropy of magnetostriction of GO silicon steel sheets along the rolling direction (RD) and other directions deviated from RD was measured based on a standard single-sheet measurement system. The effect of applied stress on magnetostriction was also measured and analyzed. The magnetostriction under alternating magnetic field plus dc biased field was measured and a constitutive equation considering single-valued curves of magnetostriction under dc bias when incorporated with magnetic finite-element analysis was investigated. Considering a simple model as an example, the effectiveness of the proposed modeling method was verified by the comparison of simulation data and measured ones.

Contribution of Magnetostriction to Transformer Core Vibration under DC Bias

An important source of transformer core vibration is magnetostriction of the thin silicon-steel lamination. In the power grid, direct current (DC) may form by solar magnetic storms and DC transmission. Transformer core supersaturation and harmonic increase in current caused by DC bias will intensify magnetostriction and produce additional transformer core vibration. In order to obtain transformer core vibration under DC bias, the magnetization curve and magnetostriction characteristics of thin silicon-steel lamination are measured. Then, this paper establishes a numerical magneto-mechanical strong coupling model including magnetostrictive effect under DC bias for three-phase three-column dry transformers. On the basis of the proposed model, and the measured magnetic characteristics of the thin silicon-steel lamination, transformer core vibration under DC bias and no-load condition has been calculated. In order to verify the proposed model, transformer core vibration under DC bias and no-load condition is studied experimentally. Numerical calculation results together with experimental results confirm the validity of the proposed method.

Study of Winding Method to Reduce Stray Loss and Stator Core Vibration of Synchronous Machine

The fractional slot windings are widely used in rotating machine in order to increase the flexibility of design and improve the voltage waveform. However, the MMF wave of fractional-slot windings are found to contain unique harmonic components, which are designated as even space flux harmonics, fractional flux harmonics, or both. They may cause stray loss and stator core vibration. This paper proposes new winding methods such as “novel interspersed windings” and “expanded group windings” to reduce these harmonics. The advantages of two proposed winding methods are verified by using numerical analysis and measurement test of winding model.

Effect of Magnetostriction on the Core Loss, Noise, and Vibration of Fluxgate Sensor Composed of Amorphous Materials

This paper presents a new multistructure fluxgate magnetic sensor composed of Metglas® Fe-based amorphous HB1 material. The core thickness of the fabricated structure is 0.0254 mm × 30 pieces, and its width is 5 mm. The magnetic loss of the fluxgate core is simulated through finite element analysis. The fluxgate sensor is experimentally analyzed over a frequency range 0.5-3 kHz. The sensor performance exploits the advantages of the multistructure core-shaped magnetic material as well as the second-harmonic operation mechanism. Excellent flux responses are detected for the triangular core sensor, which has different operating frequencies for magnetostriction variation, harmonic response, total harmonic distortion, noise level, sensor vibration, and sensitivity. The influence of magnetostriction, magnetic loss, and permeability in multiangled cores for different frequencies is analyzed. Our multistructure fluxgate sensor is suitable for various applications including power transformer and inverter for interior magnetic core fault detection, owing to its thin-film configuration, high sensitivity, high resolution, and low magnetic loss.

A Reformative Simulation Method of Motor Pole Core Vibration Characteristics

As to directing motor design, it is very important to make sure that the motor’s forecast of vibration performance has reference value. So, it must need motor’s parts vibration characteristics simulation results are so close to their characteristics. This paper puts forward a new simulation method of motor pole core vibration characteristics, this method includes setting anisotropy material attributes multipartite, getting attributes parameters values which are based on recommended fitting curves, modeling and equating windings, equating dipping lacquer and so on. Combining with experiments, the new method is validated its availability.