Amplitude Of Magnetic Flux Density Research Articles

Underwater Cable Localization Method Based on Beetle Swarm Optimization Algorithm

Dear Editor, This letter concerns the localization of three-core underwater cables which are widely deployed for offshore energy transmission. It is a non-trivial problem, since the external magnetic field of three-core underwater cables is variable which reduces the accuracy of localization. To solve this problem, in this letter, an approximate equation is firstly derived to formulate the external magnetic field of a three-core armored underwater cable by considering the seafloor environments and the structure of three-core cables. Then, a new underwater cable localization method is proposed based on dual three-axis magnetic sensor array and the beetle swarm optimization (BSO) algorithm. The method constructs a fitness function based on the magnetic flux density amplitude and replaces the existing analytical geometry method with an optimization algorithm to achieve underwater cable localization with higher accuracy.

Accounting for Magnetic Saturation Effects in Complex Multi-harmonic Model of Induction Machine

Computations of quasi-dynamic electromagnetic field of induction machines using the complex magnetic vector potential require the use of the so-called effective magnetization curves, i.e., such in which the magnetic permeability is proportional to the amplitudes of magnetic flux density B or magnetic field strength H, not their instantaneous values. There are several definitions of that parameter mentioned in the literature provided for the case when B or H are monoharmonic. In this paper, seven different methods of determining the effective magnetization curves are compared in relation to the use of a field-circuit multi-harmonic model of an induction machine. The accuracy of each method was assessed by computing the performance characteristics of a solid-rotor induction machine. One new definition of the effective permeability was also introduced, being a function of multiple variables dependent on amplitudes of all the harmonics considered. The analyses demonstrated that the best practical approach, even for the multi-harmonic case, is to express the effective magnetic permeability as the ratio of the amplitudes of the fundamental harmonics of the magnetic flux density and the magnetic field strength, and assuming the sinusoidal variation of the latter.

A Fast and General Method to Calculate Mutual Inductance for EV Dynamic Wireless Charging System

For the electric vehicle (EV) dynamic wireless charging system, mutual inductance is an important factor affecting the output power. In this article, a fast and general method to calculate mutual inductance is proposed. This method can calculate the mutual inductance of magnetic couplers with different receiver structures and receiver positons by only one simulation, and it can also provide a theoretical guidance for the receiver design. Calculation models for different receiver structures are established, and the mutual inductance calculation-coefficients are proposed to describe the functional relationships between mutual inductance and receiver's parameters. Based on the concept of mutual inductance calculation-coefficients, the surface-integral in the conventional analytical calculation method can be simplified to be the product of these coefficients and magnetic flux density's amplitude, and then the calculation difficulty of the mutual inductance can be reduced. Finally, a prototype was built for experimental verification. The experiment results show that the max error between the measured mutual inductance and the calculated result is only 1.56%, which verifies the feasibility and the accuracy of the proposed calculation method.

Thermo-magnetic induced monodirectional periodic acoustic emission from free-standing nano-thin film

In this article, a thermally and magnetically induced monodirectional acoustic transducer is introduced with applications. An alternating thermal field is aroused by a sinusoidal current on a nano-thin film and an acoustic field is further excited due to the thermo-acoustic effect. A periodic magnetic field at the same frequency is concurrently applied to excite a fresh acoustic field in order to derive an enhanced sound pressure output. An analytical model for the mixed acoustic emitting system is established and the acoustic response is analyzed theoretically. An improved parabolic approximation relationship with only first-order Taylor's expansion is applied on the thermo-acoustic decoupling to obtain the thermo-acoustic propagating wave numbers. In addition, the oscillation of nano-thin film is driven by the magnetically induced Ampère's excitation in magneto-acoustics that introduces an additional mass effect. Moreover, thermo-acoustic and magneto-acoustic responses share the identical frequency but in a distinct phase difference. By designing a proper system configuration on the amplitude and phase of magnetic flux density, the backside acoustic field can be made to disappear. Furthermore, non-dimensionalization and numerical methods are applied to determine the amplitude of magnetic flux density for monodirectional acoustic field in varying parameters.

Acceleration effects in MDI magnetogram data

Acceleration effects are found in the Michelson Doppler Imager (MDI) magnetogram data because changes in the line profiles during the 30-s measurement are introduced by underlying p-mode velocity variations. This imparts an oscillatory component to the magnetic flux signal. Simulated profiles using Maltby M and Harvard Smithsonian Reference Atmospheres (HSRA) are shifted in accordance with a given velocity amplitude and period and the MDI algorithm for data measurement is applied. The simulated oscillatory component to the magnetic flux density always has a phase difference with respect to the underlying velocity of −90◦. The maximum introduced RMS amplitude is a function of velocity amplitude and field strength, but realistic errors are on the order of 5/2000 G, or 0.25% of field strength. Comparison of simulations with observations shows RMS amplitudes of MDI flux density are much greater than predicted by this effect. A 2-component HSRA model, tested to determine if stronger fields with smaller fill factors could fit the data, still can not reproduce the observations. It is concluded that oscillatory amplitudes of magnetic flux density measured with MDI are not due to acceleration effects, although the effect could contribute up to 25% of the measured amplitude. Attempts to remove acceleration effects from the magnetic flux signal are not successful. Also, we confirm that velocities measured in linearly polarized light in the vicinity of a strong magnetic field contain larger errors than velocities measured in circularly polarized light (Yang and Norton, 2001).

The photomagneton B(3) and longitudinal ghost field B(3) of electromagnetism

The concepts are introduced of the longitudinal ghost fieldB(3) and photomagnetonB(3)) of electromagnetism:B(3) = 〈B(3)〉 =B(0)〈Ĵ〉/ħ, whereB(0) is the magnetic flux density amplitude andĴ the angular momentum operator of a photon beam. The major implication is that the individual photon hasthree degrees of polarization, the longitudinal one being accompanied by the ghost fieldB(3) which has no energy or linear momentum, and is generated from the angular momentum of the photon.

Considerations on the relationship between distributed capacitance and iron loss in high-voltage transformers

This paper describes the results of an analysis on the relationship between distributed capacitance and iron loss in a high-voltage transformer applied to a push-pull current-fed converter in a high-voltage power supply. There are two operating modes in a push-pull current-fed converter; a boost mode and buck mode. In both modes, the maximum amplitude of magnetic flux density in the transformer decreases with increasing distributed capacitance. The reason for this is that the product of the transformer voltage and time decreases as the capacitance increases. Consequently, when distributed capacitance exists in a transformer, the transformer temperature rise due to iron loss is smaller than that in transformers without distributed capacitance. This indicates that the transformer temperature rise due to iron loss, which varies along with the distributed capacitance, needs not be taken into consideration in transformer thermal design even if the distributed capacitance increases in a high-voltage transformer.