Magnetic Flux Modulation Research Articles

Modified Efficient Energy Conversion System Based on PMSG with Magnetic Flux Modulation

The article presents the solution of a power rectifier system dedicated to cooperating with an electric generator based on a special synchronous generator, which can be used in wind or water energy systems. In this generator, a pair of three-phase windings in a stator is utilized. One of the windings is connected in a star, and the second one is connected in a delta configuration. Two six-pulse uncontrolled (diode) rectifiers are included at the outputs of the windings. The rectifiers are coupled by a pulse transformer. The primary windings of this transformer are supplied by a power-electronics current source called a current modulator. With the help of this current modulator, the quasi-sinusoidal magnetomotive force (mmf) in the stator of the machine can be obtained. Additionally, to improve the efficiency of the described system, the low-power transistor rectifier, which is connected to the DC bus of the current modulator, has been used. With the help of this converter, it is possible to control and stabilize the voltage level in a DC circuit. It works, in this case, in inverter mode. The principle of working and elaborated control methods of the current modulator and the additional rectifier are presented. Selected results of simulation and experimental tests are also presented.

Tunable caging of excitation in decorated Lieb-ladder geometry with long-range connectivity

Controlled Aharonov–Bohm caging of wave train is reported in a quasi-one-dimensional version of Lieb geometry with next-nearest-neighbor hopping integral within the tight-binding framework. This longer-wavelength fluctuation is considered by incorporating periodic, quasi-periodic or fractal kind of geometry inside the skeleton of the original network. This invites exotic eigenspectrum displaying a distribution of flat band states. Also a subtle modulation of external magnetic flux leads to a comprehensive control over those non-resonant modes. Real space renormalization group method provides us an exact analytical prescription for the study of such tunable imprisonment of excitation. The non-trivial tunability of external agent is important as well as challenging in the context of experimental perspective.

Position Estimation Method for Switched Reluctance Motors Based on Magnetic Flux Modulation

There are different position sensors to drive electric machines such as encoders, opto-interrupters, and resolvers to provide information about the position of the rotary part. However, these sensors affect the reliability of the propulsion system and increase the drive system cost considerably. To overcome this problem, this article proposed a novel method for sensing the rotor position of a switched reluctance motor (SRM) used in a hybrid electric vehicle (HEV). In this method, a low-amplitude high-frequency (HF) voltage waveform is injected into the three sets of toroidally wounded HF windings in the back-iron of the machine to modulate the position information in the amplitude of magnetic flux. After filtering the induced voltage in signal windings and processing the output signals, the envelopes of signals are demodulated for further investigation. Voltage Derivative is the method that is proposed in this article. In the Derivative Voltage method, the derivative of the extracted envelope is calculated in each step with regard to the time and the obtained value is compared to the lookup table (LUT) to compute the possible position of the rotor. The proposed method is cheap and maintains the robustness of the machine at the same time. The presented sensing method is studied on the SRM with 24 stator poles and 16 rotor poles. Finite-element analysis (FEA) is used to simulate and validate the efficacy of the proposed sensing technique.

A gate- and flux-controlled supercurrent diode effect

Non-reciprocal charge transport in supercurrent diodes (SDs) has polarized growing interest in the last few years for their potential applications in superconducting electronics (SCE). So far, SD effects have been reported in complex hybrid superconductor/semiconductor structures or metallic systems subject to moderate magnetic fields, thus showing limited potentiality for practical applications in SCE. Here, we report the design and realization of a monolithic device that shows a valuable SD effect by exploiting a Dayem bridge-based superconducting quantum interference device. Our structure allows reaching rectification efficiencies (η) up to ∼6%. Moreover, the absolute value and the polarity of η can be selected on demand by the modulation of an external magnetic flux or by a gate voltage, thereby guaranteeing high versatility and improved switching speed. Furthermore, our SD operates in a wide range of temperatures up to about 70% of the superconducting critical temperature of the titanium film composing the interferometer. Our SD effect can find extended applications in SCE by operating in synergy with widespread superconducting technologies such as nanocryotrons, rapid single flux quanta, and memories.

The basic specifications of magnetic flux modulation gear

The basic specifications of magnetic flux modulation gear

Research on Slot-pole Combination in High-power Direct-drive PM Vernier Generator for Fractional Frequency Transmission System

Offshore wind energy is an important part of clean energy, and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals. The combination of the fractional frequency transmission system (FFTS) and the direct-drive wind turbine generator will be beneficial to the development of the offshore wind power industry. The use of fractional frequency in FFTS is beneficial to the transmission of electrical energy, but it will also lead to an increase in the volume and weight of the generator, which is unfavorable for wind power generation. Improving the torque density of the generator can effectively reduce the volume of the generators. The vernier permanent magnet machine (VPM) operates on the magnetic flux modulation principle and has the merits of high torque density. In the field of electric machines, the vernier machine based on the principle of magnetic flux modulation has been proved its feasibility to reduce the volume and weight. However, in the field of low-speed direct-drive machines for high-power fractional frequency power generation, there are still few related researches. Therefore, this paper studies the application of magnetic flux modulation in fractional frequency and high-power direct-drive wind turbine generators, mainly analyzes the influence of different pole ratios and different pole pairs on the generator, and draws some conclusions to provide reference for the design of wind turbine generators.

Optimization of a hybrid electromagnetic system with magnetic modulation

The paper presents optimization of a newly developed hybrid electromagnetic system with magnetic flux modulation, for which patent application has been submitted. The efficiency of the system has been taken as objective function. The optimization factors include both geometrical and electrical parameters. Finite element method and three-dimensional coupled time-dependent electromagnetic field-electrical circuit analysis has been used for the solution of the forward problem. Response surface methodology and sequential linear programming are employed for the optimization.

A Mesh Design Technique for Double Stator Linear PM Vernier Machine Based on Equivalent Magnetic Network Modeling

Linear permanent magnet Vernier machines (LPMVMs) is an attractive solution for stroke and direct-drive applications. Several LPMVM topologies have been presented for different applications that operate based on magnetic flux modulation. LPMVMs have some advantages including high force, and torque density at low speeds. This paper introduces a double-excited linear Vernier machine for wave energy conversion. To model the machine, finite element analysis and nonlinear equivalent network model are used. To improve the accuracy of the model and compact the network, a new meshing method is proposed. For better continuity in the output waveforms of the machine, special positioning is utilized. The end-effect is modeled using two separate networks. Finally, the modeling and simulation results are compared with each other and validated experimentally.

Precise Strong Magnet Measurement Method Based on Magnetic Flux Modulation Principle

Superconducting magnets with stable and strong magnetic fields play a pivotal role in fields such as biology, medical science, and physics. Given the difficult measurement conditions and low measurement accuracy of the strong magnetic field, a measurement method based on magnetic flux modulation is proposed in this paper. Additionally, a high-stability coil-driving device is established. A circuit for coil speed acquisition and measurement is developed. The effective values of induced electromotive forces corresponding to the measured strong magnetic field are obtained, following the de-noising principle of the lock-in amplifier. Particularly, a traceable transmission standard is formed when the measurement coil is calibrated by the national standard magnetic field. The experimental system results demonstrated that the uncertainty of the proposed method reaches the order of E-4 for the measurement of magnetic induction intensity below 7T. This significantly contributes to the measurement of superconducting strong magnetic fields.

Dynamic behaviours of double-ended tuning fork based comb-driven microelectromechanical resonators for modulating magnetic flux synchronously

Microelectromechanical system (MEMS) resonators have been widely used in the magneto-resistive (MR) sensor for modulating the magnetic flux to enhance the detection limit. However, the manufacturing tolerances in MEMS fabrication processes make it challenging to fabricate the identical resonators with the same vibration frequency, which greatly decreases the detection limit of the MR sensor. To synchronize the MEMS resonators and improve the performance of the MR sensor, the double-ended tuning fork (DETF) based comb-driven MEMS resonators is proposed in this paper, making the system operate at the out-of-phase mode to complete the synchronization. The dynamic behaviour of the resonators is investigated through theoretical analysis, numerical solution based on MATLAB code and Simulink, and experimental verification. The results show that the transverse capacitances in the comb will significantly affect the resonance frequency due to the second-order electrostatic spring constant. It is the first time to observe the phenomenon that the resonant frequency increases with the increase of the bias, and it can also decrease with increasing the bias through adjusting the initial space between the fixed finger and the moving mass, they are different from the model about spring softening and spring hardening. Besides, the proposed DETF based comb-driven resonators can suppress the in-phase and out-of-phase mode through adjusting the driving and sensing ports, and sensing method, meanwhile make the magnetic flux modulation fully synchronized, and maximize the modulation efficiency, and minimize the detection limit. These characteristics are appropriate for the MR sensor, even other devices that need to adjust the resonance frequency and vibration amplitude. Furthermore, the model and the design can also be extended to characteristic the single end tuning fork based MEMS resonator and other MEMS-based MR sensors.

Design Optimization of a HTS-Modulated PM Wind Generator

The flux-modulated machine based on air-gap magnetic flux modulation theory has become a focus in low speed and high torque density applications. In this paper, the optimal design of a large scale flux modulation (FM) permanent magnet (PM) generator with high temperature superconducting (HTS) bucks for wind energy conversion systems is presented. Firstly, the working performances of the generator with and without HTS bucks sandwiched between iron segments are analyzed and compared through finite element analyses (FEA). The FM effect enhancement by employing the HTS bucks is proved through the comparisons. Secondly, the sensitivities of the generator structural parameters on the back electromotive force (EMF) and the cogging torque amplitude are analyzed by Taguchi method to decide the optimization variables and their variation ranges. Thirdly, the structural parameters determined by the sensitivity analyses are optimized through the coupling of genetic algorithm (GA) and FEA to maximum the generator output power capacity. The calculation burden during optimization is reduced with a reduction on the optimization variable number through the Taguchi method based sensitivity analyses. Finally, the electromagnetic characteristics of the FMPM generator with optimized structural sizes are numerically investigated.

Influence of the shape of the input pulses on the characteristics of hybrid electromagnetic system with magnetic flux modulation

Introduction. Nowadays, the accelerated development of materials and technologies and the finding of new ones is a prerequisite for the improvement of well-known electromagnetic constructions used in various devices, as well as for the development of new ones. New construction of hybrid electromagnetic system with magnetic flux modulation (HEMSMM) is studied. The construction is composed of: ferromagnetic frame with air gaps, input and output coils and permanent magnets. Two input coils connected to the pulsed power supply are used to change the path of the generated by the permanent magnets constant magnetic flux. Input pulses with different shapes are applied to the input coils and signals in the output coils are obtained and compared. The main purpose of the work is to find the shape of the input pulses which leads to higher output power in comparison with the other shapes. Methods. Finite element method and COMSOL software is used for computer modelling of the proposed construction, where coupled electromagnetic field – electric circuit analysis is carried out. Results. A mathematical and numerical 3D model of new HEMSMM construction is realised and studied. The model allows to calculate and compare power efficiency of the studied device, when input pulses with different shapes are applied. Practical value. The developed computer model enables the study of the HEMSMM and other electromagnetic devices at different operating modes. It can be further improved and used in the search for optimal parameters of a particular electromagnetic device.

Core-Loss Analysis of Linear Magnetic Gears Using the Analytical Method

In this study, analysis of core-loss occurring in the magnetic flux modulation core of a linear magnetic gear and the core of each mover is presented, using an analytical method. Losses in electric machines were generally calculated and analyzed using the finite element method (FEM). However, in the case of core-loss, the exact loss value could not be calculated using FEM data. Therefore, we considered the harmonic component of the air-gap magnetic flux density waveform with the modified Steinmetz equation, and performed a more accurate core-loss analysis with magnetic behavior analysis. Thus, we performed a calculated core-loss characteristic comparison with the FEM and the modified Steinmetz equation.

A High Torque Density Claw-Pole Permanent-Magnets Vernier Machine

Permanent magnets vernier (PMV) machine is gaining more and more attention due to its high torque density contributed by multi-orders working harmonics, especially low-pole-pair numbers harmonics. Spoke-array PM machine seems to be a good way to increase the machine working harmonics. But the flux barrier effect is revealed and it explains why the advantages of the spoke-array PMV (SAPMV) machine are not fully used. Thus, its low-pole-pair numbers harmonics could be further enhanced. In this article, a novel structure&#x2014;claw-pole PMV (CPPMV) machine&#x2014;is first proposed and its working principle is investigated. Then, the CPPMV machine is compared with the surface-mounted PMV machine, the SAPMV machine, and the SAPMV machine with alternate flux bridges in terms of their electromagnetic performances using equivalent circuit analysis and FEM. The result shows that claw-pole structure can enhance the magnetic flux modulation effects, which increases the machine torque density. At last, a CPPMV machine prototype is manufactured and tested. Experimental results indicate that it reaches a torque density of 30.5 kNm/<inline-formula> <tex-math notation="LaTeX">$\text{m}^{3}$ </tex-math></inline-formula> and a power factor of 0.84 underrated conditions.

Уменьшение магнитных потоков рассеяния в линейных генераторах Вернье с помощью высокотемпературных сверхпроводящих элементов

The article presents the results of studies aimed at improving the power performance indicators of linear electric generators for wave power plants by reducing the flux leakages using high-temperature superconducting (HTS) inserts placed in between the teeth. The generator design involving application of the Vernier principle for magnetic flux modulation with a translator in the form of a hollow cylinder is considered. Generators of this type are used in float wave power plants driven directly by a reciprocating float, which transmits large forces at a low motion speed. The calculations were carried out using the HTS properties modeling procedure based on representing the currents induced in a superconductor in the form of magnetic moments of these currents, which made it possible to simplify the analysis of the electromagnetic field in the generator without significant additional errors. As a result, the characteristics of the electromagnetic force longitudinal components and phase winding flux linkages versus the translator displacement have been obtained. The use of HTS inserts and a distributed winding in the stator made it possible to reduce the electromagnetic leakage losses and increase the interaction force between the stator and translator. However, since the additional outlays for the cooling system and thermal insulation of the HTS elements are commensurable with the generator cost, the obtained results on improving the power performance parameters do not allow an unambiguous statement to be made about the effectiveness of the considered technical solutions.

Analytical Calculation of Surface-Inset PM In-Wheel Motors and Reduction of Torque Ripple

Accurate calculation of magnetic field distribution is a prerequisite for motor design and optimization. This article develops an analytical subdomain model of external rotor in-wheel motor with surface-inset magnets (ERIWMSIMs). Besides, to weaken its torque ripple, an improved topology by integrating magnetic flux modulation slots (MFMSs) into tooth tips is proposed. First, the entire field problem is divided into five subdomains, viz., magnet rotor slots, air gap, stator slots, stator slot openings, and MFMSs. Then, this study solves Laplace's or Poisson's equation of magnetic vector potential in each subdomain according to the type of excitation source and use the boundary conditions of adjacent subdomains to determine the magnetic field solution. Consequently, the electromagnetic performances such as air gap flux density, back electromotive (EMF), cogging torque, and on-load output torque are accurately predicted. The analytical results are shown in line with those obtained from finite-element analysis (FEA) and experimental results. Furthermore, the influence of MFMS parameters on the torque is further investigated. When double MFMSs are integrated into each tooth tip, the depth of the MFMS is 0.7 mm, and the width is 1.05 times the slot opening; the results demonstrate that the torque ripple can be essentially weakened compared with other topologies.

Magnetic flux modulation with electric controlled permeability for magnetoresistive sensor

Owing to the attractive advantages of the simple preparation process, convenient frequency adjustment, and stable mechanical structure, magnetic flux modulation with electric controlled permeability exhibits a better performance in the reduction of 1/f noise for magnetoresistive (MR) sensors than other schemes of magnetic flux modulation. However, the magnetic flux electric modulation (MFEM) has not been experimentally verified. In this work, a prototype of the MFEM structure was established by preparing an FeGaB film on a Pb(Mg1/3Nb2/3)0.7O3–PbTi0.3O3 substrate, and the modulation structure was integrated into an MR sensor. A test system was built to evaluate the modulation efficiency of the MFEM structure, and the results showed that the modulation efficiency reached 9.8% with an applied electric field of 2 kV/cm at a frequency of 10 010 Hz. Meanwhile, experiments were carried out to study the effects of driving electric fields’ amplitude and frequency on modulation efficiency, and it was revealed that the modulation efficiency could be further improved by increasing the amplitude of driving voltage and reducing the thickness of the ferroelectric layer.

Anchor loss optimization for magnetic flux modulation structure of magnetoresistive sensor

Piezoelectric driven magnetic flux modulation is an effective method to suppress 1/f noise of magnetoresistive sensor, and obtaining a modulation structure with high quality factor (Q factor) is of great significance in improving the modulation performance. In this paper, influence of anchor positions on the Q factor was investigated with simulation and experiment methods. First, Q factor dependent on damping of each material was analyzed, and the upper limit for studying the anchor loss was given. The displacement and stress distributions of the ceramic substrate were also simulated, so as to indirectly guide the selection of anchor locations. Then a fixture was applied to investigate the Q factor under different clamped positions, and the results shows that the clamping condition does have a great effect on the Q factor, and the smaller the stress and displacement at the support are, the larger the Q factor is. Accordingly, the modulation structure was fixed to the package base in a diagonally fixed manner or short side centers fixed manner, and the maximal Q factor reached 920, which is much higher than that under other fixed manners.

Effect of magnetic flux modulation on noise characteristics of tunnel magnetoresistive sensors

Magnetic flux modulation technology aims to shift the low frequency or dc magnetic field to a higher frequency band and avoid the influence of 1/f noise in a magnetoresistance sensor. Despite decades of development, there are relatively few studies devoted to the impact of this technology on the noise characteristic of a magnetoresistance sensor. In this paper, we fabricated a tunnel magnetoresistance sensor integrated with a magnetic flux modulation structure and explored the noise characteristics under modulation. It was found that the noise at the modulation frequency will increase significantly when the external magnetic field is large, and this is caused by the ac magnetic field after modulation. The maximum value of noise at the modulation frequency is up to 12 μV/√Hz under modulation, which is 63 times higher than that without modulation. Obviously, this result indicates that magnetic flux modulation technology may be ineffective in reducing 1/f noise. Fortunately, it was also observed that when the external magnetic field is small, the noise increase is not obvious. Based on this, we proposed a magnetic field tracking compensation method to keep the measured magnetic field constantly close to zero and prevent the deterioration of noise, no matter how the external magnetic field changes. A compensating coil was designed and manufactured to generate the compensating magnetic field. The test results show that the increase in noise under modulation can be well suppressed with magnetic field tracking compensation.

High Efficiency Magnetic Flux Modulation Structure for Magnetoresistance Sensor

After decades of development, low modulation efficiency is still the bottleneck of magnetic flux modulation technology for 1/f noise reduction of magnetoresistance sensors. To address this difficulty, a simulation on modulation efficiency improvement was conducted. It was interpreted that the major factors affecting the modulation efficiency were the initial position of the modulation film and its minimum distance to the magnetic sensitive element during the vibrating process. Moreover, size optimization and permeability increment of the modulation film also contribute to the increase in modulation efficiency. Given these simulation results, a piezoelectric actuated magnetic flux modulation structure with amplitude feedback function was proposed and then fabricated using micro-electromechanical system technology, primarily considering the initial height control, the expected amplitude control as well as the material properties of the modulation film. Test results of the sensor prototype suggested that the modulation efficiency is up to 68.7%, much higher than the currently reported value of 18.8%.