Electrically Excited Research Articles

Analytical Calculation of the No-Load Magnetic Field of a Hybrid Excitation Generator

Hybrid excitation generators combine the advantages of electric excitation motors and permanent magnet generators. Focusing on a permanent magnet generator as the object of study, an auxiliary excitation winding is introduced for voltage regulation. The main magnetic field is established by the permanent magnet, and the auxiliary excitation winding provides the magnetic potential required to regulate the air-gap magnetic field. While improving the voltage regulation performance of permanent magnet generators, it also reduces the loss of excitation windings in electrically excited generators. Based on a hybrid excitation generator with dual excitation windings, in the following article, we present a hybrid excitation generator equivalent to a full permanent magnet motor with the minimum output voltage, and an accurate subdomain model of the full permanent magnet motor is established considering the influence of slot opening. By establishing a matrix, the distribution curve of air-gap magnetic density was solved and ultimately verified using finite element analysis. The results of the present study lay a solid foundation for solving the air-gap magnetic density distribution of various parts of the hybrid excitation generator and studying its performance in the future.

Iontolysis using an electrically excited solid source of aqueous copper ions compatible with bacterial gene quantification

Iontolysis was demonstrated as a feasible low-voltage and low-frequency technique for bacterial DNA extraction. This was achieved through mild electrical excitation (3 Vpp with a 0.5 VDC offset at 5 Hz sinusoidal signal) of submerged copper thin films serving as a solid source for releasing aqueous copper ions into the bacterial sample upon electrical stimulation. The technique achieved approximately 40 % of the lysing efficiency of bead beating after 5 min. The electrical power consumption per Escherichia coli K12 bacterial sample was approximately 25 mW, making it suitable for use with existing portable analyzers. Its compatibility with the existing intercalating fluorescent dye gene quantification technique was demonstrated with high linearity (R2 = 0.97). Notably, it suggested the minimal presence of interfering species that may have been generated from the iontolysis byproducts. This compatibility is essential for existing bacterial gene quantification techniques to leverage the low electrical power consumption, simplicity of design and manufacturing, and ease of storage and shipping of the proposed iontolysis.

High efficiency flux switching motor

Flux switching motor (FSM) with field excitation is permanent magnet free and attractive for many industrial and domestic applications. However, design with the conventional trapezoidal stator slot has low efficiency and always been a challenge in the state of the art. Further, the finite element analysis (FEA) method for the electromagnetic performance investigation is a powerful tool, but, it has high computational time, computational complexity and drive storage. To address the concern of low efficiency, in this paper, a new single phase 8slots–6poles electrically excited (EE) FSM design with the rectangular stator slot (RSS), salient rotor and non-overlapped windings for pedestal fan applications is been proposed. The proposed RSS EEFSM design is analyzed analytically and the analytical results are validated by FEA method. Finally, experimental test of the proposed EEFSM prototype is performed. The measured results are in a good agreement with the calculated results. Moreover, the proposed RSS EEFSM has higher efficiency as compared to the conventional design.

Research on Output Voltage Stability of Non-Contact Excitation Motor

In recent years, electric vehicles have developed rapidly. However, many electric cars are equipped with permanent magnet synchronous motors. Permanent magnet synchronous motors have several disadvantages: For example, permanent magnets tend to demagnetize at high temperatures. Electrically excited synchronous motors have several excellent properties. First, they are cheaper because the stator and rotor of the motor only need to be wound, which is more affordable than permanent magnets for speed regulation. When the armature current reaches the maximum value, the excitation current can also be adjusted for speed regulation, which makes the speed regulation more flexible. In the case of a short circuit, the corresponding direct-axis current is smaller than the quadrature-axis current, so the fault tolerance is better. Since the traditional electric excitation motor has brushes and slips rings, sparks will be generated during commutation. Therefore, a new excitation method is adopted to make non-contact motor excitation, and the motor operation is safer and more environmentally friendly. At the same time, to ensure that the output power of the non-contact electric excitation motor remains stable, a step-down circuit and power-type fast discrete terminal sliding mode control are added after the full-bridge rectifier circuit to make the excitation current and voltage output of the motor more stable. That is, the output power reaches a steady production. In this paper, an improved sliding mode control algorithm is used to stabilize the output voltage of the non-contact excitation motor, which can still ensure the stable output of the voltage when the equivalent load changes. It is confirmed that the non-contact excitation motor can be applied to various complex situations, and the proposed algorithm is simulated and experimentally verified to verify the accuracy of the proposed algorithm.

Torque Ripples Reduction and Performance Analysis of Electrically Excited Flux Switching Motor

Torque ripples cause acoustic noise, fluctuation in speed, vibration, and reduce lifetime of the motor. The double salient structure of Flux Switching Motor (FSM) has a high air-gap permeance variation that produces high torque ripples. This paper presents an analytical model to reduce air-gap permeance variation and torque ripples of the proposed octane modular stator 8slots-6poles single-phase Electrically Excited (EE) FSM. Furthermore, the rotor pole shaping technique is used to minimize the air-gap permeance variation and therefore, torque ripples of the proposed design are reduced. The electromagnetic performance of EEFSM is analyzed via the Finite Element Analysis (FEA) method. For the proposed design magnetic flux harmonics are reduced by 71% and back-EMF harmonics are suppressed by 48.5%. Torque ripples of the proposed EEFSM are reduced by 20%, cogging torque is diminished by 42.7% and average torque is enhanced by 5.8%. Finally, the prototype is fabricated and tested experimentally. Calculated values and experimental results are in good agreement and the difference is 3.5%-5%.

Air-Gap Flux Oriented Vector Control Based on Reduced-Order Flux Observer for EESM

Electrically excited synchronous motor (EESM) has the characteristics of high order, nonlinear and strong coupling, so it is difficult to be controlled. However, it has the advantages of adjustable power factor, high efficiency, and high precision torque control, so it is widely used in high-power applications. The accuracy of a flux observer influences the speed control system of EESM. Based on state observer in modern control theory and electrical excitation synchronous machine state equation, a reduced-order flux observer is designed. Using the first-order difference method and forward bilinear transformation method, the reduced-order flux observer is discrete, and the stability of the motor system is analyzed. The analysis shows that the stability of the system using the bilinear transformation method is better than that using the first order forward difference method. In motor operation, motor parameters will be affected by the factors of temperature, magnetic saturation, and motor frequency. In this paper, the influence of parameter variation on the motor system is studied by using the variation of the pole distribution. Finally, the speed regulation system using the reduced-order observer is simulated, which verifies the accuracy of the reduced-order flux observer observation.

Universal phase dynamics in VO 2 switches revealed by ultrafast operando diffraction

A transient metal Vanadium dioxide is known to have a coupled structural and electronic transition that can be accessed through light, thermal, or electrical excitation. Ultrafast optical studies of this insulator-to-metal transition indicate that it is mediated by the formation of a transient metallic phase that retains the structure of the original insulating phase. Sood et al. show that a similar sequence occurs when the material is electrically excited with a series of voltage pulses. Using ultrafast electron diffraction, the researchers monitored the structure of a vanadium dioxide sample after excitation and found evidence of a metastable metallic phase that appears during the transition. Science , abc0652, this issue p. 352

A transient metal

Oxide Electronics Vanadium dioxide is known to have a coupled structural and electronic transition that can be accessed through light, thermal, or electrical excitation. Ultrafast optical studies of this insulator-to-metal transition indicate that it is mediated by the formation of a transient metallic phase that retains the structure of the original insulating phase. Sood et al. show that a similar sequence occurs when the material is electrically excited with a series of voltage pulses. Using ultrafast electron diffraction, the researchers monitored the structure of a vanadium dioxide sample after excitation and found evidence of a metastable metallic phase that appears during the transition. Science , abc0652, this issue p. [352][1] [1]: /lookup/doi/10.1126/science.abc0652

Design and Optimization of a Hybrid Excitation System for Magnetically Driven Rotating DC Arc Plasma Generators

To eliminate the disadvantages of both the uncontrollability in the magnetic field of a permanent magnet excitation system and the high energy consumption of an electric excitation system in a traditional magnetically rotating arc plasma generator, a novel topology of a hybrid permanent magnet and electrically excited coil system is proposed. The proposed system will generate a large enough magnetic field to drive the arc rotation with a minimum consumption of materials and electric energy in the normal operation duty, and will guarantee a nearly zero magnetic field in the arc triggering stage. To optimize the hybrid excitation system, a comprehensive analysis and an optimization methodology; by combining finite element analysis, the moving the least squares approximation and an adaptive weighted particle swarm optimization, are proposed. Finally, a prototype hybrid excitation system is optimized with promising results in views of both saving a huge amount of electric power consumptions and ensuring a nearly zero magnetic field in the arc triggering.

Rotor Field Oriented Control of Resonant Wireless Electrically Excited Synchronous Motor

In order to solve the problems of wear and spark of the brush and slip ring in an electrically excited synchronous motor (EESM), based on the principle of magnetic resonance coupling wireless power transfer (MRC-WPT), a resonant wireless excitation system of EESM is designed. By modeling the EESM and analyzing the rotor field oriented control (RFOC) method, a control system of the resonant wireless EESM (RW-EESM) is established. Furthermore, the stator current distribution strategy is analyzed. Finally, a test of the RE-EESM prototype is carried out. The test results show that the motor can realize no-load stable operation, and the test speed is maintained at 85 r/min. The results show that the wireless excitation scheme of EESM is feasible, and the RFOC of RW-EESM motor is reasonable.

RESEARCH OF WIDEBAND HYDRO ACOUSTIC SYSTEM, CONTAINING TRANSDUCERS OF WAVEGUIDE TYPE

The results of experimental research of models of antennas hydroacoustic system (HAS), containing transducers of the waveguide type (TWT), which represent a coaxial set of identical water-filled piezocylinders, electrically excited by the principle of a traveling wave formation in the inner cavity of the TWT, are given. Possibilities of the TWT are analyzed when they are excited in accordance with the solution of the synthesis problem for the investigated HAS. The realization of such excitation is carried out by means of software-controlled multichannel blocks and allows providing a close to uniform amplitude-frequency characteristic of radiation and linear phase-frequency characteristic of radiation in a 3-octave frequency band. The possibility of radiation in this band of ultrashort pulses, tunable in frequency, as well as the formation of signals similar to the signals of cetaceans, is shown. The influence of the number of active piezocylinders of the TWT and the character of its electric excitation on the frequency and impulse response of the investigated HAS is considered. Directional properties of models of antennas HAS, including scanning and pulse operation modes, are considered. A comparative evaluation of the calculated and experimental data, as well as an evaluation of the efficiency of the TWT radiation, is given.

Effects of Design Parameters on Performance of Brushless Electrically Excited Synchronous Reluctance Generator

Permanent magnet synchronous generators, doubly fed induction generators, and traditional electrically excited synchronous generators are widely used for wind power applications, especially large offshore installations. In order to eliminate brushes and slip rings for improved reliability and maintenance-free operation, as well as to avoid costly permanent magnets, a novel brushless electrically excited synchronous reluctance generator having many outstanding advantages has been proposed in this paper. The fundamental operating principles, finite-element analysis design studies, and performance optimization aspects have been thoroughly investigated by simulations and experimentally under different loading conditions. The effects of different pole combinations and rotor dimensions on the magnetic coupling capacity of this machine have been specifically addressed and fully verified by offline testing of the 6/2 pole and 8/4 pole prototypes with magnetic barrier reluctance rotor and a new hybrid cage rotor offering superior performance.

Design and Analysis of a New Brushless Electrically Excited Claw-Pole Generator for Hybrid Electric Vehicle

This paper presents a new brushless electrically excited claw-pole generator (EECPG) for vehicle power generation. The proposed design uses a toroidal excitation coil to magnetize all the stator poles and then generate effective power by complementary saliency effect of dual rotors. One salient advantage of this new design is its good excitation ability with minimized excitation copper loss as well as improved energy conversion efficiency. Meanwhile, the brush and slip rings are eliminated compared to the conventional rotor-EECPG. The generator structure is introduced, with its operating principle illustrated by 3-D finite-element predicated flux distribution. Rotor configurations using interlaced and non-interlaced types are both elaborated in terms of back electromotive force harmonic distribution and cogging effect. Load characteristic is predicted by the field-circuit coupled analysis, which proves the proposed brushless claw-pole generator could serve as a high-efficiency cost-effective candidate for vehicle power generation.

Comparison of Mechanically and Electrically Excited Vibration Frequency Responses of a Small Distribution Transformer

A clear understanding of the vibration characteristics of power transformers is necessary to detect electrical and mechanical faults in a transformer using vibration-based monitoring strategies. This paper focuses on the measurement and analysis of the vibration frequency-response functions (FRF) of a 10-kVA distribution transformer due to mechanical and electrical excitations. The modal characteristics of the transformer are extracted from the FRFs, and can be used for reference models for future transformer fault detection. The effect of the magnetizing hysteresis in the transformer core on the measured FRF is also examined.

Surface plasmon polariton beams from an electrically excited plasmonic crystal.

Surface plasmon polariton (SPP) beams with an in-plane angular spread of 8° are produced by electrically exciting a 2D plasmonic crystal using a scanning tunneling microscope (STM). The plasmonic crystal consists of a gold nanoparticle (NP) array on a thin gold film on a glass substrate and it is the inelastic tunnel electrons (IET) from the STM that provide a localized and spectrally broadband SPP source. Surface waves on the gold film are shown to be essential for the coupling of the local, electrical excitation to the extended NP array, thus leading to the creation of SPP beams. A simple model of the scattering of SPPs by the array is used to explain the origin and direction of the generated SPP beams under certain conditions. In order to take into account the broadband spectrum of the source, calculations realized using finite-difference time-domain (FDTD) methods are obtained, showing that bandgaps for SPP propagation exist for certain wavelengths and indicating how changing the pitch of the NP array may enhance the SPP beaming effect.

Performance Investigation of a Brushless Synchronous Machine With Additional Harmonic Field Windings

This paper describes a brushless electrically excited synchronous machine with a distinctive rotor structure and additional harmonic field windings. Spatially distributed third harmonic magnetic fields will be created in the air gap by feeding the stator harmonic windings of a dc current. These harmonic MMFs will generate an induced voltage in the additional rotor harmonic coils, which can supply the field winding with a dc current after rectification. Based on this operation principle, distributions of harmonic windings and the stator harmonic magnetic fields are analyzed. The relationship between harmonic EMFs and rotor harmonic winding turns are studied. Mutual interference between the different magnetic fields and windings in the machine is discussed. The harmonic excitation fields and the air gap flux densities are then calculated by employing finite element methods, and the regulating characteristics of no-load EMF are analyzed and power losses of machine are discussed. Experimental results of one 1.0-kW prototype machine agree well with the theoretical analysis and finite element calculations, which helps to evaluate this type of synchronous machines having brushless electrical excitation.

Simulation and Experimental Analysis of a Brushless Electrically Excited Synchronous Machine With a Hybrid Rotor

Electrically excited synchronous machines with brushes and slip rings are popular but hardly used in inflammable and explosive environments. This paper proposes a new brushless electrically excited synchronous motor with a hybrid rotor. It eliminates the use of brushes and slip rings so as to improve the reliability and cost-effectiveness of the traction drive. The proposed motor is characterized with two sets of stator windings with two different pole numbers to provide excitation and drive torque independently. This paper introduces the structure and operating principle of the machine, followed by the analysis of the air-gap magnetic field using the finite-element method. The influence of the excitation winding’s pole number on the coupling capability is studied and the operating characteristics of the machine are simulated. These are further examined by the experimental tests on a 16 kW prototype motor. The machine is proved to have good static and dynamic performance, which meets the stringent requirements for traction applications.

Optical and Electrical Excitation of Hybrid Guided Modes in an Organic Nanofiber–Gold Film System

We report on the optical and electrical excitation of the modes of a “hybrid” waveguide consisting of a single organic nanofiber on a thin gold film. In the first set of experiments, light is used to excite the photoluminescence of an organic nanofiber on a thin gold film and the resulting emission is analyzed using Fourier-space leakage radiation microscopy. Two guided modes and the dispersion relations of this hybrid waveguide are thus determined. From numerical calculations, both a fundamental and excited mode of mixed photonic–plasmonic character are identified. In a second experiment, a local electrical nanosource of surface plasmon polaritons (SPPs) is coupled to the hybrid waveguide. The SPP nanosource consists of the inelastic electron tunnel current between the tip of a scanning tunneling microscope (STM) and the gold film. We show that the electrically excited SPPs couple to the fundamental mode and that the coupling efficiency is highest when the SPP nanosource is aligned with the nanofiber axi...

Investigation on Operational Envelops and Efficiency Maps of Electrically Excited Machines for Electrical Vehicle Applications

In this paper, the operational envelops and efficiency maps of an electrically excited (EE) machine with/without employing flux weakening control via armature current and/or with/without the field excitation regulating are obtained and comprehensively compared for electric vehicle applications. It shows that even in EE machines, only using the field excitation regulating but without the flux weakening armature current control, the maximum power at high speed is not constant but inversely proportional to the machine speed. Only by employing the flux weakening armature current control, the maximum constant power operation at high-speed region can be achieved while the operational high-speed region can be greatly extended. The maximum efficiency in this extended high-speed region can be achieved when both the field excitation and flux weakening ${d}$ -axis armature current change proportionally. The main benefit of the field excitation regulating is that the efficiency in low-torque region can be significantly improved. All the analyses are validated analytically.

Simplified Analytical Optimization and Comparison of Torque Densities Between Electrically Excited and Permanent-Magnet Machines

This paper presents the simplified analytical optimization and comparison between electrically excited (EE) and permanent-magnet (PM) machines in terms of torque per volume T/V and torque per weight T/G for low-speed applications when their copper loss and overall size are the same. Analytical torque models for both machines are individually developed and optimized to obtain the optimal flux density ratio, split ratio, and maximum torque densities. Furthermore, the variation of optima with the number of poles and machine size is also investigated. The analytical analyses are validated by both finite-element analyses and experiments. It is concluded that torque densities of PM machines can be more than √2 times higher than those of EE machines. For EE machines, there is an optimal pole number to maximize torque densities, and large volume applications are preferred. In actual applications, EE machines are more likely to compromise the torque density to meet the thermal constraints. It also shows that the optimal T/G designs have significantly higher split ratio and are more cost- and weight-effective than the optimal T/V designs.