Yoke Width Research Articles

Analysis and Design of a Novel Doubly SalientPMMotor Based on Parallel Path Magnetic Technology

AbstractIn this paper, a novel doubly salient PM motor based on parallel path magnetic technology (PPMT) is presented. PPMT is an advanced magnetic control technology, which can be applied to linear and rotary actuators. First, the fundamental principle of the PPMT prototype is elaborated, and then a comprehensive research and analysis of PPMT motor is carried out, with particular emphasis on machine topology, operation principle and electromagnetic performance. The equivalent no‐load PM magnetic circuit model is established and equations for calculating the main PM flux are derived. Besides, a dual‐stator 6‐pole PPMT motor prototype has been developed to valid the analysis. According to the similarity of topology and operation principle, comparison between the FSPM machine and PPMT machine is conducted, which leads to the conclusion that the PPMT motor has lower cogging torque, lower torque ripple and better sine back EMF waveform, the PPMT motor is more suitable for servo applications compared to FSPM motor. Finally, to improve the power density of PPMT motor, FE parametric modeling method for designing the three coupled stator parameters, which are the PM width, the stator yoke width and the second airgap length is given out. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Study of Vernier permanent magnet machine with the dual rotor, toroidal winding and ferrite magnet on both sides of stator and rotor

A dual-rotor permanent magnet Vernier machine (DRPMVM) with permanent magnets (PMs) on both sides of the rotor and stator is proposed and studied here. The configuration and working principle are provided, then the expression of coil-side voltage is obtained based on the rotating harmonics of the air gap flux density. The effects of the rotor slot number on the amplitudes and phase differences of the voltage components are explored, and suitable combinations of the stator and rotor slot numbers are selected. The impact of the rotor and stator PMs on the voltage is also compared. Different coil connection methods are adopted for the DRPMVM with 12-stator slot and 10-rotor slot, and the back electromotive force, d- and q-axes inductances, and torque-speed characteristics are compared. Using the finite element method, the effect of the main parameters, including slot and yoke width on the average torque and torque ripple are then studied. Finally, a prototype machine is produced and tested to verify the conclusions.

Magnetizing characteristic evaluation of REBCO bulk in PFM using different yokes

A REBCO bulk magnet is able to generate a several-tesla-class magnetic field by a compact system with low power consumption. Pulsed field magnetization (PFM), which is one of major magnetization method, has the advantage that the bulk is activated using a conventional equipment in a few seconds, and, therefore, it is suitable for practical use. However, a trapped field is lower than the maximum performance of material. To increase the field, improvement of magnetization method and modification of exciting equipment are considered. We aim to improve the trapped field by changing the exciting system simply and inexpensively. In the bulk magnet system, soft-iron yokes are generally used to extend the pulse width. This paper evaluated magnetizing characteristic quantitatively. A single pulsed field was applied to a new GdBCO bulk using ϕ64-mm and ϕ80-mm soft-iron yokes. The pulse width of ϕ80-mm yoke was about 35% longer than that of ϕ64-mm yoke. When comparing the trapped flux density and total magnetic flux, these values of ϕ80-mm yoke were higher than those of ϕ64-mm yoke. Also, the temperature rise of ϕ80-mm yoke was decreased by approximately 5% as compared with ϕ64-mm yoke, implying that the same effect as the long-pulse method was achieved.

Modeling and Design of a 3-DOF Magnetic Bearing With Toroidal Radial Control Coils

This paper presents a 3 degrees of freedom magnetic bearing (3-DOF MB) with toroidal radial control coils. By using the toroidal coils, the proposed structure reduces the copper loss but increases the copper usage of the radial control coils. The variation is mainly related to the stator length, pole width, and yoke width. The overall structure is symmetrical about the radial stator in the axial direction, and the cross-coupling effect between the radial and axial directions can be restrained. A magnetic circuit (MC) model is built to design the structure parameters. The force characteristics calculated by the MC model and 3-D finite-element method (FEM) verify the rationality of the design. The influence of the control currents and displacements of other directions on the force characteristics are analyzed by the 3-D FEM, and the weak cross-coupling effect of the proposed 3-DOF MB is confirmed. The accuracy of the MC model and 3-D FEM is validated by the prototype experiments.

Performance Analysis of Novel Single-Phase Parallel Hybrid-Excited Flux-Switching Machine

To obtain magnetic field regulation capacity and reduce copper loss in the field winding, a single-phase parallel hybrid-excited flux-switching machine (PHEFSM) is investigated in this paper. Because the permanent magnet with tangential magnetization is fixed at the slot opening of the field winding slot, the yoke width of the field winding slot determines the magnetic field regulation capacity, and the saturation condition varies significantly with the field current. To accurately calculate the performance of PHEFSM, a nonlinear magnetic equivalent circuit model that considers the iron saturation is derived, and it is verified by the finite-element method. A composite rotor with two kinds of rotor core laminations is adopted to obtain self-starting capability. Two prototype machines with a classical rotor and a composite rotor are produced and tested to verify the conclusions.

Optimal Design of Permanent Magnet Linear Generator and Its Application in a Wave Energy Conversion System

The emerging global wave energy industry has great potential to contribute to the world’s energy needs. However, one of the key challenges in designing a wave energy converter (WEC) is the wave energy generator. Thus, this paper focuses on the optimal design of a cylindrical permanent magnet linear generator (CPMLG), which is used for the wave energy conversion system. To reduce the end effect and enhance the magnetic field performance of the CPMLG, the level-set method is applied to the design of the topology and size for the generator. In the paper, the objective air gap magnetic field is given by the mathematical analysis method and appropriate measuring points are predetermined. The measuring points can fully reflect the distribution characteristics of the air gap magnetic field. Then, topology evolution on the permanent magnet (PM) and yoke based on the level-set method are performed. The level set function corresponding to the initial shape of the PM is constructed. The algorithm is programmed and computed iteratively using the discrete time and space variables. Finally, the performances of the CPMLG with the updated PM and width of yoke are analyzed by ANSYS Maxwell. Results show that the magnetic field distortion and the unbalance of three-phase electromotive force (EMF) of the CPMLG is reduced by the optimization of the level-set method. It has also been verified that the designed CPMLG with the level-set method could be used for WEC at different wave conditions.

Stator Shape Optimization for Electrical Motor Torque Density Improvement

The shape optimization of the stator and the rotor is important for electrical motor design. Among many motor design parameters, the stator tooth and yoke width are a few of the determinants of noload back-EMF and load torque. In this study, we proposed an equivalent magnetic circuit of motor stator for efficient stator tooth and yoke width shape optimization. Using the proposed equivalent magnetic circuit, we found the optimal tooth and yoke width for minimal magnetic resistance. To verify if load torque is truly maximized for the optimal tooth and yoke width indicated by the proposed method, we performed finite element analysis (FEA) to calculate load torque for different tooth and yoke widths. From the study, we confirmed reliability and usability of the proposed equivalent magnetic circuit.

Efficiency Improvement and Thermal Analysis of a Totally Enclosed Self-Cooling Doubly Salient Generator With Optimized Stator Yoke

In this paper, first, the distribution of electromagnetic loss of the proposed doubly salient electromagnetic generator (DSEG) with the variation of defined stator yoke width coefficient is analyzed. The design of stator yoke for the proposed DSEG is of great significance to the power density and output efficiency improvement due to the introduction of field winding. By building a 3-D thermal finite element model based on the optimized dimensions and calculated electromagnetic loss, thermal performance of the proposed DSEG is predicted to ensure the maximum temperature rise in the safe range. The impact of current density on thermal performance is studied as well. Finally, a totally enclosed self-cooling prototype DSEG has been developed and tested. Experimental results confirm the validity of the proposed DSEG with optimized stator yoke for a stand-alone power system application.

Micromagnetic Model Analysis of Planar Type Recording Write Heads for High Transfer-Rate Recording

Planar type recording write heads were investigated using a micromagnetic analysis targeting a transfer-rate of 5 GHz. Six different planar head structures with various yoke widths, yoke heights, and coil locations were modeled. Six different conventional single-pole-type (SPT) write heads were also used for comparison. The material characteristics including the exchange constant, anisotropy energy, and Gilbert damping factor were also varied. It was found that the planar heads had a faster high-frequency response, a larger recording field, and a smaller ATE field. In the planar head, the most dominant factor for high transfer-rate recording was the coil location relative to the main pole tip and the return yoke height, while the yoke width was less important. Because the multi-turn coil can be realized with a wide yoke, it is advantageous in the planar head. With regard to the material characteristics, a small Gilbert damping factor was the most effective, while the other material characteristics did not yield significant differences.

Magnetic design and manufacture of elliptical undulators HU256

Three elliptical undulators HU256 (period 256 mm) of electromagnetic type were produced, tested and magnetically measured by the Budker Institute of Nuclear Physics (Russia) for Synchrotron SOLEIL (France). The undulators have a new design of a Bx and Bz closed structure for insertion vacuum chamber. The magnetic calculations of the individual dipoles and undulator structures were executed by means of Mermaid 3D Code. The expected magnetic parameters for all manufactured dipoles were fulfilled on basis of these model dependences from the mechanical characteristics (pole gap, yoke width, and coil position). The estimated 1st integral of all dipoles had been used in an optimal arrangement of the dipoles in undulators (sorting). Owing to the realized sorting, the 1st integral of the magnetic field and phase error of the assembled undulators had been decreased in comparison with the statistic estimations. The special Hall probes systems for the magnetic measurements of the undulators HU256 were designed and manufactured by the BINP. All three HU256 undulators were magnetically measured at the BINP and re-measured at the SOLEIL after transportation. The results of magnetic measurements and model estimates are compared and analyzed.

Effect of Pole-Tip Geometry on the Flux Rise Time of Write Heads

With magnetic recording data transfer rates now in the gigabit-per-second regime, understanding and controlling all of the major write transducer characteristics governing magnetic flux rise time has become imperative. In this paper, we study dependence of the flux rise time on the front-end pole-tip geometry. We examined a set of recording heads differing only in pole-tip shape; the yoke length and width, number of coil turns, and pitch are the same for all designs. We measured the flux rise time by laser-based time-resolved scanning Kerr microscopy and observed that the front-end pole-tip geometry has a strong effect on flux rise time.

Inspection of stator cores in large machines with a low yoke induction method-measurement and analysis of interlamination short-circuits

Interlamination short-circuits can cause major damage to electrical machines. Especially endangered are large turbomachines with high yoke width and correspondingly high interlamination voltages. These generate during operation, at certain interlamination short-circuit contact resistance's, high short-circuit currents and lead in the worst case to "core melting." There is a need to develop a safe measuring method, which enables on one hand all interlamination short-circuits to be registered, and on the other hand a quantitative assessment of the danger of the interlamination short-circuits for the machine. For nearly 20 years a measuring method with lower yoke induction has been used without disadvantages of the high induction method. By this method an interlamination short-circuit is detected with a measuring coil. The signal has been interpreted in terms of current. With this interpretation of the measuring signal it is not possible to take a meaningful consistent quantitative analysis of the interlamination short-circuit. For a correct analysis we introduce a calibration procedure and data processing algorithm. The method with introducing a calibration procedure permits a complete analysis of the lamination insulation, both quantitatively and qualitatively. The analysis of the measuring signal, the mechanism of "core melting" and the comparison of the measuring methods are treated in detail in this article.

Analysis of magnetic characteristics of three-phase reactor made of grain-oriented silicon steel

Flux and iron loss distributions of three-phase reactor are analyzed using the finite element method considering 2-D B-H curves and iron losses in arbitrary directions which are measured up to high flux density. It is shown that the total iron loss of reactor yoke does not change so much by the yoke dimension, although the local iron loss is increased when the width of yoke is decreased. The experimental verification of flux and iron loss distributions are also carried out.

123 カード端末用直線駆動薄型発電機の発電特性

We measured the average power of thin linear-driven generators for use in card-type mobile communication terminals, which produce electricity from mechanical movement. A Long Voice Coil Generator driven by free fall energy, stroke length : 30 mm , yoke width : 120 mm, and thickness : 12 mm generates 6.7 mW with efficiency of 51%. A cellular phone sized-Voice Coil Generator driven by free fall energy and a spring, stroke length : 50 mm , yoke width : 20 mm, thickness : 12 mm generates 9.6 mW with efficiency of 32%.

1102 力学的エネルギーによって駆動するカード端末用薄型発電機の発電特性

We measured the average power of thin linear-driven generators for use in card-type mobile communication terminals, which produce electricity from mechanical movement. A cellular phone sized-Voice Coil Generatorl driven by energy and a spring, stroke length : 50mm, yoke width : 20mm, thickness : 12mm generates 9.6mW with efficiency of 32%. When the VCG1 is oscillated at about 5.8Hz with amplitude of 5mm, the generated electric power is 38mW and by shaking the generator for about 6 hours, a 20-farad super capacitor was charged to 2V. The FM transmitter, whose power consumption is 9.6mW, operated for 37 minutes by the stored power.

Iron loss measurement device under rotating magnetic field

The authors deal with measurement of iron losses under a rotating magnetic field for electrical steel alloys used in the building of rotating electrical machines. The authors note the main characteristics needed by such devices. They then describe the realisation and the use of a machine built in the laboratory. Test results obtained for two kinds of magnetic sheet show the conjunct influences of the classical electromagnetic parameters (fundamental frequency, average flux density) and the machine design parameters closely linked to the sheet anisotropy (wavelength, radial width of the yoke). Finally, the consequences for machine design are highlighted.

High frequency head and playback model for thin-film recording heads

A thin-film head field and readback model that allows for eddy currents has been proposed and used to compute complex head efficiency, inductance, anomalous (ac) resistance, head saturation fields and locations, as well as the digital playback parametrics high and low frequency amplitude, resolution, PW-50, and maximum overwrite fields with a fair amount of accuracy. The head model solves for the time-dependent vector potential in a geometry that closely resembles a modern three dimensional thin-film recording head, including variable pole and yoke width, thickness, permeability, resistivity, neck angle and other geometrical parameters. Readback emulation is done with a discrete Fourier version of the reciprocity integral using Szczech fields and arctan transitions, along with complex efficiencies from the head model. Detailed comparisons with experimental observations are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An Fast Extraction Instrument of Low Charging Voltage with Small Residual Field using Series Blumlein Line Modulators.

A kicker magnet and a pulse modulator with a low charging voltage and a short rise time are designed and fabricated for an extraction instrument of an 1GeV electron synchrotron of Mitsubishi Electric Corp. The kicker magnet is a lumped type one with a C type ferrite yoke. The gap height of the magnet is 15mm and the yoke width is 30mm. Total length of the magnet is 0.6m and the inductance is about 1.5μH.The effect of the residual magnetic field of the magnet on the low energy electron beam is studied by a beam tracking method. The results show the residual field must be lower than 1 G to obtain enough dynamic aperture of the low energy beam.The modulator consists of two Blumlein line modulators, whose inpedance are 75Ω, and is switched by a single thyratron. At the magnet, the lines are connected in series such that the inner conductor of one line is connected to the outer conductor of the other line. Then, the current in each line are added at the kicker magnet. In our system, the magnet is connected to the modulators with a mismatched resistor. Therefore the current has a damping oscillation waveform.The rise time of the current is about 40ns and the charging voltage of the modulator at the extraction from the synchrotron is no more than 40kV and which is a quarter of the voltage when a conventional P. F. N type modulator is used. The flatness of the waveform is less than ±1% and the stability is no more than 0.1%. The restriction of the residual field is satisfied by using the damping oscillation waveform of the current. The measured value of the residual field is reduced by factor 4 (0.5G) compared with the one by a rectangular waveform.At the extraction operation, successful extraction of eight bunches from fifteen bunches in the synchrotron are measured by a wall current monitor at the extraction transport line.

A study of popcorn noise for thin film heads

The magnetic domains of the yoke and heat generated in coils were investigated as possible sources of popcorn noise. It was found that the movement of the magnetic walls was the primary factor affecting the noise. When the magnetic walls were hard to move as the number of the magnetic domains increased the popcorn noise was difficult to observe. The magnetic domain configuration of the yoke was optimized by changing the shape and Fe-Ni composition of the yoke. The appearance probability of popcorn noise decreased by 60% as the Fe component was changed from 18.6 wt.% to 17.6 wt.%. The appearance probability of popcorn noise decreased by 70% as the yoke width was changed from 170 mu m to 80 mu m. >