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The conventional linear flux-switching permanent-magnet (FSPM) motors directly split from a rotary FSPM motor suffer from drawbacks such as unbalanced magnetic circuit of end coil, bigger cogging force, and force ripple. In this paper, to reduce cogging force and thrust force ripple, some complementary and modular linear FSPM (LFSPM) (MLFSPM) motors with mover/stator pole pitch ratio \taum/\taus of about one, namely, \taum/\taus = 10/12, 11/12, 12/12, 13/12, 14/12, 15/12, will be investigated using finite-element method (FEM) and experimental method at first. Then, another new LFSPM motor with \taum/\taus =\break 3 is analyzed. Based on \taum/\taus = 3, some new MLFSPM motors are designed, investigated, and compared using FEM. To fully investigate these motors, the optimal MLFSPM motor with \taum/\taus = 3 is quantitatively compared with the two optimal motors with \taum/\taus \approx 1. Finally, the general design principle for this series of MLFSPM motors with different \taum/\taus values is concluded. [ABSTRACT FROM PUBLISHER]

Fault current limiters are devices that limit currents in electrical networks during a fault event, such as power lines touching or arcing due to tree branches. In this paper, two designs for small-scale saturated-core fault current limiters are discussed: one that uses DC coils to saturate the cores, and one that uses a hybrid design with DC coils and permanent magnet blocks. The hybrid design is found to meet the same performance criteria with a 50% reduction in energy consumption when compared to the DC coil only design. [ABSTRACT FROM AUTHOR]

Linear flux-switching permanent magnet (LFSPM) motors with both permanent magnets and armature windings on the short primary mover have attracted considerable attention due to their simple and cheap stator which only consists of iron. Hence, this kind of liner motor is very suitable for long stator applications such as in urban rail transportations. However, the conventional LFSPM motors directly split from rotary FSPM motor suffer from drawbacks such as unbalanced magnetic circuit of end coil, heavy mover, and bigger cogging force and force ripple. Modular LFSPM (MLFSPM) motors can mitigate the problem of unbalanced magnetic circuit of end coil. But some MLFSPM motors with different stator/mover pole pitch \taus/\taum=12/14, 12/10 don't have complementary phase armature windings, which will lead to asymmetrical and non-sinusoidal back-electromotive force, bigger cogging force and thrust force ripple. The key of this paper is to propose, investigate, and compare four complementary and modular structures for the LFSPM motors with different \taus/\taum. The electromagnetic performance and dimensions of the proposed complementary MLFSPM motors with different \taus/\taum are investigated, compared and confirmed by the means of finite element analysis and experimental results. Based on the analysis results, two complementary MLFSPM motors with \taus/\taum=12/13 are chosen to be the two best motors, which can offer the biggest thrust force, relatively smaller cogging force and thrust force ripple, and shorter mover length. [ABSTRACT FROM AUTHOR]

A saturated core fault current limiter (FCL) is a device that is designed to limit the fault currents in electrical energy networks and consequently, protect existing network equipment from damage. Due to complex nonlinear magnetic properties, the performance of saturated core FCLs has largely been characterized through experimentation and finite-element analysis simulations. Although both of these techniques are quite accurate, they are time consuming and do not describe the behavior of FCLs in actual electrical networks. This has led to an increasing demand for an accurate analytical model that is suitable for transient network analyses. This paper presents the development of an analytical model of a single-phase open-core FCL, which accurately describes the nonlinear magnetic properties of the FCL through a reduced reluctance approach. The extension of this model to other saturated core FCL arrangements (such as closed core) is also discussed. [ABSTRACT FROM AUTHOR]

In this paper, a new technique for estimation of airgap length in magnetically levitated systems (MagLev) is introduced. The proposed method makes use of the embedded airgap information in the inductance of an active phase in a hybrid MagLev system. Terminal measurements are used along with the phase voltage equation to estimate airgap length by the virtue of an existing one-to-one correspondence between inductance and airgap length. Sensitivity analysis will be carried out to illustrate the impact of changes in MagLev's geometry and current sensor resolution on the accuracy of the proposed method. Based on experimental results, it will be shown that the proposed sensorless method performs well both at standstill and moving conditions. [ABSTRACT FROM AUTHOR]

The need for testing magnetic materials used in electric machine laminations and measurements under a rotating field is of importance in machine design. In order to obtain satisfactory experimental data, the design of the measurement apparatus deserves particular attention. The purpose of this paper is to propose a novel design of a magnetic circuit based on the Halbach array, which generates a uniform flux density inside the test specimen for the measurement of rotational core loss. The proposed design is simulated and prototyped, and experimental tests are performed on two different samples of M19 gauge-24 and M36 gauge-29 silicon steel at three different frequencies (60 Hz, 400 Hz, and 1 kHz). The field-metric method is used in this work to evaluate the rotational core losses. [ABSTRACT FROM PUBLISHER]

International standards for testing soft magnetic materials require that the magnetic flux density remain sinusoidal with respect to time. Traditionally, this has been achieved via control of the magnetic flux using either analog feedback, which provides real-time control, or iterative digital feedback, which yields more accurate solutions with the cost of increased convergence time. In certain applications, such as magnetic nondestructive testing, rapid convergence of multiple interacting flux controlled channels is required. In this paper, a multichannel flux controller design is presented that combines the real-time performance of analog feedback with an iterative digital feedback algorithm to reduce error. The system demonstrates a 95% reduction in convergence time at power line frequencies over a comparable system using only digital feedback. Several examples of the system's ability to control arbitrary periodic waveforms are presented over the frequency range from 0.735 Hz to 100 Hz. Sinusoidal form factor errors are shown to be 0.1% from 2 Hz to 100 Hz across four strongly coupled channels with highly nonlinear magnetizing conditions. A detailed description of both analog circuit and digital algorithms is provided. [ABSTRACT FROM PUBLISHER]

The paper describes the dipole electromagnet XBB to be used in the XFEL systems for longitudinal compression of beam bunches. [ABSTRACT FROM PUBLISHER]

This paper summarizes the results of the static structural analyses, which were conducted in support of the ITER magnet feeder design with the aim of validating certain components against the structural design criteria. While almost every feeder has unique features, they all share many common constructional elements and the same functional specifications. The analysis approach to assess the load conditions and stresses that have driven the design is equivalent for all feeders, except for particularities that needed to be modeled in each case. The mechanical analysis of the feeders follows the sub-modeling approach: the results of the global mechanical model of a feeder assembly are used as input for the detailed models of the feeder' sub-assemblies or single components. Examples of such approach, including the load conditions, stress assessment criteria and solutions for the most critical components, are discussed. It has been concluded that the feeder system is safe in the referential operation scenarios. [ABSTRACT FROM PUBLISHER]

CERN is pursuing a small scale R&D on a fast cycled superconducting dipole magnet (FCM) of interest for the upgrade plan of the LHC accelerator complex. The FCM dipole prototype being built has a number of novel features if compared to other magnets for similar applications. In this paper we describe the magnet design, and its expected performance, focusing especially on the novel features (magnetic circuit, mechanical supports, cooling) and on the details of the manufacturing procedure (coil winding and impregnation, joints, instrumentation and quench protection). [ABSTRACT FROM PUBLISHER]

MRI magnets and other magnets that have a low current and high self-inductance are passively quench-protected with a system that includes sub-divided coils with resistors and diodes that are in parallel with sections of the coils. The primary purpose of coil sub-division is to protect the coil from the high voltages that can occur during a quench. In the event of a lead failure (conventional or superconducting) between the coil and its power supply or its persistent switch, the total current in the coil flows through the diodes and resistors in parallel with the coil. When a lead fails, the current decay time constant for the coil current can be quite long. It is desirable that the coil quench in a time that is short compared to the coil current decay time constant. Experience shows that the heating from the resistors and diodes will eventually quench the magnet. This paper presents methods for shortening the time between a lead failure or a persistent switch failure and the eventual magnet quench. [ABSTRACT FROM PUBLISHER]

During the last decade orthogonal fluxgates have been mainly manufactured using magnetic microwire surrounded by a pick-up coil. This structure has several advantages, however it employs a finite length core as well as traditional orthogonal fluxgates based on cylindrical bulk core do. The measured field on axial direction is applied on a magnetic core with open magnetic circuit, which is therefore affected by the length of the wire. In this paper we compare sensor heads with wire-core having different length: the resulting noise is significantly lower for longer core (about 4 pT/\surdHz at 1 Hz vs. 7 \div 8 for short wire). In fact, the terminations appear less saturable than the central part of the wire. Moreover, we show how the ends contribute less to the total sensitivity. Finally we model by FEM simulation the structure of the wire and we show that the different response of the wire to the axial field is fully described by demagnetizing effect. Therefore, we suggest to use a long wire keeping the termination if possible out of the pick-up coil in order to obtain the output signal from the more uniform part of the wire. [ABSTRACT FROM PUBLISHER]

This paper describes the detailed design of the quench protection circuits (QPCs) for the superconducting toroidal field (TF) and poloidal field (PF) magnets of the satellite tokamak JT-60SA, which will be installed in Naka, Japan. The nominal currents to be interrupted and the maximum reapplied voltages are 25.7 kA and 2.8 kV for the TF QPCs and 20 kA and 5 kV for the PF QPCs. The innovative solution proposed in the QPC design is based on a hybrid circuit breaker (CB) composed of a mechanical bypass switch for conducting the continuous current, in parallel to a static CB for current interruption. The main choices of the final design are presented and discussed, either to confirm or to update and complete the study performed at the conceptual design level. [ABSTRACT FROM PUBLISHER]

This paper presents a new signature for detection of rotor faults in induction motors, such as eccentricity and broken rotor bars, that uses the external magnetic field analysis. The proposed method is based on the variations of axial flux density in the presence of these faults. The low frequency part of the magnetic field spectrum is particularly analyzed. The analysis is realized through a machine modeling based on permeance circuit under eccentricity fault and also by machine modeling based on coupled magnetic circuit theory under broken rotor bars fault. Analytical relations which describe the machine operation under broken bars fault highlight the influence of speed variation to modify the low frequency components of the external magnetic field. The theoretical results have been validated by experimental measurements. In particular, an inverse stator cage induction machine have been used to measure the bar currents under healthy and faulty cases. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel linear electromagnetic actuator (LEA) for auto-focusing of compact phone cameras. An LEA consists of permanent magnets, iron cores, and coils, which are all magnetic circuit components. When coils are powered, induced magnetic field generates N and S poles around iron cores. Thus, unlike voice coil motors (VCMs) that employ the Lorentz force, the motion of the moving part in this study is arisen from a property-same poles repel each other while opposite poles attract each other. When compared to conventional VCM actuators in simulation results, the proposed LEA generates larger force, whereas using smaller current. [ABSTRACT FROM AUTHOR]

This paper proposes a novel radial hybrid magnetic bearing (RHMB), which has integrative magnetic pole boards and continuous working air gaps that reduce the hysteresis and eddy-current losses of the traditional homopolar structure. Its configuration and working principle are introduced. The bias and control magnetic circuits of the RHMB are analyzed with the equivalent magnetic circuit method. Mathematical models, from which the force-displacement and force-current relationships are derived, are built. The method for the rudimentary design of RHMB parameters is illustrated, through which a prototype RHMB for a reaction flywheel system is designed and assembled. Its performance and characteristics are calculated and analyzed with the obtained models and relationships. The results show that in its air gaps, the novel RHMB can generate a continuous and uniform bias magnetic field, which reduces the hysteresis and eddy-current losses and enhances the radial load capacity and axial passive resilience. The bias fluxes of all poles are decoupled from each other at all times. Although the control fluxes of the two channels are slightly coupled when the rotor is not in the central position, the coupling force-current stiffness is very low and can be ignored. These attributes simplify the design of the control system. The novel RHMB is especially suitable for high-speed and low-loss circumstances. A pair of RHMBs are used for the reaction flywheel, and for maintaining suspension of the rotor at the spin speed of 0–6000 rpm. [ABSTRACT FROM AUTHOR]

This paper presents novel overlapping ironless windings for permanent magnet planar motors, which have high winding factors and make full use of the magnetic field of the magnet array in the planar motor. A simple analytical model of the planar motors is developed and validated by finite-element method first. Then the winding factors of the ironless windings are derived and used to simplify the analytical model. Furthermore, the design rules of the ironless windings for the planar motor are obtained from the analytical model with winding factors and the ironless windings are optimized for maximum steepness of the planar motor. Compared with the nonoverlapping ironless windings, the novel overlapping ironless windings have a much (up to 25%) larger force with the same copper loss and nearly the same size when the coils of the windings have a large length/width ratio. [ABSTRACT FROM PUBLISHER]

This paper proposes a mixed experimental/numerical technique to characterize magnetic laminations in the direction normal to their surface. The principle, which uses static excitation to avoid errors caused by eddy currents, is explained and a specific test bench is proposed. Measurements of the magnetic flux density are made using a sensor being moved in and out of the air gap and are supplemented by 3-D numerical modeling where the final characteristic is obtained through iterations until the computed and measured values agree within assumed tolerance. Comparisons with previously published approach based on an analytical model are made and specific properties of the characteristic of anisotropic laminations are discussed. [ABSTRACT FROM PUBLISHER]

Functional electrical stimulation (FES) is a type of therapy used for paralyzed patients. In FES, the implant direct feeding method is an ideal stimulus method. In this method, small stimulators are implanted in the paralyzed limbs, and magnetic coupling is used to simultaneously power the implants and enable digital communication with the mounted system. To realize this method, we have developed an implant antenna (magnetic connective dual-resonance antenna) that can transmit as well as receive signals and a mounted communication system that is responsible for supplying power and communication from outside the body to the implanted antenna inside of the body. However, to guarantee safe stimulation, this system requires the closed-loop control function. For this purpose, we have proposed a communication protocol that is inexpensive, and a new communication system that supports bidirectional communication. In this paper, we present the new protocol, the composition and mechanisms of the proposed system, and the experimental results that verify the efficiency of this system. [ABSTRACT FROM AUTHOR]

This paper presents an optimization of voice coil motor (VCM) used in ultra-precision motion stages based on an improved magnetic equivalent circuit (MEC) model. The modified MEC model takes into consideration the nonlinear saturation effect of ferromagnetic material by segmentation, and estimates the magnetic flux density in air gap of VCM in a more precise way. The results of experiment, finite-element analysis, and MEC model are compared to validate the correctness of the improved MEC method. A new optimization criterion is used to measure dynamic response and heat dissipation of VCM simultaneously. The geometric parameters of VCM are optimized, and the resulting VCM is proved to have a better dynamic response and lower heat dissipation. [ABSTRACT FROM PUBLISHER]

This paper proposes a ferro–nickel (Fe–Ni)/PZT H-type fork magnetoelectric (ME) composite structure and an energy management circuit for ME energy harvesting. The resonant fork composite structure with a high Q value shows a higher ME voltage coefficient and a stronger power coefficient compared with the conventional rectangular composite structure. The resonant fork composite structure can obtain an output power of 61.64 \mu\W at an ac magnetic field of 0.2 Oe. The ME sensitivity of the fork structure reaches 11 V/Oe. For weak magnetic-field environment, an active magnetic generator and a magnetic coil antenna underground are used for producing an ac magnetic field of 0.2–1 Oe at a distance of 25–50 m. A management circuit of the power supply with matching circuit, energy-storage circuit, and instantaneous-discharge circuit is developed suitable for weak electromagnetic energy harvesting. The management circuit can continuously accumulate weak energy from the fork composite structure for a long period and provide a high-power output in a very short cycle. While the voltage across the storage supercapacitor is over 0.36 V, the instantaneous-discharge circuit can drive a wireless sensor network node with an output power of 75 mW at a distance of over 60 m. [ABSTRACT FROM AUTHOR]

Discontinuity of magnetic circuit according to the end effect is generated in the PMLSM. Due to the unbalanced magnetic state, the unbalanced inductance and unbalanced back-EMF is produced. In this paper, the effects of circulating current due to the end effect are analyzed by FEA (Finite Element Analysis). By using FEA and DOE (Design of Experiment), an optimal design of the auxiliary-teeth model is carried out to decrease circulating current. And the effect of the unbalanced phase based on the auxiliary-teeth installation is considered. [ABSTRACT FROM PUBLISHER]

This paper describes a device capable of throwing aluminum rings in a range of a few meters. The device is a modification of the jumping-ring design invented by the American engineer and inventor E. Thomson to demonstrate his pioneering research in alternating current. We improved the magnetic circuit of this device and created a new induction coilgun based on “E-shaped” design. We experimented with this new design under laboratory conditions and simulated its behavior using an interactive software package. Finally, we concluded that this device is able to achieve a higher speed than the Thomson design with lesser power consumption. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel structure of permanent-magnet-biased axial hybrid magnetic bearing. It has four segments of poles to control three degrees of freedom (3-DOF). Based on the inner and outer air gaps in conventional axial magnetic bearings, a novel air gap, called the subsidiary air gap, is constructed between the permanent magnet and the stator poles. This air gap separates the bias flux paths from the control flux paths. As a result, lower power loss of the axial magnetic bearing can be achieved due to lower magnetic reluctance of the control flux paths. Furthermore, by means of the equivalent magnetic circuit method and the 3-D finite-element method (FEM), we analyze and model the 3-DOF axial hybrid magnetic bearing. Experimental results show that the presented axial magnetic bearing has good control performance and little coupling among X, Y, and Z directions. However, the rotational power loss will be large at high speed because of the alternating flux density in the thrust plate produced by four segments of stator poles. Therefore, we propose a novel stator, named the parallel-slot stator, and novel thrust plate to reduce the rotational power loss effectively, which is assembled by DT4 and nanocrystalline materials. Meanwhile, we have designed and assembled an axial hybrid magnetic bearing prototype with the novel stator and thrust plate, which is applied in the five-degrees-of-freedom reaction flywheel system with angular momentum of 15 Nms at 5000 r/min. It is validated by the experimental results. [ABSTRACT FROM AUTHOR]

Wendelstein 7-X (W7-X) is a superconducting stellarator under construction at the Max-Planck-Institute for Plasma Physics in Greifswald, Germany. The magnet system consists of 70 superconducting coils providing magnetic confinement-fields. Before assembly every coil had to pass an acceptance test at the French partner-institute CEA, Saclay, to examine its performance on leak tightness, high voltage strength, ampacity, and hydraulic flow at cryogenic conditions. The testing procedure was mandatory, as access for maintenance or repair after installation will not be viable. Testing followed a well specified routine including tests in warm conditions, during cool down, in cold conditions, during warm up and at last in warm conditions. Measurement was obtained firstly by the facility's instrumentation and secondly by the coil-casing's instrumentation. The received data was transmitted to different ASCII-files for each gauge. To record testing in detail, a meta-document was edited, which follows in its structure the routine mentioned above. Accordingly, the main distinctive functions of the coil during testing are recorded in so called test reports, while deviations from given thresholds and parameters are described in non conformity reports. During testing, organizational and technical challenges had to be mastered and the test program was regularly updated to meet technical improvements, manufacturing requirements and revised assembly schedules. This paper will present the acceptance test program, its development and the gained experiences. [ABSTRACT FROM AUTHOR]

A single-chip digital SQUID magnetometer integrates a sensitive analog SQUID sensor with a comparator gate and feedback circuitry on the same chip. The comparator gate is an asymmetric SQUID gate driving two DC-to-SFQ converters in series with the feedback coil. In an optimized digital magnetometer chip, sensitivity and noise level are determined by the input analog SQUID. The dynamic range of such digital chips is extremely wide enabling them to be operated in a relatively high magnetic field environment without extensive magnetic shielding. Their slew rate is determined by the frequency of an external two-phase clock. This chip simplifies room temperature electronics and, due to its digital output, can be easily multiplexed on-chip. In this paper, we describe this digital SQUID magnetometer chip and summarize our experimental results demonstrating a digital SQUID chip with sensitivity of 20 /spl mu//spl Phi//sub 0///spl radic/(Hz) and a system slew rate of 5/spl times/10/sup 6/ /spl Phi//sub 0//s at the pick up coil. [ABSTRACT FROM PUBLISHER]

In this paper, examination of the limiting value of the thrust constant of a linear DC motor (LDM) is described. The LDM under consideration is a moving coil unipolar type. We deduce a relation between the limiting value of the thrust constant LDM and the dimensions of the yokes. By comparison of the measured thrust and the magnetic field analysis (finite element method), the validity of the thrust constant limit equation is confirmed. The thrust constant limit equation qualitatively agrees with the observed result, and its maximum error is 26.0 percent. It also agrees well with the result of the magnetic field analysis. [ABSTRACT FROM PUBLISHER]