Effects of armature reaction on the performance of a claw pole motor with soft magnetic composite stator by finite-element analysis

We investigated the effects of armature reaction on the performance of a three-phase three-stack claw pole motor with soft magnetic composite stator core by using three-dimensional finite-element analysis (FEA), which is an effective approach to accurately compute the parameters and performance such as the back electromotive force (EMF), core losses, and winding inductance at various saturation levels. The motor is rated as 500 W at 1800 rpm when the stator current is 4.1 A, driven by a sensorless brushless DC scheme. Because of the armature reaction, the back EMF produced by the rotor permanent magnets and the developed torque is reduced by about 3.3% at the rated load, and the core losses increase drastically by 41% from no-load to full-load. The winding inductance is computed with different loads at different rotor angles. © 2007 IEEE

Accurate determination of parameters of a claw-pole motor with SMC stator core by finite-element magnetic-field analysis

Effective and accurate prediction of key motor parameters, such as winding flux, back electromotive force, inductance and core losses, is crucial for design of high-performance motors. Particularly, for electrical machines with new materials and nonconventional topology, traditional design approaches based on the equivalent magnetic circuit, empirical formulas and previous experiences cannot provide correct computation. The paper presents accurate determination of major parameters of a three-phase three-stack claw-pole permanent-magnet motor with a soft magnetic composite (SMC) stator core by finite-element analysis of the magnetic field. The effects of magnetic saturation and armature reaction are considered. The theoretical results by numerical analysis are validated by the experiments on the claw-pole SMC-motor prototype

A practical circuit model of high frequency transformers in power electronic systems

This paper presents a practical circuit model of high frequency transformers in power electronic systems. All types of core losses (ie. the hysteresis, classical eddy current and anomalous losses) are included in the model. the thermal effect on magnetic hysteresis, the skin effect of eddy currents in magnetic cores and the effect of stray capacitances are also considered. This model can therefore accurately predict the performance and core losses of transformers used in high frequency switching circuits. The practical methods for determining the circuit parameters are developed and presented in the paper, providing crucial benefit for practical applications. The developed model has been applied to simulate the performance of a 500 W transformer in a full bridge inverter operated with square waveform voltage excitation of 25 kHz. The simulations are validated by the experimental results. © Institution of Engineers, Australia 2007

Effect of armature reaction of a permanent-magnet claw pole SMC motor

The finite-element method enables an accurate analysis for the study on effects of armature reaction in electromagnetic devices, particularly those with complex structures and three-dimensional (3-D) magnetic flux paths. This paper investigates the effects of armature reaction on the parameters and performance of a permanent-magnet (PM) claw pole motor with soft magnetic composite (SMC) core, based on the magnetic field analysis using the 3-D nonlinear time-stepping finite-element method. The current in the stator winding produces a magnetic field, which interacts with the air gap field generated by the rotor magnets. Consequently, the air gap flux density profile against the rotor position produced by the rotor magnets deviates, and so does the back electromotive force. Since the stator field also changes the local saturation level of the magnetic core, the winding inductance varies with both the rotor position and stator currents. The inclusion of these effects in terms of parameter variations in the motor model is important for accurate performance analysis. On the other hand, the pattern of inductance against the rotor position and stator currents can be employed to effectively predict the rotor position at standstill and low speeds for robust sensorless control. The parameter computations are verified by experimental results on the PM claw pole SMC motor prototype. © 2007 IEEE

Performance analysis of a linear motor with HTS bulk magnets for driving a prototype HTS maglev vehicle

This paper presents the performance analysis of a linear synchronous motor which employs high-temperature superconducting (HTS) bulk magnets on the mover and normal copper windings on the stator. The linear motor is designed to drive a prototype HTS maglev vehicle in which the mover is suspended by the levitation force between HTS bulks on the mover and permanent magnets on the ground. Finite element magnetic field analysis is conducted to calculate the major parameters of the linear motor and an equation is derived to calculate the electromagnetic thrust force. Theoretical calculations are verified by the measured results on the prototype. © (2013) Trans Tech Publications, Switzerland

Medium-frequency-link power conversion for high power density renewable energy systems

Recent advances in solid-state semiconductors and magnetic materials have provided the impetus for medium frequency-link based medium voltage power conversion systems, which would be a possible solution to reducing the weight and volume of renewable power generation systems. To verify this new concept, in this paper, a laboratory prototype of 1.73 kVA medium-frequency-link power conversion system is developed for a scaled down 1 kV grid applications. The design and implementation of the prototyping, test platform, and the experimental results are analyzed and discussed. It is expected that the proposed new technology would have great potential for future renewable and smart grid applications. © 2013 IEEE

A new multiple regression approach for the construction of genetic regulatory networks

Objective: Re-construction of a genetic regulatory network from a given time-series gene expression data is an important research topic in systems biology. One of the main difficulties in building a genetic regulatory network lies in the fact that practical data set has a huge number of genes vs. a small number of sampling time points. In this paper, we propose a new linear regression model that may overcome this difficulty for uncovering the regulatory relationship in a genetic network. Methods: The proposed multiple regression model makes use of the scale-free property of a real biological network. In particular, a filter is constructed by using this scale-free property and some appropriate statistical tests to remove redundant interactions among the genes. A model is then constructed by minimizing the gap between the observed and the predicted data. Results: Numerical examples based on yeast gene expression data are given to demonstrate that the proposed model fits the practical data very well. Some interesting properties of the genes and the underlying network are also observed. Conclusions: In conclusion, we propose a new multiple regression model based on the scale-free property of real biological network for genetic regulatory network inference. Numerical results using yeast cell cycle gene expression dataset show the effectiveness of our method. We expect that the proposed method can be widely used for genetic network inference using high-throughput gene expression data from various species for systems biology discovery. © 2009 Elsevier B.V.postprin

B-H relations of magnetorheological fluid under 2-D rotating magnetic field excitation

This paper presents the investigation of the B-H relations of a magnetorheological (MR) fluid under one-dimensional (1-D) alternating and two-dimensional (2-D) rotating magnetic field excitations where B is magnetic flux density and H is magnetic field strength. The measurement is carried out by using a single sheet tester with an MR fluid sample. The measurement principle and structure of the testing system are described. The calibration of the B and H sensing coils are also reported. The relations between B and H on the MR fluid sample under 2-D rotating magnetic field excitations have been measured and compared with the results under 1-D excitations showing that the B-H relations under 2-D excitations are significantly different from the 1-D case. These data would be useful for design and analysis of MR smart structures like MR dampers. © 2013 IEEE

Design and Electromagnetic Analysis of a HTS Linear Synchronous Motor

High temperature superconducting (HTS) linear synchronous motor (LSM) integrated with HTS magnetic levitation system, can realize self-levitation and self-guidance without any sliding friction, which will have important applications in many fields such as electromagnetic aircraft launch system, maglev transportation. This paper presents the design and electromagnetic analysis of a HTS LSM, which is levitated by a magnetic levitation system consisting of HTS bulkspermanent magnet (PM) guideways. Numerical analysis and magnetic field finite element analysis (FEA) methods are applied to analyze the thrust, levitation and guidance force characteristics, and the electromagnetic performance of HTS LSM under no-load and load situations are studied with the analysis results are given. Finally, the primary motor running testing results are provided

Development and application of a loop-mediated isothermal amplification method for rapid detection of Haemophilus parasuis

Haemophilus parasuis is the causative agent of Glässer’s disease that has received much attention recently, due to the increasing economic losses this disease inflicts upon the pig industry worldwide. In this study, loop-mediated isothermal amplification method (LAMP) methodology was designed for diagnosing H. parasuis infections and tested against 56 clinical samples. Two sets of primers for LAMP were designed based on the H. parasuis inf B gene sequence. Target DNA was amplified and visualized on agarose gels after 50 min incubation at 63°C. The LAMP amplicon was also directly visualized in the reaction tubes by the naked eye following the addition of SYBR green I. The detection limit of the inf BLAMP method was 10 cfu mL-1, that was 10 times more sensitive than conventional PCR. Furthermore, positive rates of H. parasuis detection using inf B-LAMP were higher (46.4%, 26/56) than the rates obtained with conventional PCR (33.9%, 19/56). inf B-LAMP specificity analysis demonstrated no crossreactivity with any other swine pathogens. In conclusion, inf B-LAMP was more sensitive and faster and could be carried out in the absence of expensive equipment. Furthermore, the visual readout demonstrated great potential for the use of inf B-LAMP in the clinical detection of H. parasuis.Key words: Glässer’s disease, Haemophilus parasuis, inf B, PCR, LAM