Synchronous Induction Research Articles

Natural and controlled ovulation in South American camelids.

The four species of New World camelids and 2 species of Old World camelids derived from a common ancestor in North America. The reproductive characteristics, particularly those involving ovarian function and ovulation, are remarkably similar among the 6 living species of camelids, so much so that interspecies hybrids of nearly all possible combinations have been documented. Camelids are induced-ovulators, triggered by an ovulation-inducing factor in seminal plasma. The timing and mechanism of endocrine events leading to ovulation are discussed, as well as the discovery, identification and mode of action of the seminal factor responsible. The applied aspects of our present understanding are discussed with specific reference to controlled induction of ovulation, ovarian synchronization, and superovulation. Emphasis has been given to the literature on llamas and alpacas, with some reference to studies done in wild species of South American camelids and Old World camels.

Design of Linear Absorbing Feedback

This paper considers dynamic vibration absorbers using the theory of linear control. We introduce an axiomatic definition of absorbing feedback. Next, we establish frequency domain stability criteria for the control systems with absorbing feedback by constructing a Lyapunov function and employing the Kalman–Yacubovich–Popov lemma. Finally, we demonstrate that linear absorbing feedback can be applied to suppress the vibrations of an ellastic plate with synchronous machines and induction motors and also to design ultranarrow bandpass filters.

Indirect boost matrix converter and low‐voltage generator for direct drive wind turbines

Here, a new topology for direct drive wind turbines (DDWTs) with a new power electronics interface and a low-voltage generator is presented. In the presented power electronics interface, the grid-side converter is replaced by a boost current source inverter (CSI) which eliminates the required dc-bus capacitors, resulting in an increase in the system lifetime. The inherently required dc-link inductor for this topology is eliminated by utilising the synchronous inductance of the permanent magnet synchronous generator. The control technique used for the developed DDWT is described here. The boost CSI enables conversion of a low dc voltage to a higher line-to-line voltage creating an indirect boost matrix converter, and thus, enabling the implementation of a low-voltage generator. This further enables a reduction in the number poles required in direct drive wind generators. The feasibility of the proposed generator-converter topology for DDWTs and its controllers are verified through simulations and experimental results on a laboratory scale 1.5 kW, 240 V set-up.

Research of Firing Control Model of Multi-stage Synchronous Induction Coil Launcher

The problem of firing control is a critical technology of multi-stage synchronous induction coil launcher (MSSICL). Operation with high launch efficiency of MSSICL mainly depends on each stage driving coil energized when the armature moves on the proper location. In order to solve the problem of firing control for MSSICL, the firing control model of MSSICL is built based on the dynamically simulative model and the firing control criterion. The dynamically simulative model includes the voltage equations of driving circuit and the kinematic equations. The solved method is provided. In addition, the factors that influence the solved precision of the firing control model of MSSICL are analyzed.

Research on self-consistent control strategy of multistage synchronous induction coil launcher

Trigger control strategy is of vital importance for the multistage synchronous induction coilgun (MSSICG). According to the operating principle of MSSICG, we can theoretically obtain a sustained and steady acceleration which is sufficient to push the projectile to high speed by means of continuously increasing the series of driving coils and matching with the appropriate trigger strategy. However, the transition time between the adjacent coils decreases with the increase of the projectile velocity, which leads to the weakness of the traditional position or time trigger control. In this paper, a self-consistent control strategy of MSSICG was proposed. Its accuracy and flexibility are verified through an illustrative example of a 25 stages synchronous coilgun. The results coincide well with that by finite-element method (FEM), and the error of muzzle velocity is only 3.4%. Based on this method, the influence of slip speed and rise length on the adaptive control effect is calculated and analyzed, and accordingly proposed to use variable slip speed. As far as the capacitive pulsed power supply (CPPS)-based MSSICG is concerned, the research methods and results in this paper have both theoretical and pragmatic value in simplifying the design process and improving energy conversion efficiency (ECE).

A Generator-Converter Topology With Zero DC-Link Impedance for Direct Drive Wind Turbines

A new topology is proposed for direct drive wind turbines that eliminates the use of the failure prone dc-bus electrolytic capacitor, avoids the need for a dc-link inductor by utilizing the synchronous inductance of the wind turbine permanent-magnet generator (PMG), and provides a low-voltage generator design, which decreases the amount of permanent-magnet material used in PMG, and reduces the volume and weight of the generator.

Effects of a single administration of different gonadotropins on day 7 post-insemination on pregnancy outcomes of rabbit does

This study aimed to investigate the effects of a single administration of one of three different gonadotropins on Day 7 post-insemination on ovarian activity, progesterone (P4) concentration and pregnancy outcomes of rabbit does. Multiparous, non-lactating, V-line does were artificially inseminated after synchronization and ovulation induction with equine chorionic gonadotropin (eCG; 25 IU im) and gonadotropin releasing hormone (GnRH; 0.8 μg buserelin im) 48 h later. On Day 7 post-inseminarion, does were randomly allocated into four groups (n = 40/group). Does of each group were intramuscularly injected with a single dose of one of physiological saline (placebo; control), GnRH (0.8 μg buserelin), human chorionic gonadotropin (hCG; 25 IU) or eCG (25 IU). Concentration of serum P4 was determined on Days 6, 9, 11 and 18 post-insemination. On Day 14 post-insemination, the ovaries and reproductive tracts of pregnant does were removed and weighed. Also, numbers of visible follicles, hemorrhagic follicles, corpora lutea of pregnancy (pCLs), new CLs (nCLs; formed after Day 7 post-insemination) and implantation sites were recorded. Conception rate, parturition rate, abortion rate, litter size/weight and litter viability were recorded. The highest (P < 0.05) reproductive tract and ovary weights were for eCG. The highest (P < 0.05) number of visible ovarian follicles was for eCG, whereas the lowest (P < 0.05) was for GnRH. Treatment with eCG increased (P < 0.05) numbers of pCLs and total implantation sites compared to the other groups. Treatment with GnRH or hCG increased (P < 0.05) number of nCLs compared to control and eCG. The highest rate of fetal loss was in does treated with GnRH. The concentration of serum P4 decreased (P < 0.05) following the treatment with GnRH and continued low until Day 18. However, it remained in line for control, hCG and eCG groups up to Day 11, then decreased (P < 0.05) for control and hCG on Day 18, being lower for hCG than control, while continued to increase for eCG up to Day 18. Compared to control, treatment with eCG improved (P < 0.05) conception and parturition rates by 24 and 22%; respectively, while GnRH and hCG treatments decreased (P < 0.05) them by 57 and 47.6%; respectively. Litter size and litter weight at birth were improved by eCG, but were adversely affectd by GnRH and hCG. In conclusion, a single administration of eCG 7 Days post-insemination could be recommended for improving pregnancy outcomes in rabbits.

Research on the Temperature Field of Multistage Synchronous Induction Coilgun

During coilgun launching, the driving coil and the armature will generate a lot of heat due to pulsed current. Especially in the local area of the armature, temperature may exceed the melting point because of the skin effect, so that the launching performance will be influenced. Therefore, it is very important to investigate the temperature distribution for optimizing the launcher design and improving the system efficiency. In this paper, taking a six-stage induction coilgun for an example, an electromagnetic-thermal coupled simulation model is built using the current filament method. The temperature distribution is calculated under the circumstance of unidirectional coupling and bidirectional coupling for the multiphysics solutions. Comparing the two simulation results, the temperatures of the driving coils are both low and have unconspicuous effect on the system performance. The area of high temperature rise on the armature is located in the outer surface and the rear part. The temperature rise from the unidirectional coupling calculation is higher than that from the bidirectional coupling calculation. The calculation result shows that the temperature rise changes the material conductivity, and the current distribution in the armature is redistributed. So that it leads to the local temperature reduction. The material of the armature may influence the system performance and temperature because the conductivity changes the distribution of the induced current. The armatures made up of copper and aluminum are simulated, respectively. Simulation result shows that the velocity profile is identical, but the temperature rise of the copper armature is lower than that of the aluminum armature for the same mass. Therefore, the material conductivity should be considered for the design of the high-speed launching. In order to validate the simulation results, a six-stage coilgun has been built. Comparing with the test results, the simulation result is validated.

Armature Structure Research of a Synchronous Induction Coil Launcher

Armature is very important for a synchronous induction coil launcher which can transform the electric energy to kinetic energy and push the load forward. The structure of the armature will influence the kinetic energy conversion efficiency directly. This paper analyzes the armature structure of a capacitor-driven synchronous induction coil launcher. Length and thickness of the armature are analyzed that how these parameters influence the maximum velocity and system efficiency of the launcher. Current filaments model is used to calculate the motion characteristics of a tubular linear induction motors, which is verified by an experiment and finite-element code. Genetic algorithm optimizer is used to calculate the best trigger times of the coils and the maximum velocity under the conditions of different length and thickness of the armature. It is shown that when the armature mass is fixed, length and thickness of the armature will greatly increase the velocity of the armature. The best length of the armature should be almost 2–2.5 times the length of the coil. The best thickness of the armature could be estimated by skin depth.

Multiobjective Optimization of Multistage Synchronous Induction Coilgun Based on NSGA-II

The structure and trigger control strategy have become the most important factors that restrict the performance of the multistage synchronous induction coilgun (MSSICG). However, it is still a difficult task to design MSSICG under overload constraint due to coupling between the multiple parameters. In this paper, the maximization of the emission efficiency and acceleration stationarity is treated as a multiobjective optimization problem. By analyzing the relationship between the number of turns and the other structural parameters of the launch, the multiobjective optimization model of MSSICG is established by the current filament method which was verified by the experimental data and finite-element method. And then the second generation nondominated sorting genetic algorithm (NSGA-II) and multiobjective particle swarm optimization (MOPSO) were employed to optimize the model in order to maximize the energy transfer efficiency while achieving the smooth acceleration of the armature. With the formulated optimization model, a five-stage synchronous induction coilgun is optimized as a special case. A decision-making procedure based on the fuzzy membership function is used for obtaining best compromise solution from the set of Pareto-solutions obtained through NSGA-II and MOPSO. In addition, the optimization performance of the proposed multiobjective optimization model and the single-objective optimization model of the MSSICG was compared. The result of optimization shows that the proposed multiobjective optimization model of MSSICG can effectively improve the performance of the coilgun compared with the single-objective optimization model which takes of the launch velocity and overload acceleration as the combination objective function or only the launch velocity.

Investigation of Magnetic Field Arrangement on Launching Performance of Multistage Synchronous Induction Coilgun

For the multistage induction coilgun, many researchers pay great attention to improving the system efficiency. The directions of magnetic field generated by the driving coils are consistent for conventional coilgun, because it is convenient to analyze acceleration characteristic and stress status for the armature in the barrel. In this paper, the launching performance of multistage induction coilgun is investigated in terms of different directions of magnetic field in order to improve the system efficiency. A field-circuit coupled model for a 6-stage coilgun is built. The simulation for the consistent direction of magnetic field is calculated. For the same parameter setup, the directions of magnetic field generated by the last three stages current are changed. The simulation results show that the armature endures a large braking force when going through the last three stages, and the velocity drop is obvious. Meanwhile, the currents in the last three stages are very large. The distribution of the current density and the magnetic field during the transition process of magnetic field are analyzed. The reason for velocity drop when changing the direction of magnetic field is discussed. A method that the trigger position is adjusted for the armature is proposed. The simulation results show that the armature can be accelerated to a higher speed on condition of inconsistent direction of magnetic field with adjusting the trigger position. It is feasible to improve the system launching performance through changing the direction of magnetic field. A 15-stage coilgun is built to validate the method. The experimental results show that the velocity and system efficiency are increased dramatically through changing the direction of magnetic field. It provides valuable reference for multistage induction design.

Dynamic Modeling and Simulation of Short-Duration Over-excitation Phenomenon in Hysteresis Motor

The hysteresis motor is a well-known synchronous motor that is used in special small power, high speed applications. Dynamic modeling and analysis of this motor is more complicated than permanent magnet synchronous motors (PMSMs) or induction motors (IMs) due to nonlinear behavior of rotor magnetic material. Short over-excitation is a unique phenomenon that only occurs in hysteresis motor in which the terminal voltage increase at synchronous speed for a short duration, and then continuously is decrease to initial value. Therefore, the input current is reduced, this leads to more power factor and efficiency enhancement. Till now, there isn’t any analytic dynamic model of this phenomenon. In this paper, based on a novel dynamic model of hysteresis motor, the over-excitation phenomenon is investigated and transient performance of the motor during over-excitation is simulated via Simulink.

Nonlinear tracking control for sensorless permanent magnet synchronous motors with uncertainties

The recent advanced solution in Marino, Tomei, and Verrelli (2013) to the tracking control problem for sensorless IMs with parameter uncertainties is translated on the basis of letter swap connections between the models of (nonsalient-pole surface) permanent magnet synchronous motors (PMSMs) and induction ones (IMs). The (stability proof-based) nonlinear adaptive position/speed tracking control for sensorless PMSMs (with simultaneous estimation of uncertain constant load torque and stator resistance), which is accordingly obtained by exploring and decoding the design paths in Marino et al. (2013) and which surprisingly represents a simple generalization of the controller in Tomei and Verrelli (2011), constitutes an innovative solution to the related open problem. Illustrative experimental results are included.

Cellulolytic RoboLector \u2013 towards an automated high-throughput screening platform for recombinant cellulase expression

BackgroundCellulases are key player in the hydrolyzation of cellulose. Unfortunately, this reaction is slow and a bottleneck in the process chain from biomass to intermediates and biofuels due to low activities of the enzymes. To overcome this draw back, a lot of effort is put into the area of protein engineering, to modify these enzymes by directed evolution or rational design. Huge clone libraries are constructed and have to be screened for improved variants. High-throughput screening is the method of choice to tackle this experimental effort, but up to now only a few process steps are adapted to automated platforms and little attention has been turned to the reproducibility of clone rankings.ResultsIn this study, an extended robotic platform is presented to conduct automated high-throughput screenings of clone libraries including preculture synchronization and biomass specific induction. Automated upstream, downstream and analytical process steps are described and evaluated using E. coli and K. lactis as model organisms. Conventional protocols for media preparation, cell lysis, Azo-CMC assay and PAHBAH assay are successfully adapted to automatable high-throughput protocols. Finally, a recombinant E. coli celA2 clone library was screened and a reliable clone ranking could be realized.ConclusionThe RoboLector device is a suitable platform to perform all process steps of an automated high-throughput clone library screening for improved cellulases. On-line biomass growth measurement controlling liquid handling actions enables fair comparison of clone variants.

Characteristics Analysis of PM Type Offshore Wind Power Generator with Dual Inverters according to Number of Per Pole Per Phase

This paper presents several characteristics of performance in dual 3-phase machine for offshore wind power generator according to number of per pole per phase, ‘q’. With the same rotor structure, the number of turn per coil is adjusted to the aim of same electrical loading. By using FEA, self-, mutual- and synchronous inductance are calculated. In addition, magnetic flux density, flux linkage, torque ripple, cogging torque, and demagnetization withstand are investigated. In case of q=1, the model can have large inductance, low mutual coupling between two phase coils, and good demagnetization withstand but it has large torque ripple and cogging. On the contrary, the generator with q=2 can have low torque ripple, cogging and relatively high average torque because of low MMF harmonics but it has high mutual coupling due to low inductance and bad demagnetization withstand.

Variable-speed PM synchronous motors with ferrite excitation

The standard motor for variable-speed main drives is the induction motor (IM). In comparison to synchronous machines (SYM), induction motors show the disadvantage of additional ohmic losses in the rotor. Therefore, especially low-power induction motors are not able to reach energy efficiency levels as high as IE4. The transition of motor technology from induction motors to synchronous motors with ferrite excitation provides the opportunity to increase motor efficiency without using expensive rare-earth magnets. Therefore, this paper deals with the steady-state modeling, simulation and design of PM synchronous motors with ferrite excitation in respect of reaching the highest possible motor efficiency. Due to the comparatively poor magnetic parameters of the ferrite magnet, a motor design using the flux concentration effect has to be used. An analytical approach based on a magnetic network is developed to describe the steady-state operating behavior of the ferrite excited PM synchronous motor. The non-linear network equations are solved by applying the Newton-Raphson Method. Due to short calculation times and a high flexibility in respect of the design of a whole product series, the analytical approach is preferred to a numerical approach. To validate the simulation results, a prototype is designed based on a fundamental induction motor. Finally, the test of the prototype in laboratory allows a comparison between simulation and measurement as well as between ferrite excited PM synchronous motor and induction motor.

Improved hybrid method to calculate inductances of permanent magnet synchronous machines with skewed stators based on winding function theory

An improved hybrid method combining two dimensional (2D) finite element analysis (FEA) and the analytical method is put forward to calculate the stator winding inductance and synchronous inductance influenced by stator skewing technique. Based on winding function theory (WFT), the improved method proposes two factors to describe variable inductances along the stator skewing angles. Comprehensive simulations are then performed on three interior permanent magnet synchronous machines (IPMSMs), one normal and two skewed machines (half slot and one slot pitch skewing respectively). Extensive experiments are conducted on relevant prototypes with good correlation. Moreover, analysis and comparisons are made as to the influence of different skewing angles on the inductances and torque-speed curves. It is found that L d increases and L q decreases by skewing, leading to the reduction of the rotor saliency and maximal torque capability, but increase of the flux weakening capability.

Design of a Dual-Stator LTS Vernier Machine for Direct-Drive Wind Power Generation

Conventional low-temperature superconducting (LTS) machines have rather large short-circuit currents, and their peak fault current can reach 15 p.u., which is almost four times that of regular permanent-magnet machines. Vernier machines are well known for their big synchronous inductance, which is useful for reducing the peak current during a short-circuit fault. Moreover, their torque densities are higher compared to conventional synchronous machines due to the magnetic gearing effect. Thus, the purpose of this paper is to introduce a vernier concept to the LTS machine, i.e., a dual-stator vernier LTS machine, which can provide large torque density, as well as small short-circuit current and torque. The proposed machine has two stators and a sandwiched rotor which has spoke-array superconducting magnets. Based on the finite-element analysis, the pole ratio, split ratio, slot opening width, and slot depth of the proposed machine are optimized for a maximum obtainable torque, respectively. Moreover, the short-circuit performances of the LTS vernier machine are investigated and compared to that of a regular LTS machine. It is found that the proposed machine can dramatically reduce the peak current and peak torque during a symmetrical three-phase short-circuit fault, and its rated torque is also higher than that of the regular machine.

MACHINE-TRANSFORMER UNITS FOR WIND TURBINES

Background. Electric generators of wind turbines must meet the following requirements: they must be multi-pole; to have a minimum size and weight; to be non-contact, but controlled; to ensure the maximum possible output voltage when working on the power supply system. Multipole and contactless are relatively simply realized in the synchronous generator with permanent magnet excitation and synchronous inductor generator with electromagnetic excitation; moreover the first one has a disadvantage that there is no possibility to control the output voltage, and the second one has a low magnetic leakage coefficient with the appropriate consequences. Purpose. To compare machine dimensions and weight of the transformer unit with induction generators and is an opportunity to prove their application for systems with low RMS-growth rotation. Methodology. A new design of the electric inductor machine called in technical literature as machine-transformer unit (MTU) is presented. A ratio for estimated capacity determination of such units is obtained. Results. In a specific example it is shown that estimated power of MTU may exceed the same one for traditional synchronous machines at the same dimensions. The MTU design allows placement of stator coil at some distance from the rotating parts of the machine, namely, in a closed container filled with insulating liquid. This will increase capacity by means of more efficient cooling of coil, as well as to increase the output voltage of the MTU as a generator to a level of 35 kV or more. The recommendations on the certain parameters selection of the MTU stator winding are presented. The formulas for copper cost calculating on the MTU field winding and synchronous salient-pole generator are developed. In a specific example it is shown that such costs in synchronous generator exceed 2.5 times the similar ones in the MTU.

Asymmetrical Geometries in Electrical Machines

This paper describes and classifies possibilities of using asymmetric geometry solutions in slotted electrical machines with nonlinear soft magnetic core. These asymmetrical optimizations can reduce cogging torque and torque ripple at the nominal load. Additionally, some of them can improve overload capability, and field weakening capability by proper optimization of over-saturated regions of soft magnetic core. In this paper it is shown that the geometry of the soft magnetic core regions of TC-PMSMs, exhibiting strong saturation due to the interaction of PM- and armature reaction fluxes, has a significant impact on the torque quality. Therefore, by their modifications (including asymmetrical) it is possible to improve the machine characteristics. Two types of PMSM rotor arrangements (embedded-magnet rotor PMSM and rotor-surface magnet PMSM) were simulated with 2D FEM. The results showed that slight modification of the TC-PMSMs soft magnetic regions near by the air gap which exhibit the strongest saturation can lead to significant torque quality variation as well as to synchronous inductance changes.