Electromotive Force Coefficient Research Articles

Investigation of Analytical Models for Surface-Mounted Permanent Magnet Motor Using Voltage Source Inverter

This article analyzed and compared the complex permeance model (CPM) and nonlinear analytical model (NAM) for surface-mounted permanent magnet (SPM) motor using a voltage source inverter (VSI). For linear CPM, the slotting effect is represented using the improved complex permeance function that describes the real slot shape rather than infinitely deep slot. NAM is extended from CPM and it replaces the magnetic potential drop of stator iron by the equivalent virtual current in the slot-opening and tooth-tip to account for the nonlinearity effect. The nonlinear inductance of SPM motor including the main phase inductance, slot leakage inductance, tooth-tip leakage inductance, and end winding leakage inductance is calculated using the frozen permeability method, which is the key to solve the electric circuit with VSI. The instantaneous back electromotive force (EMF) is calculated from the nonlinear back EMF coefficient and the back EMF neglecting iron nonlinearity. The electromagnetic torque obtained from motor model is used in the mechanical model and then the rotational speed and rotor position are obtained for the electric circuit model. Hence, the iterative solving process for the motor system is established to calculate the transient performance of SPM motor using VSI. Compared with CPM, NAM can greatly improve the calculation accuracy, which is also validated by both finite-element model and experiment. Besides, the proposed NAM is computationally efficient, which is useful for both motor design and motor control.

Development of Inhomogeneity Measurement System for Type T Thermocouple with Local Heating Method

The voltage of thermocouple during process contribution is determined by the absolute thermal electromotive force coefficient in each wire and the temperature difference across the section. This paper described the development of a system as a local heating method for measurements of inhomogeneities in type T thermocouples with various temperature scanning using hot air. The system could control automatically measurement voltage, temperature, distance, and speed of the stepper motor for moving the hot air scanning along with the thermocouple and control with temperature monitoring. Both the measuring and reference junctions were using an ice bath kept at 0 °C. In this paper calculation of interpretation of the measurement results of inhomogeneity using movable heating zone system of type T thermocouples and the system could detected inhomogeneity of thermocouple and there have different characteristics of voltage and seebeck effect.

Determination of modeling parameters for a brushless DC motor that satisfies the power performance of an electric vehicle

The analysis and control of powertrain systems of electric vehicle, which is an important type of new energy vehicle, have been the focus of extensive research, but determining the motor modeling parameters remains a problem. A method of parameter determination for brushless DC motor modeling based on vehicle power performance was developed in this study. The power and torque of the driving motor of an electric vehicle were obtained by using the dynamic equation of the electric vehicle to satisfy the requirements of power performance. The ranges of the back electromotive force coefficient and the winding inductance were derived from the voltage and dynamic equations of brushless DC motor, which were deduced from the expected power and torque of the motor. The modeling parameters were then determined on the basis of the influence of power source voltage, back electromotive force coefficient, winding inductance, and winding resistance on vehicle power performance. A hardware-in-loop simulation of vehicle power performance was performed to verify the effectiveness of the proposed method. Results indicate that the maximum vehicle velocity is 172 km/h, and the acceleration time of 100 km/h is 13 s, which reveal that the motor modeling parameters obtained with the method satisfy relevant requirements.

Thermoelectric properties determination of multilayered semiconductor materials at harmonic single-frequency excitation of temperature field

During several decades, interest in thermal electricity has rose rapidly [1,2]. Thermoelectric devices provide unique abilities and, therefore, are used in assemblies where any other way of direct or invert conversion of heat into electricity is difficult. For example, they are used for thermovisors cooling or combustion engines efficiency increasing [3,4]. The amount of thermal electricity application would significantly increase if thermoelectric converters efficiency will be increased up to 20-30%. The most promising variant of solution for the issue is the search for new materials with maximum possible thermoelectric figure of merit Z [5]. To achieve the high values of the parameter, it is necessary to ensure the lowest thermal conductivity of the material at the highest specific electrical conductivity and thermal electromotive force coefficient of a material. The materials with high Z are constantly searched for, at that, some new pages of material science and thermal electricity are discovered.When new materials are invented, the most important part of that process is produced samples performance tests. Most traditional measuring procedures show intrinsic shortcomings preventing valid data acquisition. Thereupon, we set the goal to develop the technology of accurate and quick measurements for integrated study of thermal and electrophysical qualities of thermoelectric materials. At that, it is supposed that all necessary characteristics of material will be measured simultaneously, the procedure shall be applicable for measurements within the range 100 - 450oK, moreover, for both homogeneous, and segmented branches of thermoelectric generators (TEG).This method is a kind of transient method and one of the easiest. Such methods were introduced as a class by Maldonado [6] for measuring both thermal conductivity and thermoelectric power of bulk materials. The advantages of these technics are good noise immunity, high information content, the ability to conduct experiments with small amplitude of electrical heating current, the independence of the measurement results from the initial temperature distribution and multiple process repeatability [7].At this stage, the initial mathematical model of our method is composed, its verification by means of numerical simulation is conducted, stand model for its experimental check is manufactured, and the first measurements performed.In this work, the principle of operation of the procedure in respect to the measurement of homogeneous sample thermal conductivity.

Nonlinear Model Suitable for the Offline Cosimulation of Fault-Tolerant PM Motors Drives

This paper presents a dynamic model suitable for accurate cosimulation of fault-tolerant permanent-magnet motor drives featuring independent-phase structure. The model is developed in a circuital form where the usual inductive parameters and back electromotive force coefficient are replaced by current and rotor position dependent functions, so that the exact electromagnetic nature and geometry of the machine are accounted over the large flux-current operating range. The model functions are precomputed by a finite element method analysis of a single phase of the machine, once the magnetic independence among the phases has been verified. Then, the circuital model is solved by a dynamical simulator which implements also the drive system, converter, and control, following on the offline cosimulation approach. The proposed model is validated by experiments carried on a fault-tolerant five-phase permanent-magnet motor-drive for aeronautical application, controlled by the brushless dc technique. The results show that the modeling solution is capable to simulate the motor dynamics with a high degree of accuracy, and can be used for an effective rapid prototyping of fault-tolerant drives.

Laser Synthesis of Nanometric Iron Oxide Films with High Seebeck Coefficient and High Thermoelectric Figure of Merit

Radiation of a KrF-laser (λ = 248 nm) was used for the synthesis by reactive pulsed laser deposition (RPLD) of nanometric iron oxide [Fe2O3-X (0≤×≤1)] films with variable thickness, stoichiometry and electrical properties. Film deposition was carried out on <100>Si at its temperature to have being increased from 293 to 800 K. XRD analysis showed that films deposited on Si substrate had polycrystalline structure. Films demonstrated semiconductor temperature trend with variable band gap Eg about 1.0 eV or less depending on oxygen pressure, the number of laser pulses and substrate temperature. Film thickness (13–60 nm) depended on oxygen pressure, substrate temperature and number of laser pulses. The higher substrate temperature, the more crystallinity of the deposited iron oxides’ films was resulting in increasing of thermo electromotive force coefficient (Seebeck coefficient, S). It was found out the optimum oxygen pressure in the reactor, substrate temperature and film thickness when the S coefficient was high as 12–4 mV/K in the range 240–330 K. The thermoelectric figure of merit (ZT) was high as 1–6 in the range 280–330 K. This makes nanometric Fe2O3-X films, synthesized by UV photons using RPLD method, an exceptionally strong candidate for effective thermo sensors and thermo converters operating at moderate temperature.

Laser synthesis of nanometric iron oxide films for thermo-sensing applications

KrF* excimer laser pulses of 248nm were used for the synthesis of nanometric iron oxide films with variable thickness, stoichiometry and electrical properties. Film deposition was carried out on <100> Si and SiO2 substrates. The number of laser pulses was increased from 4000 to 6000, while ambient reactive oxygen pressure varied from 0.1 to 1.0Pa. The film thickness depends on oxygen pressure, number of laser pulses and substrate nature. All films demonstrated semiconducting temperature behaviour with variable band gap (Eg) depending on oxygen pressure, substrate nature and temperature. Eg value was less than 1.0eV for all deposited films. XRD analysis evidenced that films deposited on Si substrate have polycrystalline structure, while films deposited on SiO2 were amorphous. The higher oxygen pressure, the lower crystallinity of the deposited film was observed, resulting in change of thermo electromotive force coefficient (S) value. For larger substrate temperature, a better crystallization was observed in the deposited films, resulting in increased S coefficient value. The largest value of the S coefficient was about 8.7mV/K in the range 290–295K and it decreased to 1.0–1.6mV/K when heating temperature changed from 240 to 330K. The figure of merit of deposited structures was ZT=3–6 in the range 240–330K with a maximum of 12 at 300–304K. We have shown that thermo-sensing characteristics of the films strongly depend on their electrical and structural properties.

Precise Accelerated Torque Control for Small Inductance Brushless DC Motor

In this paper, precise accelerated torque control for a small inductance brushless dc motor (BLDCM) is achieved by electromagnetic torque control and disturbance torque suppression. First, the electromagnetic torque ripple is reduced in commutation and conduction regions. In the former region, the ripple is suppressed by overlapping commutation control and optimizing the duty ratio of the active controller. In the latter region, the unbalance ripple caused by the unbalanced three phase windings is reduced by the proposed asymmetry compensation function, and the disturbance ripple created by the back electromotive force (EMF) is compensated by feedforward control. Second, the disturbance torque has been observed and compensated through the improved disturbance torque controller whose compensation coefficient is obtained by line-to-line back EMF coefficient estimation. And, both the disturbance observation and speed measurement are all synchronized with the encoder pulse alteration. Experimental results are presented to demonstrate the validity and effectiveness of the proposed accelerated torque control scheme.

Stability region analysis of the parasitic loop of the semi-strapdown homing seeker

The stability of the parasitic loop induced by the disturbance rejection effect (DRE) of a semi-strapdown homing seeker (SSHS) is analysed in this paper. First, the seeker’s tracking controller is designed so as to have a simple structure and then the explicit relationships between the control parameters and the desired performance index is presented. Mathematical models of the DRE of the SSHS and the parasitic loop are then proposed. The approximate maximum magnitude of the seeker’s DRE as a function of the friction coefficient and the counter electromotive force coefficient is also given. Routh’s criterion is used to obtain the approximate stability region of the parasitic loop. The necessary and sufficient conditions which ensure the stability of the parasitic loop are directly related to the seeker’s control parameters. This approach provides direct theoretical support for the design of a seeker’s control system. Simulations are performed to verify the validity of the stability analysis performed on the parasitic loop.

Investigation of the thermal electromotive force of steels and alloys of different structural grades in electron beam welding

The results of investigations of the thermoelectric properties of steels of different structural grades and also nickel- and cobalt-based alloys are presented. The temperature dependencies of the absolute thermal electromotive force and the thermal electromotive force coefficient of materials are determined.

The thermodynamic characteristics of point defects and the mechanism of charge transfer in lanthanum cobaltite doped with strontium and nickel

The specific conductivity and thermal electromotive force (EMF) coefficient of lanthanum cobaltite doped with strontium and nickel La0.9Sr0.1Co0.9Ni0.1O3−δ were measured over the temperature and pressure ranges 1023–1223 K and 10−6−1 atm. The oxide was found to exhibit metallic-type conductivity (800 Ω−1 cm−1 ≤ σ ≤ 1150 Ω−1 cm−1) and small positive thermal EMF coefficient values. A joint analysis of the thermodynamic characteristics of formation of point defects and external T and pO2 parameter dependences of conductivity and thermal EMF showed that charge was transferred in the oxide by small-radius polarons according to the hopping mechanism. The role of polarons was played by electrons MeCo′ and holes MeCo• localized on 3d transition metals. The isothermal dependences of the concentrations and mobilities of charge carriers on the degree of oxygen nonstoichiometry of the oxide studied were calculated.

Equilibrium of point defects and charge transfer in lanthanum cobaltite

The specific conductivity logσT and thermal electromotive force coefficient QT of perovskite-like lanthanum cobaltite were measured over the temperature range 1173 K ≤ T ≤ 1323 K depending on the partial pressure of oxygen (10−8 atm ≤ pO2 ≤ 1 atm). The pO2-T-δ phase diagram of solid LaCoO3-δ studied earlier was used to recalculate the electric property data into the log σT-δ and QT-δ dependences. The isoconcentration temperature dependences of specific conductivity (logσ)δ-1/T and Seebeck coefficient Qδ-1/T for LaCoO3-δ were analyzed. The conclusion was drawn that charge transfer was activation in character and had a low activation energy. This was evidence that small-radius polarons (CoCo• and CoCo′) were responsible for charge transfer in perovskite-like lanthanum cobaltite. The calculated equilibrium constants for the formation of electronic defects and functional dependences of defect concentration [CoCo•]T = f1(δ) and [CoCo′]T = f2(δ) were used to analyze polaron transfer parameters in LaCoO3-δ.