Economic design of sleeve rotor induction motor using rotor ends

<span>In this paper, the field analysis of the sleeve rotor induction motor (IM) is carried out taking the rotor ends into consideration. Here, the field system equations are derived using the cylindrical model with applying Maxwell's field equations. It is expected that, both starting and maximum torques will increase with taking the rotor ends than that without rotor ends. A simple model is used to establish the geometry of the rotor ends current density and to investigate the air gap flux density. The magnetic flux is assumed to remain radially constant through the very small air gap length between the sleeve and stator surfaces. Variation of the field in the radial direction is ignored and the skin effect in the axial direction is considered. The axial distributions of the air gap flux density, the sleeve current density components and the force density have been determined. The motor performance is carried out taking into account the effects of the rotor ends on the starting and normal operations. The sleeve rotor resistance and leakage reactance have been obtained in terms of the cylindrical geometry of the machine. These equivalent circuit parameters have been calculated and plotted as functions of the motor speed with and without the rotor ends.</span>

Experimental Study on Creep of Sandstone under Hydrochemical Corrosion

Corrosion creep of sandstone has great influence on the safety and stability of geotechnical engineering, and it is of great significance to study the creep characteristics of sandstone under the action of hydrochemical corrosion for the long-term stability of geotechnical engineering. Through creep test of corroded rock, the characteristics of rock deformation and strength are analyzed. Combined with electrochemical impedance spectroscopy (EIS), the microcracks of corroded sandstone during creep process are detected, and the variation law of equivalent circuit parameters and the development trend of microcracks during creep process of corroded sandstone are analyzed. The test results show that the creep characteristics of rock samples are related to the hydrochemical environment; The medium-and long-term strength of the solution with high pH value is relatively small, and the difference with uniaxial compressive strength is large; Moreover, there is a certain correlation between creep of rock samples and equivalent circuit parameters. In this paper, the influence of creep deformation, mechanical properties and hydrochemical environment on sandstone creep is analyzed, and the research results can provide reference for stability analysis of related geotechnical engineering.

FE-Aided Synchronization Analysis of Line-Start Synchronous Reluctance Motors

Since line-start synchronous permanent magnet motors (LSPMs) entered the market, they have attracted research interest toward counterpart induction motors of low power-ratings. This paper reports an investigation of line-start synchronous reluctance motors (LS-SynRMs). LS-SynRMs has not been investigated as much as LSPMs have. A motor needs to maximize rotor saliency to achieve high efficiency and a high power-factor. This results in complicated rotor geometry because the rotor cage and multiple flux barriers share the same rotor space. This paper provides an approximate method based on steady state torque analysis by which to estimate the critical inertia of a LS-SynRM. A finite element analysis (FEA)-aided analytical approach to the approximation of steady state torque is proposed to replace the more typical approach based on equivalent circuit parameters. The critical inertia resulting from the proposed method is compared to the results obtained using the FEA.

Estimation of the Equivalent Circuit Parameters of Induction Motors by Laboratory Test

The determination of equivalent circuit parameters for AC induction motors represents an important task in an electrical machine laboratory. Frequently used open-circuit and short current tests answer these requirements. However, the results have a low accuracy. This becomes especially obvious when the equivalent circuit is applied for the motor current and power prediction. The main obstacles in this circumstance lie in the difficulty of providing a pristine open-circuit test, the lack of which causes errors in parameter estimation. A much more accurate approach can be carried out with a test including several output points with measurements of the motor torque, velocity, current, and power magnitudes. Nevertheless, a relatively simple and accurate method to ensure determining parameters for such tests does not exist. This article tries to provide such a method by an approach based on Kloss’s simplified equation and the Thevenin theorem. The significant novelty of the method is the specially selected synergetic interaction between the analytical and numerical approaches, which give a relatively simple algorithm with a good accuracy and a convergence of the parameters’ estimation.

A Deterioration Diagnosis Circuit of a Lithium-Ion Battery Using Microcomputer Implementing Z-Transform Convolution

The deterioration of lithium-ion batteries has been detected by an increase in the battery impedance by means of an alternating current method or a battery capacity test. These methods require an interruption of the operation because the battery has to be removed. A method estimating equivalent circuit parameters of a lithium-ion battery during operation is proposed in this article. The increase in the internal impedance has a close relation to the deterioration of the battery. The circuit is expressed by a resister and an RC parallel circuit connected in series. The parameters can be estimated by applying a convolution technique to the voltage and current fluctuation of the battery during operation. A diagnosis circuit using a microcomputer is developed using a simple algorithm employing z-transformation in the parameter estimation. The estimated parameters depend on its state of charge (SOC) and ambient temperature. The SOC dependency is solved by estimating timing, and the temperature dependency is corrected by a function derived in this article. The deterioration diagnosis of the battery can be applied to a solar power generation system, and the feasibility is discussed in this article.