Optimum design of high-speed single-phase flux reversal motor with reduced torque ripple

Single-phase motors are used in low-power, cost-effective, variable-speed applications. As a replacement to traditional single-phase synchronous motors with magnets on the rotor, single-phase flux reversal motors (FRMs) with a rugged and reliable toothed rotor are considered for the high-speed applications. However, torque pulsations of single-phase motors are high. The aim of this work is to minimize the torque ripple and increase its minimum instantaneous value, as well as to reduce FRM losses. To solve this problem, an asymmetric rotor is used, and an objective function is proposed, which includes parameters characterizing the pulsations of the torque and the loss of FRM for two load conditions. To optimize the single-phase FRM and minimize the objective function, the Nelder-Mead method was applied. The optimization criterion was selected to maximize the efficiency, to reduce the torque ripple, and to the avoid the negative torque in a wide range of powers at the fan load (quadric dependence of torque on speed). Two operating loading modes are considered. After two stages of optimization, the peak-to-peak torque ripple in the FRM in the rated loading mode decreased by 1.7 times, and in the mode with reduced load by 2.7 times. In addition, in the FRM before optimization, the torque has sections with negative values, and in the FRM after optimization, the torque is positive over the entire period. Although losses in the rated mode increased by 4%, when underloaded, they decreased by 11%, which creates an additional advantage for applications that work most of the time with underload. © 2020 by the authors.Ministry of Science and Higher Education of the Russian Federation: FEUZ-2020-0060The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, Project No. FEUZ-2020-0060). The authors thank the editors and reviewers for careful reading, and constructive comments

Life cycle energy cost assessment for pump units with various types of line-start operating motors including cable losses

The paper presents a comparative analysis of life-cycle energy consumption for three different types of 4 kW line-start motors used in a pump unit with throttling: the most widely used induction motor with IE3 efficiency class, line start permanent magnet synchronous motor with IE4 efficiency class and line start synchronous reluctance motor with IE4 efficiency class. The operating cycle for pump units with constant flow is considered for the above-mentioned types of motors taking into account not only the losses in the pump and motor, but also in the power supply cable. It is shown that the line start synchronous reluctance motor without magnets has the highest efficiency over the entire considered loading range. However, its power factor is lower than that of the synchronous motor with magnets and therefore it has more significant losses in power supply cable. Despite this disadvantage, the line-start reluctance motor is a good alternative to widespread induction motor since it allows saving of approximately 4000 euro more than the latter during the 20 years life cycle. It also provides similar savings in comparison to the permanent magnet synchronous motor, but unlike it, it does not have costly rare-earth materials in the rotor. © 2020 by the authors

Obtaining cyclopentanone from acidic wastewater of caprolactam production

It has been shown that adipic acid released from the by-products of caprolactam production is a promising raw material for the production of cyclopentanone. The thermal stability of calcium adipate was investigated by the derivatographic method and the conditions were selected that ensure the yield of at least 50% of the target cyclopentanone with a purity of at least 99%

Stress-strain state and stability of composite sandwich shells with a scaling zone between the core and facings

A finite element model is presented for analysing the strength and stability of sandwich shells of arbitrary configuration with an adhesion failure zone between the core and one of the facings. The model is based on the following assumptions: both facings are laminated Timoshenko-type composite shells; in the core only transverse shear stresses and normal stresses in the thickness direction have non-zero values; in the adhesion failure zone a free slip in the tangential plane, and a unilateral contact along the normal are possible; in the stability problem the prebuckling state is assumed to be linear. Displacements and rotation angles of the normals towards the facings, as well as stresses in the core are taken as global degrees of freedom. The algebraic problem is solved by using a special step-by-step procedure of determining the contract area in the scaling zone and employing unilateral restrictions to some of the unknowns. Numerical examples are also given

Numerical analysis method for studying local forms of stability loss of bearing layers of three-layered shells using mixed forms

A revised formulation of linearized stability problems of three-layered shells with a sofi filler has been presented. The form of stability loss of the rigid layers is mixed in the shells when the moment precritical stress-strain state (SSS) is reached and is localized in the principal moment SSS zones. If the filler thickness is much greater than the thickness of the rigid layers, the size of the bulges and thickness of the filler have the same order of magnitude. Thus, a very fine grid must be used for a numerical solution of the stability loss equations, which poses considerable computational difficulties. A numerical analysis method is proposed for the local forms of mixed mode stability loss of the rigid layers of a three-layered shell. Using this method, the solution of equations for the precritical SSS by the finite element scheme is found but an analytical solution of reduced stability loss equations is presented for estimating the critical load. This solution is an asymptotic approximation for local modes of stability loss implemented into design. © 1995 Plenum Publishing Corporation

Stress analysis of helicopter main rotor torsion bar

The results of stress analysis for the main rotor torsion bar of the ANSAT helicopter based on the finite element method are presented. The analysis was performed for the base types of loading in the linear statement. The analysis results agree well with the experimental data. © Allerton Press, Inc., 2009

Stress-strain state and stability of composite sandwich shells with a scaling zone between the core and facings

A finite element model is presented for analyzing the strength and stability of sandwich shells of arbitrary configuration with an adhesion failure zone between the core and one of the facings. The model is based on the assumptions that both facings are laminated Timoshenko-type composite shells, only transverse shear stresses in the core and normal stresses in the thickness direction have nonzero values, a free slip in the tangential plane in the adhesion failure zone and unilateral contact along the normal are possible, and the prebuckling state in the stability problem is linear. Biquadratic nine-node approximations for all functions and numerical integration were used. The displacements and rotation angles of the normals toward the facings as well as stresses in the core are taken as global degrees of freedom. The algebraic problem is solved using a special step-by-step procedure of determining the contact area in the scaling zone and employing unilateral constraints for some of the unknowns. Numerical examples are also given. © 1994 Plenum Publishing Corporation

Feasibility study of pump units with various direct-on-line electric motors considering cable and transformer losses

The high energy intensity of the modern industry determines the high urgency of increasing the energy efficiency of production processes. However, a big number of motor types of enhanced efficiency classes are available on the market. The motor users can be confused about the choice of the right motor solution for a certain application. In this paper, to help with this choice the energy efficiency indicators of various types of electric motors in a low-power pump unit with a constant rotation speed are studied. Moreover, not only power losses in the motor are considered, but also power losses in the cable and transformer, which are influenced by the power factor of the motor. Induction motors (IMs) and synchronous motors powered directly from the grid (direct-on-line synchronous motor with permanent magnet in the rotor, DOL PMSM; direct-on-line synchronous reluctance motor without permanent magnet, DOL SynRM) of IE2, IE3, and IE4 energy efficiency classes are compared. To carry out the analysis, polynomial interpolation of the available catalogue data and experimental data of the motors are used. The main criteria for comparing different motors in this work are the energy savings over the pump’s life cycle and the payback period when replacing an IE2 motor with a motor of a higher energy efficiency class. The article shows that although the DOL PMSM has a lower motor efficiency than the DOL SynRM, it saves more energy due to its higher power factor, which reduces cable and transformer losses. It is also shown that, despite the highest initial cost, when taking into account cable and transformer losses, the payback period of DOL PMSM can be shorter than that of IE3 and IE4 induction motors. DOL SynRM has the shortest payback period in all considered cases, has no troublesome rare-earth permanent magnets, and can also be a valuable solution. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.The work was partially supported by the Ministry of Science and Higher Education of the Russian Federation (through the basic part of the government mandate, Project No. FEUZ 2020-0060)

Design and Mathematical Modeling of Gearless SMC Flux Reversal Motor

This paper considers the design of a three-phase gearless flux reversal machine (FRM) with permanent magnets (PM) mounted on the stator. Its stator magnetic core is made of a solid soft magnetic composite material (SMC) with a slot for laying the winding in the middle. 48 magnetic poles are located on the surface of each stator tooth, while the rotor has 24 teeth. This paper describes the mathematical model and the results of the performance calculation of the three-phase SMC FRM operating in motoring mode. Finally, comparison of the SMC FRM with the characteristics of the conventional surface mounted permanent magnet machine (SM-PMSM) made of laminated steel is performed. For fair comparison, both the SMC FRM and SM-PMSM have the same outer stator diameter and approximately the same volume. © 2018 IEEE

SOME UNUSUAL SOLUTIONS FOR EUROPEAN NETWORKS

Authors present several non-conventional solutions unused in Europe which are, however, frequently adopted in some medium (M) and low (L) voltages (V) networks from North-American and Australian countries, especially in low density areas of consumption in rural and urban distribution. The proposed solutions may assure diversified supply possibilities in our middle and South–Eastern regions, as regards modernizing and upgrading the distribution networks. The solutions try to propose to adapt our European practice to the North-American experience, aiming at developing more flexible, cheaper and safer supply of the consumers, both at MV and at LV networks. Several original solutions promoted in Romanian networks and their peculiarities are also described. The paper presents distribution schemes at medium voltage in connection with low voltage supply in different condition of neutral treatment at MV or LV. It also shows the measures to be adopted in order to diminish the investment expenses in low voltage at the supplied consumers. The technical condition of co-existence of OHEL at MV and LV on the same poles, without jeopardizing the LV equipment, is necessary. Among the solutions proposed, the authors also describe the unconventional one, consisting in the supply of isolated monophase consumer at MV by ground return and also the conditions necessary for sure and safe operation of this particularly connection. Finally, there are shown some conclusions about the necessity to assure imposed environmental conditions