Research of current distribution by phases in asynchronous electric motor with a combined winding

THE PURPOSE. The asynchronous electric motor with a squirrel cage rotor is widely used in the electric driven industry and agricultural machinery. One of the possible ways to improve its energy characteristics is to use a combined 12-zone stator winding instead of the standard 6-zone one. However, in a combined winding with a parallel connection of the «star» and «delta» phases, the phases may not be loaded equally. Therefore, the main purpose of the work under analysis is to study the distribution of currents between the phases of the «star» and «delta» in the asynchronous motor with a combined winding.METHODS. The study was performed on the AIR71V4 engine, rewound onto a combined winding, in which the real ratio of the active resistances of the «delta» and «star» turned out to be 7% less than the theoretical one. The tests were carried out in no-load and short-circuit mode when powered from a three-phase network, as well as in short-circuit mode when one of the line wires is broken.RESULTS. The work gives the values of the currents flowing through the phases of the combined winding. For the experimental sample, the deviation of the obtained currents from the theoretical values is determined. Equations of currents are obtained when one of the linear wires is broken. Schemes for switching on the main contacts of a thermal relay for a motor with a combined winding are proposed.CONCLUSION. The results of the study showed that in an asynchronous motor with a combined winding, in which the real ratio of the active resistances of the «delta» and «star» is less than the theoretical one, the current is not proportionally distributed over the phases. The most preferred circuit for switching on a thermal relay is one in which its main contacts are connected to the «delta» phases, and the thermal relay must be three-pole.

Development of a methodology for calculating and designing a single-phase asynchronous electric motor without external phase-shifting devices for ship automation systems using a mathematical model obtained using experimental planning methods

Статья посвящена разработке методики проектирования однофазного асинхронного электродвигателя без внешних фазосдвигающих устройств для систем судовой автоматики. Отмечается, что существующие на сегодняшний день известные методики расчёта микромашин не учитывает потерь в стали, что приводит к значительным погрешностям при расчёте двигателя. Авторами предлагается применять разработанную уточненную методику расчёта двигателя для дальнейшего его проектирования. Отмечается, что из выявленных в работе зависимостей важнейшей является зависимость пускового момента от электрического угла между осями обмоток 1 и 44 - α. Где выбор не оптимального электрического угла - крайне негативно сказывается на величине пускового момента однофазной микромашины. Для пояснения особенностей определения активной части двигателя авторами строится график зависимости наружной поверхности и потерь от полезной мощности. Также, в статье авторы приводят номограммы, позволяющие принимать проектировочные решения не только на основания расчёта, но и графоаналитическим методом. Результатом работы является получение новой методики расчёта и проектирования однофазной микромашины для систем судовой автоматики, используя для расчёт математическую модель, полученную с помощью методов планирования эксперимента. The article is devoted to the development of a design technique for a single-phase asynchronous electric motor without external phase-shifting devices for ship automation systems. It is noted that the currently known methods for calculating micromachines do not take into account losses in steel, which leads to significant errors in calculating the engine. The authors propose to apply the developed refined methodology for calculating the engine for its further design. It is noted that of the dependences identified in the work, the most important is the dependence of the starting torque on the electric angle between the axes of the windings 1 and 44 - α. Where the choice of a non-optimal electrical angle has an extremely negative effect on the magnitude of the starting torque of a single-phase micromachine. To clarify the features of determining the active part of the engine, the authors build a graph of the dependence of the outer surface and losses on the net power. Also, in the article, the authors provide nomograms that allow making design decisions not only on the basis of calculation, but also by the graphical analytical method. The result of the work is to obtain a new methodology for calculating and designing a single-phase micromachine for ship automation systems, using for the calculation a mathematical model obtained using experimental planning methods.

Power Plant for a 0.6­0.8 Class Mobile Vehicle Based on the T­16 Self­Propelled Tractor Chassis

The authors showed the necessity to develop a rear-wheel drive hybrid mobile agricultural vehicle with electric drive and power plant. (Research purpose) To develop and study a new kinematic scheme of a mobile vehicle based on a self-propelled tractor T-16 chassis, which provides increased reliability, comfortable working conditions for the operator, a significant improvement in the environmental situation, and better economic efficiency. (Materials and methods) The authors listed the advantages of the new hybrid vehicle kinematic scheme. They gave the comparative technical characteristics of a diesel engine and an asynchronous electric motor. They developed a new methodology for calculating gas turbine engine technical parameters and described the production process of an electric drive with a capacity of 11 kilowatts to drive the driving wheels. The authors gave a thermal design of the compressor parameters, turbine. They calculated the excess air ratio. According to the parameters obtained, a K27-145 turbocharger was chosen, which simultaneously served as a turbine and a compressor of a gas turbine engine. A kinematic diagram was created with a gas turbine electric generator, storage batteries, an asynchronous frequency-controlled motor and a mechanical gearbox. (Results and discussion) The authors proposed to use a mobile vehicle as a mobile power plant: an output socket with a voltage of 220-230 volts operated from an inverter connected to batteries; the second socket – with a three-phase voltage of 400 volts – from the generator of the power gas turbine plant. (Conclusions) It was proved that the proposed hybrid mobile vehicle design on a battery and a gas turbine was capable of operating throughout the entire working day, and to provide 16 horsepower of a diesel engine, it was enough to install an asynchronous electric motor with a capacity of 7.5 kilowatts. The authors calculated the compressor performance of the gas turbine engine, which was 0.178 kilograms per second. The geometric parameters of the combustion chamber and the technical characteristics of the turbocharger were determined.

ANALYSIS OF THE OPERATING MODES OF THE SUSPENDED CABLE CAR ELECTRIC DRIVE USING THE VECTOR CONTROL SYSTEM

Continuous transport systems, including rope conveyors designed to move people and goods, are subject to very strict safety and energy efficiency requirements. As a rule, suspended cableways in operation have an unregulated electric drive with a smooth start system. Among the ways to meet these requirements is the use of modern regulated electric drives. The electromechanical system with a vector-controlled asynchronous electric motor is considered in the work. Based on the obtained model, within the framework of the MATLAB / Simulink application package, an investigation of the dynamic characteristics of the cableway electric drive was carried out. An analysis of the nature of the distribution of dynamic error in terms of speed and energy losses depending on the load and speed of movement of the rope traction element of the transport system is given. The results presented in the article make it possible to choose rational electric drives for continuous transport systems with rope traction elements. References 5, figures 5, table.

Fuzzy case models for project management using a multi-ontology approach

The article identifies the features of innovative projects that should be taken into account when building models of information processes in decision support systems (DSS) for project management. It is shown that, in terms of taking into account these features, methods for forming knowledge in the form of ontologies and the use of information analysis procedures based on precedent methods seem to be promising. The limitations of existing precedent methods, including those involving the formation of a knowledge base in the form of ontologies for their use in project management, are revealed. Development trends in methods for representing knowledge in the form of ontologies and their use within the framework of precedent approaches are substantiated. The trends are as follows: providing the ability to use several independent ontologies for different subject areas; taking into account the differences of the analyzed projects and creating conditions for the adaptation of ontologies when the indicators of the external and internal environments of the project change. A DSS structure for project management is proposed, which provides the use of several subject and functional ontologies and a developed fuzzy logic algorithm for adapting earlier rational decisions to the current situation. Software tools implementing the proposed models and procedures are described, as well as the results of their application to decision support in managing a project to develop an innovative asynchronous electric motor. It is shown that the proposed approach allows the description of the current situation in a linguistic form. At the same time, in contrast to the known variants of precedent methods based on the use of ontological models, the described algorithm for deriving solutions allows taking into account the characteristics of the analyzed situations related to various subject and functional areas. This allows you to develop recommendations for the allocation of resources for the implementation of design work based on the analysis of positive experience in the implementation of projects of various sizes.

Experimental study of the VFD’s speed stabilization efficiency under torque disturbances

The article presents a technique for experimental research of variable frequency drives experiencing periodic torque disturbances of variable frequency. The technique is based on the nonlinear transfer function of a link of an asynchronous electric motor, which forms an electromagnetic torque, proposed in previously published articles. The dependence of the transfer function on the frequency of the stator voltage and slip determines the research methodology. Experiments have shown the advantage of the dynamic characteristics of a drive with a positive feedback on the stator current over electric drives with traditional control methods (vector and scalar sensorless), and in terms of dynamic characteristics they also exceed drives with a vector control closed in motor speed. These advantages are retained when the frequency of change of the disturbing torque is changed from 0 to 5 Hz.

Comparison of Energy Indicators of the Electric Lift Drive of the Ekg-5 Excavator with Different Power Converters

The energy indicators of the EKG-5 excavator lifting electric drive with thyristor power circuits have been determined according to the systems thyristor direct frequency converter - two-phase asynchronous electric motor, converter-DC motor and direct frequency converter - three-phase asynchronous electric motor. Losses in electric motors and converters have been determined, taking into account the specifics of their joint work in theefficiency for the excavation cycle were determined based on the results of calculating the simulation model, the initial data for which were the parameters of the excavation cycle of the lift drive of a real excavator. Distortion coefficients of the mains current were determined for two cases: during digging and during accelerated lowering of an empty bucket. For comparison, the energy indicators of the selected electric drives with a filter-compensating device were calculated. The analysis of energy indicators is made.

AUTOMATIC CONTROL OF GRAIN COMBINE HARVESTER CLEANING OPERATION

The technological indices of the efficiency of grain combine harvesteroperation include the quality of the ob-tained grain mixture and the amount of grain loss. The hu-man factor has a great influence on these indices which can be minimized by automating the control of the combine harvestercleaning. We have proposed a design of such a device including a fan drive from an asynchronous electric motor with afrequency converter, servo controls for adjust-ing the angles of the upper and lower shutters, an acoustic grain loss sensor that allows feedback in the control sys-tem and the process controller. As a result, the effect of the internal combustion engine ofthe combine on the shaft rotation frequency will be reduced; there will be no need to use the DC electric drive or a fan mechanical drive; it will be possible to automatically adjust the angle of inclination of the shutters with an accuracy of 0.1°; therewill be the possibility of constructing a cleaning system control algo-rithm based on neural networks. The use of this device will improve the quality of harvesting, reduce grain losses and reduce the amount of impurities in the combine hopper

Analysis of the operating parameters in a Stirling cryocooler

In this work, the results obtained in different tests performed on a Stirling cryocooler are shows, as well as a comparative analysis of these results with different load pressures. The prototype is a single-acting Stirling engine with a piston and displacer, which is used to liquefy air with helium as the working fluid; this is an integral Stirling (β-type). A three-phase asynchronous electric motor drives the Stirling engine and cooling, in the hot focus, is performed with a pressurized water circuit. In the cold focus are reached very low temperatures, around 75 K (-198 °C). The study has been developed at different load pressures of the working fluid and it shows a comparative analysis about the most important work parameters evolution. The parameters studied are the following: cooling water inlet and outlet temperatures, cold and hot focus temperatures, voltage and intensity consumed by the electric motor that drives the Stirling engine and quantity of liquid air obtained. The results show that it is very likely to use this configuration in industrial processes when they need cold and heat simultaneously.