Method for calculating the resistance of an asynchronous squirrel cage motor according to passport data and estimation of its error

A simpler method is proposed for determining the resistances of an induction motor (total inductive resistance, active resistance of the stator and reduced active resistance of the rotor) according to reference data. Three algebraic equations are obtained from the equations of reactive power dissipation and electromagnetic power in the nominal mode and the equation of electromagnetic power in the critical mode: the first is relative to three resistances, the second is the equation of the dependence of the active resistance of the stator relative to the total inductive resistance, and the third is the active resistance of the rotor relative to the total inductive resistance. An iterative method is proposed for solving this system of equations, which gives a small error already at the second step of the calculations. When assessing the error of the method, the specified values ​​of the electromagnetic power and the multiplicity of the maximum torque were used, which are expressed relative to the reference resistances of the control motors. An estimate is given of the total error from the imperfection of the method and the discrepancy between the reference values ​​of the multiplicity of the maximum torque and power on the motor shaft with their refined values ​​calculated from the resistances from the reference book. Based on the calculated resistances in the nominal mode, the dependences of the active and inductive resistances of the motor are constructed using an accurate and approximate method.

REALIZATION OF TRACTION CAPABILITIES OF A TRACTOR WITH AN ELECTROMECHANICAL POWER TRAIN

A method has been developed to assess the traction capabilities of a tractor with an electromechanical power train and determine the actual speed taking into account three restrictions: on the permissible slip of the tractor, the maximum power of the used internal combustion engine (ICE) and the permissible mode of operation of the traction induction motor (TIM). The developed mathematical model makes it possible to determine the drawbar pull and the actual speed of the tractor when regulating the TIM in the entire operating frequency range of the voltage supplied to the TIM for a comparative assessment of the traction capabilities of the tractor when using different gear ratios of the mechanical part of the power train (MPPT), as well as determine the slip and other parameters of the TIM when it works as a part of the electromechanical power train of the tractor. Calculations show that: 1) if the MPPT ratio is too high, the whole range of tractor operating speeds on the plowing will not be provided, and if the MPPT ratio is too low, the tractor will not be able to develop the maximum possible drawbar pull based on the permissible slip at any voltage frequency from the TIM control range without exceeding the nominal mode of operation of the TIM; 2) the higher the TIM gear ratio, the larger the section of the TIM frequency control range will be, in which the TIM will not be able to develop even the nominal slip due to the restriction on the permissible slip of the tractor, and for the same frequencies in this section, the TIM slip will be more limited at a higher MPPT gear ratio; the lower the transmission ratio of the MPPT, the more the nominal slip of the TIM will be exceeded during acceleration of the tractor with maintaining the maximum possible based on the permissible slip of the thrust force from the minimum speed to the speeds corresponding to plowing.

Conceptual methods of starting and controlling operating modes of compressorless combined cycle gas turbine unit

A method for operation study of a compressorless combined-cycle gas turbine (CCCGT) unit during transients from one steady-state mode to another, including during start-up and shutdown, is proposed. As an example, studies of the transients of an energy complex with a capacity of 60 MW are given. A variant of an algorithm concept for start/stop and transients of such an energy complex is proposed. This concept includes algorithms for starting from the three initial states of the energy complex (cold, hot and standby). For these algorithms, the time and energy consumption characteristics are estimated. It is shown that from a cold state, such an energy complex can be started and brought to the nominal mode in 1.5-2 hours. At the same time, the energy costs will not exceed energy consumption for its own needs in a nominal mode. The start-up time from the hot state can be reduced to 20-25 minutes, and the start-up from the standby state can be 2.5-3 minutes. The proposed concept of control algorithms for transient modes is such, so that a temperature state of the main components and parts of the energy complex is provided at a constant temperature. Thus, the time of transients will be determined only by the speed of the regulatory authorities. Consequently, power systems operating on the CCCGT cycle can operate equally efficiently, both in the basic mode and in the power control mode.

On the Dynamics of a Gravitational Dipole

The main purpose of this paper is to investigate nonlinear oscillations of the gravitational dipole in a neighborhood of its nominal mode. The orbit of the center of mass is assumed to be circular or elliptic with small eccentricity. Consideration is given both to planar and arbitrary spatial deviations of the gravitational dipole from its position corresponding to the nominal mode. The analysis is based on the classical Lyapunov and Poincaré methods and the methods of Kolmogorov – Arnold – Moser (KAM) theory. The necessary calculations are performed using computer algorithms. An analytic representation is given for conditionally periodic oscillations. Special attention is paid to the problem of the existence of periodic motions of the gravitational dipole and their Lyapunov stability, formal stability (stability in an arbitrarily high, but finite, nonlinear approximation) and stability for most (in the sense of Lebesgue measure) initial conditions.

Study of the Influence of the Width and the Pair Shift Of Permanent Magnets on the Torque of an Electric Motor

The article discusses ways to reduce the torque ripple in a permanent magnet motor. With the use of the FEMM program, computational studies were carried out to determine the effect of the width of the magnets and the magnitude of their pairwise angular displacement on ripple in the nominal mode and no-load. The studies were carried out for a sixteen-pole motor with permanent magnets placed on the rotor surface, with a distribut-ed winding on the stator and the number of slots per pole and phase equal to 1. The calculations were per-formed for a rotor with a magnet width in the range of 0.6 - 0.85 p.u. rated torque. It is noted that in the idle mode, the change in the width of the magnets in the specified range and a decrease in the angle of their pair-wise shift makes it possible to reduce the pulsations to a level of 1.3 % of the nominal torque. In the nominal mode, the variation in the width of the magnets and the pairwise angular displacement allows the torque ripple to be reduced to 4.7 %.

EXPERIMENTAL STUDIES OF THE HEATING TEMPERATURE OF THE GREENHOUSE RADIATOR INSTALLATIONS

The thermal regime of plants determines the temperature of the environment, the evaporation of moisture by plants, and the heating of plants by radiation from irradiation plants. Today, induction and LED greenhouse irradiators are promising for replacing irradiators with sodium lamps in terms of energy efficiency. Experimental studies were performed to assess the possibility of proximity of irradiators with induction lamps and LED irradiators to plants to increase their level of irradiation, in comparison with sodium radiation sources. When setting up the experiment, a complex was used, including a Fluke ti32 thermal imager, PHO-250-2-M linear autotransformer, 220V power supply, and a greenhouse irradiator. Processing of the measurement results was carried out in the Fluke SmartView 3.1 program. The heating temperature was determined when reaching the nominal mode, with the nominal mode of operation of the irradiators, with a change in the supply voltage level. Sodium and induction irradiators heat up to a maximum temperature 10 times faster than LED ones. The heating temperature of optical radiation sources with sodium lamps is 5 times higher than LED and 2.5 times higher than induction. A change in the supply voltage level affects the heating temperature of the sodium irradiator with electromagnetic ballasts, the heating temperature of sodium and induction irradiators with electronic ballasts, as well as LED irradiators, remains unchanged and equal to the nominal value at a supply voltage level of ± 10% of Unom.. Low heating temperatures of induction and LED irradiators can reduce the height of their suspension and bring them closer to plants, which will increase the irradiation of plants by increasing the level of illumination or reduce the power of irradiators, that is, increase the energy efficiency of irradiation systems

CONSTRUCTION OF COMPUTER MODEL OF PROPELLER ELECTRIC PLANT BY GENERATOR – MOTOR SYSTEM

This article discusses the creation of a computer model of a single-circuit propeller electric plant. The first step was to construct a mathematical model of the system. On the basis of this model, a computer model was creat-ed in Matlab and was thereafter checked in a nominal mode. Then we verified the model and actual system by conducting an experiment to adjust the frequency of the propeller motor. The results obtained indicate the cor-rectness of the constructed mathematical and computer models and the effectiveness of this system.

Parquetting the Surface of a Parabolic Concentrator of a Solar Photovoltaic Thermal Module According to Given Differential- Geometric Requirements

The article discusses the geometric aspects of the design and creation of parabolic-type solar radiation concentrators. Practical methods of geometric design and manufacturing of concentrators of this kind are presented. Parabolic type concentrator is the main part of the solar photovoltaic thermal installation. Its effectiveness depends on the quality factors of the geometric shaping of the working surface, composed of a set of parquet components, linked to each other on the basis of differential geometric requirements. The distribution of illumination in the focal spot of such a concentrator, made by parquet based on the constructive connection of individual elements, makes it possible to obtain acceptable results. However, there is considerable potential for improving performance by providing a smoother and more uniform illumination of the photodetector. To ensure the specified accuracy and smoothness of the rim of the surface at the stages of designing and manufacturing the device, two methods are proposed: orthogonal and fan-shaped geometric parquetting of the surface of a parabolic concentrator with the ability to pre-set the required shape accuracy for given rim geometrical characteristics. Parquetting with given differential requirements for the surface, in turn, provides for two methods for calculating parquet elements: first, by the minimum number of curvilinear elements followed by stitching, taking into account the differential conditions; the second is based on the maximum number of flat elements, the multiplicity of which provides acceptable smooth surface properties. In this paper, we consider the first method for cases of orthogonal and fan parquet. On the example of a parabolic concentrator, the implementation of the considered method is presented, which provides for the possibility of controlling the geometric smoothness of the concentrator surface in order to ensure optimal distribution of concentrated solar radiation in the focal region. The output characteristics of photovoltaic and thermal converters of solar energy, which are in the focus of such a concentrator, become optimal, and the installation itself will operate in nominal mode.

Formation of energy efficient start-brake modes of the frequency-controlled electric drive in production mechanism

this article the energy efficient frequency way of starting of production mechanisms electrical drive with low power asynchronous motors (from 90 Wt to 5 kWt) is proposed. To provide this With the goal of electrical losses decreasing during asynchronous motor starting the Pontryagin Maximum Principle have been applied by the authors when analysing of two-mass model of production mechanism frequency controlled electrical drive. In result of calculations for frequency controlled electrical drive of production mechanism with 90 Wt power asynchronous motor of the model 4AA50A2 Dependencies of amplitude and frequency of supply voltage by the time are obtained. These dependencies confirm possibility of decreasing the electrical power losses with different values of motor shaft load torques. In compare with the other ways of asynchronous motor starting (for example U/f=const) they allow to decrease the electrical losses more then two times in nominal mode.

A Mistuned Forced Response Analysis of an Embedded Compressor Blisk Using a Reduced-Order Model

Accuracy when assessing mistuned forced response analyses is still a major concern. Since a fully coupled analysis is still very computational expensive, several simplifications and reduced-order models (ROMs) are carried out. The use of a reduction method, the assumptions and simplifications, generate different uncertainties that challenge the accuracy of the results. Experimental data are needed for validation and also to understand the propagation of these uncertainties. This paper shows a detailed mistuned forced response analysis of a compressor blisk. The blisk belongs to the Purdue Three-Stage (P3S) Compressor Research Facility. Two different stator–rotor–stator configurations of 38 and 44 upstream stator vanes are taken into consideration. Several loading conditions are analyzed at three different speed lines. A ROM known as subset nominal mode (SNM), has been used for all the analyses. This reduction takes as a basis a set of modes within a selected frequency spectrum. It can consider a complete family of modes to study the disk–blade modal interaction. A detailed comparison between the predicted and measured results has been performed, showing a good agreement for the high loading (HL) conditions.