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1
Content available remote Five-Phase Squirrel-Cage Motor : Construction and Drive Properties
EN
This paper presents the simulation and experimental results of a five-phase squirrel-cage induction motor. The new machine has been designed to operate in a drive system with third harmonic rotor flux injection in order to improve the motor torque utilization. The motor structure, the mathematical model as well as the laboratory prototype have been described. The motor speed-torque characteristics and transients are elaborated on. Furthermore, the start-up possibility in the case of one or two stator winding faults has been shown as well. The idea of a closed loop speed control with increased load torque is presented.
PL
W pracy przedstawiono 5-fazowy silnik indukcyjny klatkowy, który został zaprojektowan tak, aby wykorzystać wyższe harmoniczne momentu elektromagnrtycznego. Przedstawiono konstrukcję maszyny, model matematyczny oraz zbudowany prototyp laboratoryjny. Zaprezentowano charakterystyki mechaniczne oraz przebiegi w stanach przejściowych. Wskazano na możliwość rozruchu i pracy maszyny przy uszkodzeniu jednej lub dwóch faz. Przedstawiono koncepcję sterowania ze zwiększeniem momentu napędowego.
2
Content available remote Wirnik klatkowy z rozruchowymi zwojami zwartymi
PL
O trwałości silnika klatkowego dużej mocy, przewidzianego do trudnych warunków rozruchowych decyduje rozwiązanie wirnika. Najbardziej odpornym na działanie prądu rozruchowego jest wirnik z tzw. prętami biernymi. Rozwiązanie to ma jednak swoje mankamenty: pręty bierne o dużej masie zajmująznaczną objętość w czynnej części silnika. W rozwiązaniu opisanym w artykule, rolę prętów biernych spełniają zwoje zwarte rozmieszczone pojedynczo, w każdym żłobku wirnika. Ich masa może być znacząco mniejsza od masy litych prętów. Ponadto reluktancja obwodu magnetycznego strumienia rozproszenia żłobkowego w wirniku z rozruchowymi zwojami zwartymi jest znacznie mniejsza; skutkuje to zmniejszeniem wielkości prądu rozruchowego silnika.
EN
Exploitation durability of the squirrel cage motor at heavy starting conditions depends on their rotor design. The most reliable induction motor for frequently repeated or long lasting starts is that with idle bars in the rotor. But idle bars design has their disadvantages as well. The idle bars should be massive, they take a pretty large volume of the active part of the rot or. In the paper a special rotor design, with short circuited turns in the slots, instead of massive bars is presented. Laboratory test results of an experimental squirrel cage 90 kW motor with short circuited turns in their rotor are given. The motor was designed, manufactured and tested at KOMEL Institute, Katowice.
PL
W pracy przedstawiono metodę analizy cieplnej silnika indukcyjnego klatkowego. Model termiczny analizowanego silnika został zbudowany na podstawie metody schematów cieplnych i zaimplementowany środowisku MATLAB/SIMULINK przy wykorzystaniu dodatkowego toolboxa PLECS. Za pomocą zbudowanego modelu można w stosunkowo łatwy sposób wyznaczyć przyrosty temperatury w poszczególnych elementach silnika, a zwłaszcza w części połączeń czołowych oraz części żłobkowej uzwojenia. Wielkości te są niezmiernie ważne podczas projektowania jak i eksploatacji maszyn elektrycznych. Otrzymane wyniki z symulacji zostały zweryfikowane pomiarami wykonanymi na modelu fizycznym silnika.
EN
The article describes a method of thermal calculations of squirrel cage induction motor. Thermal model of the analysed motor was built on the basis of on the thermal network method and was implemented in MATLAB/SIMULINK environment by using an optional toolbox PLECS. A thermal model of a motor presented in the paper allows to determine temperatures of particular components of the machine, especially in end winding and slot part of the winding. Hence thermal phenomena which occur in electric motors are an important aspects while designing them and in their exploitation. Simulation results, which had been obtained, were verified by measurements performed on the physical model of the motor. Temperature measurements were made with support of the environment Lab View and controller NI PXIe-8130 with card NI PXI-4353.
EN
Energy-efficient industrial drives and control systems are designed to minimize power consumption. Energy consumption is associated with the efficiency of energy conversion in electric motors. In the paper the in-service efficiency estimation method for induction cage motor was shown. The implementation of the method was based on the air-gap torque method. The results were compared with those obtained with the known air-gap torque method. The authors present a significant impact of estimation of mechanical power losses and stray load losses in the motor on the accuracy of estimating the coefficient of efficiency cage induction motor.
EN
High speed squirrel-cage motors are a relatively unknown group of machines, mainly due to their particular application. High rotational speed is achieved by supplying the motors with 400-1500Hz frequency voltage. Their operation in special conditions results in the fact that their structure and some properties differ from those of squirrel-cage induction machines supplied with 50Hz frequency voltage. The use of closed rotor slots causes strong saturation of the magnetic circuit for the slot leakage flux. Changes in the current in the slot causes a varying state of saturation and thus rotor leakage inductance is not a constant parameter. When determining the rotor winding leakage inductance for classic induction motors supplied with 50Hz frequency voltage, the influence of the saturation of the magnetic circuit for the leakage flux is usually omitted. This is a standard approach and an equivalent scheme, mentioned in literature, is used in such a case. Identification of the inductance in motors supplied with high frequency voltage, in which the phenomenon of core saturation occurs, is a relatively complex issue due to the complicated distribution of magnetic flux, and especially the leakage flux. The value of leakage inductance was determined experimentally. The paper presents differential equations describing a mathematical model and transients of the current and electromagnetic torque, obtained by simulating the start-up of a squirrel-cage high-speed motor.
EN
Economic effectiveness of the operation of a propulsion system depends on energy indices of motors. Along with the type of operation, the load can vary greatly. Most induction motors operate at load which is considerably lower than their nominal load. Operation at small load or idle run has an adverse effect, when energy indices of the motor, such as power factor and energy efficiency, are very low. There is a need to improve these indices and establish conditions for optimum motor operation. If the motor's load is lower than its nominal load, supply voltage should be lowered to make the energy indices as high as possible. Thus, supplying the motor with voltage which varies depending on the degree of load brings positive results. At nominal load, the motor must by supplied with nominal voltage, however, as the load decreases, the voltage should be accordingly lowered. Lowering the supply voltage will result in decreased energy losses, which are connected with it, as well as increased energy efficiency and power factor. This leads to lower power consumption and thus to saving electric energy. The paper presents transients of current supplied from the mains, the power factor, and motor energy efficiency for various degrees of voltage changes ensuring the motor,s low-energy operation.
EN
Energy-saving control system of pump drive are designed to minimize power consumption. Energy consumption in pump units depends on the instantaneous efficiency of the pump and motor. The paper was presented non-invasive method for determining the coefficient of efficiency induction-cage motor fed from a source with adjustable frequency. The method has been implemented through the method of determining air gap torque in the motor. Proposes a new method of determining the mechanical losses in the induction-cage motor. Influence of the mechanical power loss estimating on the motor efficiency determining was presented. The article presented the results of laboratory tests and simulations.
EN
Industrial AC cage rotor motors of nominal voltage 6000 and 10 000V are usually started by switching direct on line. Many failures of the motors is often the result of their design which do not take into account the thermal and mechanical stresses caused by initial starting current surges in stator and rotor (squirrel cage) windings, as well as electro-dynamic vibrations occurred at starting period. Proper choice and proper design of the rotor cage is of high importance for d.o.l. started induction motors of middle and high capacity. In the paper thermal and dynamic effects of starting current of d.o.l. started motors are evaluated, same examples of typical disintegrated squirrel cages showed and recommendations for motor’s exploitation given.
9
Content available remote Napęd pojazdu elektrycznego z silnikiem asynchronicznym klatkowym
PL
W artykule przedstawiono układ napędowy pojazdu elektrycznego wykorzystujący niezawodny i tani silnik prądu przemiennego. Zastosowany trójfazowy silnik asynchroniczny klatkowy wymaga zasilania z falownika napięcia przekształcającego napięcie stałe z akumulatorów na napięcie przemienne. Wykonany tranzystorowy przekształtnik sterowany jest mikroprocesorowo. Zastosowany procesor realizuje algorytm sterowania polowo zorientowanego, kontrolując moment i strumień silnika. Napęd nie wymaga instalowania czujnika prędkości obrotowej silnika. Prędkość silnika wykorzystywana w procesie sterowania jest obliczana przez procesor. Rozwiązanie przewidziane jest do zastosowania w napędzie bagażowego wózka transportowego, zastępując poprzednio istniejące rozwiązanie z silnikiem szeregowym prądu stałego. Zarówno silnik, jak i przekształtnik zostały specjalnie zaprojektowane i wykonane do realizacji układu napędowego. W artykule przedstawiono opis zrealizowanego układu, algorytmów sterowania i obliczania prędkości oraz wyniki badań napędu.
EN
The article presents electric vehicle firm power transmission system using reliable and cheap alternating-current motor. Applied three-phase asynchronous squirrel-cage motor is powered from voltage inverter converting battery direct current voltage into alternating voltage. Power electronic converter is controlled by microprocessor. The processor operates according to field oriented control algorithm controlling motor torque and flux. The drive does not require motor speed sensor to be installed. Motor speed, used by the control process, is calculated by the processor. This construction is designed for battery-electric truck drive replacing previous solution using direct-current series motor. Both motor and inverter were custom designed and manufactured for this power transmission system. The article presents the system description, control and speed calculation algorithms as well as drive testing results.
10
EN
This article presents considerations on the condition of the occurrence of maximum efficiency in the three-phase induction motor supplied by a constant voltage value. A relationship was derived, which allows to calculate with great accuracy the location of maximum efficiency. Comparison of laboratory results with the results of efficiency calculations confirmed the possibility of analytical determination of the output power for maximum efficiency. A general condition for the occurrence of maximum efficiency was formulated, which speaks about the approximate equality of no-load losses and losses in the windings of the rotor current. Calculation tests performed for the two groups losses for maximum efficiency point confirmed the general condition of maximum efficiency. Laboratory studies were conducted using the squirrel-cage motor with rated power PN = 1.1 kW and rated speed nN = 1415 rpm.
EN
This paper deals with influence of voltage interharmonics on currents in an induction cage machine. The results of investigations are presented for 5,5 kW four-pole induction cage machine under supply with voltage containing positive-sequence and negative sequence interharmonic injections of various frequencies. The phenomena that have been known from computer simulations only, are confirmed by experimental method. It is proved in this paper that positive-sequence voltage interharmonics have result in current subharmonics flowing in machine windings. The significant dependency between the frequency of voltage interharmonics and the amplitude of current subharmonics, which has been known so far from theoretical calculations, is confirmed experimentally as well.
PL
Sprawność silnika asynchronicznego klatkowego. Estymacja współczynnika sprawności silnika asynchronicznego klatkowego. Analiza istotności funkcji aproksymującej. Możliwości zastosowania w autobusach elektrycznych.
EN
The efficiency of asynchronous squirrel-cage motor. The estimation of squirrel-cage motor efficiency coefficient. The significance analysis of approximating function. The possibilities of application in electric buses.
EN
In the article a detection method will be analysed, which improves detection efficiency and assessment of dynamic eccentricity level. The method based on the analysis and selection of the characteristic features for stator current spectrum, which take the components related to the third harmonic current into consideration. Generally accepted assessment methods of variety faults are based on current spectrum analysis (mostly close to fundamental harmonic), with the assumption of sinusoidal voltage supplying and linear magnetic circuit. In case of simultaneous variety faults, the spectrum changes are often ambiguous. For example, the dynamic eccentricity and cage damage result in spectrum by appearing the harmonic with the same frequency. The assessment efficiency can be increased by broaden the harmonic components set, especially these, which are changing under the third harmonic component of stator current. Based on the measurements of low voltage motor, analysis results for different faults will be presented. The spectrum features caused by third harmonic stator current, which are unambiguously the evidence of a particular rotor fault, will be indicated.
EN
Selection of electric motors used in various kinds of industrial drives is realized at designing stage of that drives. But the exploitation condition of the machine not always can be properly foreseen at designing stage. And the exploitation condition (especially starting conditions) heavily influence electric motor’s working reliability. For middle and large capacity d.o.l. started induction motors the frequency and duration of their starts is of crucial importance for motor’s reliability. The motors for high frequency of starts and for long starting time (driving equipment of large inertia moment) should be specially designed. Proper design of the rotor cage for this motors is of high importance. Komel Center elaborated own methods and computer programs for designing rotor cages of large induction motors for heaviest starting conditions.
PL
W artykule przedstawiono liniowy model układu napędowego składającego się z przekładni zębatej oraz sterowanego wektorowo klatkowego silnika elektrycznego. Do budowy modelu dynamicznego przekładni zębatej wykorzystano metodę sztywnych (koła zębate, wirnik silnika) oraz odkształcalnych elementów skończonych (wały, obudowa przekładni). Ponadto zastosowano redukcję liczby stopni swobody modelu MES korpusu przekładni, co umożliwiło zamodelowanie napędu wraz z korpusem. Opracowany model układu umozliwia uwzgldnienie drgań giętno-skrętnych.
EN
A linear model of a driving system consisted of a gearbox and a vector controlled electrical motor in the paper is presented. Both, FEM and the rigid body method was used to obtain the dynamical model of the gearbox. In order to reduce the number of degrees of freedom of FEM model a reduction method was implemented. The final dynamical model of the system makes possible to analyze bending and torsional vibrations coupled.
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