Influence of the stator core shape on the parameters of small induction motor

Higher requirements concerning economical aspect of the production of induction motors encourage designers to look for new variants of motor construction. The small induction motors with stator core shape with cut of parts making stator yoke width not constant is an example of an atypical motor construction. The subject of this paper is a field-circuit and circuit analysis of this type of motor construction. The aim of this analysis is to determine the influence of the saturation of the magnetic circuit on motor parameters. It is shown that the cuts of the stator core have significant influence at standstill and less significant at load characteristics of induction motors. Comparisons with measurements are given. From comparisons between the results of the analysis and experiments, it is clarified that the use of presented circuit and field-circuit methods can estimate characteristics of induction motors with enough accuracy even for motors with specific construction like not round stator core

Performance characteristics of high-speed low-power induction motors

W pracy przedstawiono charakterystyki eksploatacyjne silników indukcyjnych małej mocy, o rdzeniach wykonanych z różnych gatunków blachy elektrotechnicznej, pracujących przy zasilaniu z sieci i z przemiennika częstotliwości napięciem o częstotliwości 100 oraz 200 Hz. Obliczenia zostały wykonane z wykorzystaniem metod obwodowo-polowych oraz metodami obwodowymi, z uwzględnieniem zjawisk nieliniowych oraz strat dodatkowych w rdzeniu i uzwojeniach silnika. W obliczeniach wykorzystano wyznaczone doświadczalnie dla badanych silników charakterystyki strat mechanicznych, a także pomierzone charakterystyki magnesowania stosowanych blach elektrotechnicznych oraz charakterystyki stratności blach w funkcji indukcji magnetycznej wyznaczone dla zakresu częstotliwości do 2000 Hz.The paper presents operational characteristics of a small induction motor with the stator core made of amorphous laminations, supplied from mains or frequency inverter at 100 and 200 Hz. Calculations were performed using field-circuit and equivalent circuit approaches taking account of non-linearity and additional losses both in the core and in the windings. Data for mechanical losses, magnetisation curve and magnetic losses of the amorphous material was obtained experimentally; magnetic measurements were taken as a function of magnetic flux density in the frequency range up to 2,000 Hz

No-load curves of the high-speed small size induction motors

Nowadays the high-speed induction motors are widely used in many industrial installations and also in aircraft industry. Many of them are designed as converter-fed induction machines. Some electrical drives with not so sophisticated speed control have voltage shape with many higher harmonics. Examine the operation of high speed induction motors feed from PWM converters, with wide range of frequency, it is necessity for carefully considering of no-load losses of the motor. Results of formulas used in computer aided design for calculation of mechanical losses and core losses have shown good agreement with experimental data for motor feed from sinusoidal 50 Hz source but they have been not valid for higher frequencies. The main aim of the paper will be analysis of the no-load losses and no-load current for some small power induction motors feed with voltage of frequency from 50 to 250 Hz with different U-f ratio. For this problem circuit and field-circuit methods will be use and the results will be validating and computation methods will be improving basing on experimental results

Basic and additional core losses of the high-speed small size induction motors

The paper presents the calculation of the basic and additional core loss of the small size induction motor supplied from the power network for 50 Hz, and by a voltage-frequency converter for the frequency changing from 0 to 250 Hz. The calculations were made by use the field - circuit method, as well as by use known from the literature circuit methods. The calculation results were verified by measurement. Calculations were performed using the measured characteristics of the specific core losses of the electrical sheets as a function of the flux density and frequency

Influence of core material on the work of the high-speed small size induction motors

In designing the high-speed low-power induction motors should be pursued to obtain operating characteristics similar to characteristics of general purpose motors and the greatest efficiency at rated load. One way to increase the efficiency of induction motors, particularly those working at higher frequencies, is applied to the motor core electrical sheets with improved magnetic properties and less core losses, including amorphous iron. The paper presents a comparison of measured operating characteristics of several low-power induction motors, a core made from three types of electrical steel, working with supply from the inverter voltage with a frequency varying in a wide range (from 0 to 200 Hz), and grid-supplied frequency 50 Hz and 100 Hz. In the case of grid-supplied motors paper presents the results of calculations made using the available methods from the literature, with particular emphasis on determining the additional losses in both the no-load and at rated load. The calculations used, experimentally determined for the tested motors, the mechanical loss characteristics, and also measured the magnetization characteristics for electrical sheets and sheet specific losses as a function of magnetic flux density for a wide range of frequencies

Modelling of static and dynamic characteristics of small induction motor

W pracy przedstawiono wyniki modelowania obwodowego i obwodowo-polowego charakterystyk elektromagnetycznych małego (370 W) silnika indukcyjnego przy biegu jałowym i w stanie zwarcia. Pomierzone charakterystyki pozwoliły na weryfikację obliczonych parametrów schematu zastępczego silnika. Parametry te zostały wykorzystane w obliczeniach obwodowych przebiegów rozruchowych silnika zasilanego napięciem sieciowym. Porównanie wyników wskazuje na dobrą adekwatność stosowanego modelu obwodowego.In last years the speed-control drives with inverter-fed induction motors more and more are used. In inverter-fed motors additional phenomena due to high voltage/current harmonics may occur. Thus, the necessity to modify mathematical models of induction motor's should be taken seriously into consideration to make possible electromagnetic calculations in static and dynamic states as well. In the paper are presented the results of the electromagnetic characteristics' modelling of a small induction motor (370 W) using circuit method and circuit-field one as well, in no-load and short-circuit states of the machine. The modified motor's model should take into consideration the higher motor's harmonics as well as non linear phenomena such as magnetic circuit saturation, displacement of currents in rotor bars [3] and parametric resonance [5], if any, i.e. their influence on equivalent circuit parameters of the motor. Therefore, the calculation of motor's field distribution was necessary using field and circuit calculation methods. Next, these parameters have been used in order to calculate - using the circuit method - the start characteristics of the motor when supplying with network voltage. Applying the measured motor characteristics the verification of the calculated motor's equivalent circuit parameters has been done, in no-load and short-circuit states of the motor. The calculations and measurements of currents have been done when supplying motor with network sinusoidal voltage as well as with PWM inverter. Relevant results are shown in sequence in Fig. 2 (r.m.s. currents' values) and Fig. 3 (relative differences between calculated and measured currents related to measured value when supplying with sinusoidal voltage). In Figs 10, 11, 12 the measured and calculated courses of phase currents, electromagnetic torque and speed during free acceleration of the motor are presented. The comparison of measured and calculated results proves a good adequacy of the circuit model used