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Induction motors are a significant consumer of electricity. Therefore, their energy efficiency level plays a vital role in the world's energy balance. The world's markets strive to produce motors of efficiency class IE3 or IE4 while maximizing the use of wire and magnetic materials. However, high induction values in the motor core can also lead to significant losses in construction materials, especially in the magnetic motor housing. This article aimed to show how it is possible to determine the distribution of the magnetic field and additional losses in the yoke and the cast-iron motor frame using field-circuit methods to model the motor and to refine the analytical method for calculating these losses at the motor design stage. [ABSTRACT FROM AUTHOR]

The technologies of cutting the cores of electric machines change the magnetic properties and the loss of the electrical sheets used, affecting the machine’s parameters, mainly power losses and efficiency. This is particularly important in the case of induction motors, which are a significant consumer of electricity. Therefore, the problem of increasing their efficiency is important from the point of view of environmental impact. The article presents a method of approximating a material’s magnetic properties based on the results of measurements carried out with specimens of various widths. The presented method allows for an approximate representation of the changes in the structure of the material caused by the cutting technology. It is used in the analytical method for calculating motor parameters, and gives results that are in good agreement with the measurement. This method can determine the operating parameters of electrical machines of various sizes and rated powers.

The method of cutting motor core sheets causes a change in their magnetic properties and core losses, especially additional losses. Reducing motor losses is very important because of the fulfillment of increasingly stringent requirements set by international regulations for reducing electricity consumption. Due to fact that more and more often induction motors are supplied with high-frequency voltage, core losses are beginning to play a dominant role in the motor’s loss balance. That is why accurate determination of these losses is very important and cutting has a significant impact on them. This report shows how the method of cutting sheet metal affects losses in the finished induction motor working in a wide frequency range. The paper presents the impact of various motor core fabrication technologies on its operational parameters and an approximate way of including this impact in analytical calculations at the design stage of new machine designs, as it is necessary to use sheet metal cutting technologies such as laser or electrical discharge machining (EDM) at the prototype stage. The proposed method is based on measurements of sheet parameters made on toroidal samples with appropriately selected dimensions, so that the width of the sample corresponds to the average width of the motor core elements.

Induction motors are an important consumer of electricity. Among induction motors, speed-regulated induction motors have the greatest energy-saving potential. However, motors operating in a very wide speed range require a completely different approach than motors operating on a single supply frequency. An example of such motors are the drives of industrial washing machines. The article aimed to present how using field-circuit methods, but above all, analytical methods increase the efficiency of such a motor by changing its design. Thanks to the change of the design and the core material, it was possible to obtain the efficiency of the motor for the frequency of 10 and 20 Hz, meeting the requirements of the IE1 efficiency class specified for the frequency of 50 Hz, while for the frequency of 10 Hz it is 17.9% higher than in the currently produced motor, and for 20 Hz—by 11.1%, while for the frequency of 350 Hz the level of efficiency was corresponding to class IE4. The presented considerations may be the basis for such a procedure for other drives with similar properties. Additionally, an important element of the article is the refinement of the analytical method of determining core losses. [ABSTRACT FROM AUTHOR]

This paper presents various methods of increasing the efficiency of an asynchronous motor operating over a wide frequency range. Small power motor of rated power of 1.1 kW which is typically used in industrial washing machines and in centrifuges of blood samples was considered. The paper shows that using the presented methods it is possible to upgrade the efficiency of the motor to IE3 class or even IE4 class not only for 50 Hz, but for a wider frequency range. [ABSTRACT FROM AUTHOR]

In this study, the authors aimed to analyse the influence of massive ferromagnetic shaft on the distribution of the electromagnetic field and to evaluate the magnetising current from the mains. To achieve this, they used motors powered by 50 and 200 Hz. They also used both numerical two-dimensional (2D) and 3D field-circuit methods as well as an analytical method based on the results of field analysis. This modified analytical method is based on the magnetisation characteristics of the shaft's material. According to the results, there was a significant impact of shaft's saturation on the machine with one pair of poles in the form of a significant increase in the amplitude of induction in the rotor yoke, which resulted in an increase in the magnetising component of the current drawn by the motor from the grid. This phenomenon was found to increase, in particular, when using non-magnetic shafts. In the case of machines with two pairs of poles, this effect was found to be much smaller than that of one pair of poles. They verified the results experimentally by comparing the calculated and measured magnetising currents. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the interbar current taking into account of the contact resistance between the secondary conductor and the steel sheets of squirrel-cage induction motors using the 3-D parallel finite element method. As a result, the effects of the contact resistance on the interbar current are clarified. [ABSTRACT FROM AUTHOR]

The hysteresis motor produces the torque by magnetic hysteresis. The short-duration overexcitation of the hysteresis motor running at synchronous speed reduces the stator current and increases the pull-out torque at the same time. This excellent effect after one-time overexcitation lasts theoretically forever. However, the sudden changes of stator voltage or load torque reduce and vanish it. The duration time of the effect after one-time overexcitation has not been clear in the continuous operation without stator voltage or load torque changes. We used the three-phase balanced voltage source and measured the duration time after one-time overexcitation under no changes of the stator voltage and load torque. It was found that the effect by one-time overexcitation lasted for two weeks of the experimental period. It seems that the effect will last forever. It is clear that electric power saving operation of the hysteresis motor using short-duration overexcitation is quite useful. [ABSTRACT FROM AUTHOR]

The subject of this work concerns the problem of signal diagnostics of induction machines carried out in the time-and-frequency domain. It was assumed that the signal carrying the important information about the current state of the machine is the measured signal of the axial flux. The basis for the diagnostic decision making was the analysis of the energy of the detailed wavelet representation, obtained as a result of the use of a specially constructed orthonormal transformation basis. To ensure sufficient resolution of fault detection, the authors constructed orthonormal wavelet basis based on the recursive formulas for generating higher order Legendre polynomials. The construction of the orthonormal basis was carried out using the scaling function, which was designed using the appropriately scaled Legendre polynomial. The synthesis of the basic wavelet and the orthonormal basis was based on the recurrent dependencies of the multi-resolution analysis using the relationship between the elements of the quadrature mirror filters. Dependencies between elements from two consecutive levels of decomposition were used. By applying the constructed orthonormal basis, the research on the nature of the energy flow of an axial flux signal of an induction motor between adjacent frequency bandwidths in steady-state depending on the machine load was presented. Studies have shown that significant flows of the diagnostic signal energy occur between the adjacent frequency bandwidths periodically at frequency of about 2.5 Hz. This periodic energy flows of the axial flux signal hamper fault detection and diagnostic decision making. The analysis results confirmed that it is possible to ensure a sufficient level of selectivity of a diagnostic system by means of this method. To ensure a sufficient efficiency of diagnostic systems it is required to separate flow effects from fault symptoms. [ABSTRACT FROM AUTHOR]

Nowadays requirements for electrical motors are getting bigger due to the new energy standards. This paper presents some new version of expert system supporting automatic design of induction motors. The inference engine was used and the.NET technology was applied. Also the correction module has some new features. Due implementation of well configured knowledge bases, it is possible to create cheaper motors with better parameters. [ABSTRACT FROM AUTHOR]

This paper presents the core losses and performance characteristics of a small power induction motor with the core made from different electrical sheets, supplied from mains or PWM frequency inverter at 50, 100, and 200 Hz. Field-circuit and analytical methods are used for loss calculations, taking into account the nonlinear phenomena and additional core losses. In the calculations, the characteristics of mechanical losses measured against the speed for the motors and different electrical sheets magnetization, for frequencies up to 2000 Hz, as well as losses density characteristics against the flux density were used. The results show a significant increase in core losses concomitant with the motor load increase. In addition, analytical methods were used to calculate the performance characteristics versus load power. Calculated results were verified by measurements. [ABSTRACT FROM PUBLISHER]

This paper presents a comparison of losses at no load and full load of six different induction motors which rated powers are between 3 kW to 280 kW. The results show that additional core losses are strongly dependent on the load of the motor. The reason is the saturation of rotor tips which leads to an increase of the effective slot openings and the strengthening of harmonic by the induced currents in rotor cage. That leads to significant increase in additional core losses concomitant with motor load increases. For loss calculations, field-circuit and analytical methods are used. Using the FEM is presented an in-depth analysis of the phenomena at no-load and load indicating the reasons for increasing losses at the load conditions. Additionally, improved analytical method was employed to calculate the curves of stray losses versus load power. The results for no-load losses, stray losses and efficiency are compared with the measurements and good agreement was obtained for both field-circuit and analytical method. The change of stray losses versus output power was compared with formula proposed by IEC 60034-2-1 standard. The assigned values of stray load loss were found to be generally lower than average test result for motor with rated power below 18.5 kW and generally higher for motors with bigger rated power. In situations where a fixed value of stray load losses may be required the obtained curves can be used. [ABSTRACT FROM AUTHOR]

The paper describes calculations method of heat transfer coefficient for finned induction motor housing and equivalent thermal conductivity for air zones inside this housing. The method is based on Computational Fluid Dynamics (CFD). In addition, the results of thermal calculations to verify calculated values of coefficient are presented. [ABSTRACT FROM AUTHOR]

This paper presents operational characteristics of a small induction motor with the stator core made of amorphous laminations, supplied from mains or a frequency inverter at 50, 100, and 200 Hz. Calculations were performed using field-circuit and equivalent circuit approaches, taking account of nonlinearity and additional losses, both in the core and in the windings. Data for mechanical losses, magnetization curves, and magnetic losses of the amorphous material were experimentally obtained; magnetic measurements were taken as a function of magnetic flux density in the frequency range up to 2000 Hz. Calculated results are compared with measurements. [ABSTRACT FROM AUTHOR]

This paper presents a no-load core loss analysis of a three-phase energy-saving small-size induction motor supplied by a sinusoidal voltage. In the field-circuit approach, the distribution and changes of magnetic flux density in the motor are computed using a time-stepping finite-element method. The discrete Fourier transform is used to analyze the magnetic flux density waveforms in each element of the motor model. The rotational aspect of the field is included by introducing a correction to the losses generated by the first harmonic of magnetic flux density. The core losses in each element are evaluated using a loss curve measured on a toroidal core at different frequencies. Finally, an approximate analytical formulation is derived for rapid field computation. The results are compared with measurements. [ABSTRACT FROM PUBLISHER]

Speed-controlled induction motors have the most significant potential for energy savings. The greatest problems with obtaining high efficiency occur in motors with a wide range of rotational speed regulation, as in the motors for driving industrial washing machines under consideration. While for the highest speeds, the dominant phenomenon is at field weakening. The problem is obtaining the optimal size of the magnetic flux for low rotation speed to prevent excessive saturation increasing current, and reduction of efficiency. This problem is usually solved by selecting the appropriate control for an already built machine. The authors propose a combination of activities when designing the motor structure with the selection of proper control, which allows for high efficiency. Since the drive does not require precise speed control or obtaining the required dynamics, it was possible to use an inexpensive control in an open loop, avoiding the cost of transmitters. Furthermore, the number of design parameters that are subject to change is significantly limited by technological factors and the available space in the washing machine. Proper parameter selection was made using a peripheral method assisted by field-circuit simulations. The proposed approach can be used in designing structures and selecting motors controls for other applications. [ABSTRACT FROM AUTHOR]

In the drives of high-speed devices, such as a blood centrifuge, dynamic states also play an important role in terms of the time and quality of the tests performed. The article presents the application of modified equations resulting from the mathematical model of an induction motor to model dynamic phenomena during motor start-up, both with mains supply and with frequency start-up. The applied solution considers the phenomenon of current displacement in the rotor bar and the phenomenon of saturation. The comparison of the obtained results with the experiment shows that the method is sufficiently accurate. The obtained results can also be extended to higher power machines and to modeling other dynamic states. [ABSTRACT FROM AUTHOR]

The technologies of cutting the cores of electric machines change the magnetic properties and the loss of the electrical sheets used, affecting the machine's parameters, mainly power losses and efficiency. This is particularly important in the case of induction motors, which are a significant consumer of electricity. Therefore, the problem of increasing their efficiency is important from the point of view of environmental impact. The article presents a method of approximating a material's magnetic properties based on the results of measurements carried out with specimens of various widths. The presented method allows for an approximate representation of the changes in the structure of the material caused by the cutting technology. It is used in the analytical method for calculating motor parameters, and gives results that are in good agreement with the measurement. This method can determine the operating parameters of electrical machines of various sizes and rated powers. [ABSTRACT FROM AUTHOR]

The method of cutting motor core sheets causes a change in their magnetic properties and core losses, especially additional losses. Reducing motor losses is very important because of the fulfillment of increasingly stringent requirements set by international regulations for reducing electricity consumption. Due to fact that more and more often induction motors are supplied with high-frequency voltage, core losses are beginning to play a dominant role in the motor's loss balance. That is why accurate determination of these losses is very important and cutting has a significant impact on them. This report shows how the method of cutting sheet metal affects losses in the finished induction motor working in a wide frequency range. The paper presents the impact of various motor core fabrication technologies on its operational parameters and an approximate way of including this impact in analytical calculations at the design stage of new machine designs, as it is necessary to use sheet metal cutting technologies such as laser or electrical discharge machining (EDM) at the prototype stage. The proposed method is based on measurements of sheet parameters made on toroidal samples with appropriately selected dimensions, so that the width of the sample corresponds to the average width of the motor core elements. [ABSTRACT FROM AUTHOR]

The hysteresis motor produces the torque by magnetic hysteresis. The short-duration overexcitation of the hysteresis motor running at synchronous speed reduces the stator current and increases the pull-out torque at the same time. This excellent effect after one-time overexcitation lasts theoretically forever. However, the sudden changes of stator voltage or load torque reduce and vanish it. The duration time of the effect after one-time overexcitation has not been clear in the continuous operation without stator voltage or load torque changes. We used the three-phase balanced voltage source and measured the duration time after one-time overexcitation under no changes of the stator voltage and load torque. It was found that the effect by one-time overexcitation lasted for two weeks of the experimental period. It seems that the effect will last forever. It is clear that electric power saving operation of the hysteresis motor using short-duration overexcitation is quite useful. [ABSTRACT FROM AUTHOR]