This paper intends to develop a more accurate approach for determining the no-load iron losses in pulse width modulation (PWM) inverter fed induction motors. The proposed method is validated by means of a prototype motor with a plastic rotor cage. The iron losses have been computed by the time-stepping finite element method, both with sinusoidal and PWM supply. The iron losses have then been estimated by adding up the contribution generated by orthogonal components of the flux density, as if the iron losses generated by these components were independent phenomena. The rotational hysteresis losses, as well as excess ones, have been calculated applying a correction factor based on experimental data. These factors are a function of the peak flux density and ellipticity of the B vector loci. Experimental validations are provided for several frequency and magnetic saturation values. In addition, this paper demonstrates the necessity to consider the harmonics initial phase in order to increase the accuracy in the iron loss prediction.

In this paper, two different methods for iron loss prediction are analyzed. The first method is based on the classical separation of loss contributions (hysteresis, eddy-current, and excess losses). The model requires loss contribution separation using iron loss measurements with sinusoidal supply. In this paper, this method will be called the ldquolow-frequency method.rdquo The second method, named the ldquohigh-frequency method,rdquo is based on the assumption that, under pulsewidth modulation supply, the higher order flux density harmonics do not influence the magnetic work conditions. These magnetic conditions depend only on the amplitude of the fundamental harmonic of the flux density. In this paper, both the proposed methodologies and the related measurements are described in detail, and the obtained results are compared with the experimental ones. The experimental results show that both methods allow getting excellent results. The high-frequency method is better than the lower one but requires a more complex test bench. Depending on the accuracy required by the user, the more handy method can be chosen, with the guarantee that the estimation errors will be lower than 5%.

This paper presents a method to estimate the magnetic properties and width of a damaged area which is the result of the carried out punching process. Both a finite-element method (FEM) numerical model and a method for estimating the damaged area width are proposed based on data obtained from the noninvasive measurements as well as on an experimental study of the crystallographic structure. In addition, the authors propose an algorithm, using the FEM numerical model, to identify the equivalent magnetic properties of the material in the damaged area. The results obtained from the FEM model were compared with those obtained by the analytical formula proposed earlier.

This paper presents a new concept of the single sheet tester (SST) with variable dimensions. First, the author points out standards specifying requirements for systems, that allow to determine the properties of soft magnetic materials. Then, the concept of the SST system and its calibration are described in detail. Calibration of the system was carried out both by performing additional measurements as well as by Finite Element Method (FEM) modeling and execution of numerical simulation. Using the described measuring system, the measurements of two grain-oriented magnetic materials cut at an angle of 0° and 90° with respect to the rolling directions, were executed. The results of the measurements were compared with results obtained from the Epstein frame (carried out in accordance with the International Electrotechnical Commission international standard). Moreover, the author refers to other SST systems having nonstandard dimensions.

The authors deal with the problem of estimating the zone width of damaged magnetic materials, which is the result of industrial processes adopted for the lamination sheet production. The authors propose two approaches: the former uses the 3D FEM model, while the latter proposes an analytical formula. Both approaches use the results of measurements performed on toroidal samples. The final result of the study is the comparison between the width of the damaged zone computed with the two proposed approaches and the comparison between the calculated and measured power losses.

The paper describes the quantification of negative impacts of assembly processes on the stator core properties of fractional kilowatt motors. The considered motor powers are in the range of 100-500 W. In this context, the authors deal with the effects of the assembly technology (i.e. the clamping, and welding), punching process, and pressing of the stator core into the motor housing. The deterioration of the magnetic properties of the stator core is reflected in the motor performance, such as the current consumption and the efficiency. The authors conducted both experimental activities and 2D/3D FEM simulations, necessary to determine the three factors of merits. These proposed factors aim at quantifying the negative impacts of the considered assembly processes. The obtained results are critically discussed and compared with those reported in other researches.