The paper formulates some objections to the methods of evaluation of uncertainty in noise measurement which are presented in two standards: ISO 9612 (2009) and DIN 45641 (1990). In particular, it focuses on approximation of an equivalent sound level by a function which depends on the arithmetic average of sound levels. Depending on the nature of a random sample the exact value of the equivalent sound level may be significantly different from an approximate one, which might lead to erroneous estimation of the uncertainty of noise indicators. The article presents an analysis of this problem and the adequacy of the solution depending on the type of a random sample.
In the paper, the mathematical model of coupled electromagnetic and thermal phenomena in the pulse transformer taking into account the magnetic hysteresis is presented. For the mapping of magnetic hysteresis, Jiles-Atherton model is applied. In order to solve field equations, the finite element method (FEM), "step-by-step" procedure and Newton-Raphson algorithm are used. Software elaborated on this basis is used for analysis of hysteresis loss in the core. Selected results of investigations are shown.
The paper presents an FE model of coupled electromagnetic and thermal phenomena in Line Start Permanent Magnet Synchronous Motors (LSPMSMs). An algorithm for solving equations of a discrete model using the FEM has been presented. On the basis of this algorithm the author’s personally developed software for the analysis of coupled electromagnetic-thermal phenomena in the LSPMS motors was elaborated. This software was used to analyze the start-up process of motors with identical stator and rotor magnetic circuits and different materials of the starting cage. The start-up process of motors with the squirrel-cage made of aluminum and copper was considered. The influence of temperature on the start-up process has been taken into account. The results of simulation tests were compared with the results of measurements.