In this paper a comparison of numerically determined and measured electromagnetically exited noise of an induction motor is presented. The calculations are accomplished using FEM for an example motor, which is a 290 kW inverter-fed asynchronous machine. The approach starts with the electromagnetic and mechanical consideration. The focus is set on acoustic considerations, which contain the 3D-FE-model and measurement setup in the sound chamber.

Filtering nonwovens produced with melt-blown technology are one of the most basic materials used in the construction of respiratory protective equipment (RPE) against harmful aerosols, including bio- and nanoaerosols. The improvement of their filtering properties can be achieved by the development of quasi-permanent electric charge on the fibres. Usually corona discharge method is utilized for this purpose. In the presented study, it was assumed that the low-temperature plasma treatment could be applied as an alternative method for the manufacturing of conventional electret nonwovens for the RPE construction. Low temperature plasma treatment of polypropylene nonwovens was carried out with various process gases (argon, nitrogen, oxygen or air) in a wide range of process parameters (gas flow velocity, time of treatment and power supplied to the reactor electrodes). After the modification, nonwovens were evaluated in terms of filtration efficiency of paraffin oil mist. The stability of the modification results was tested after 12 months of storage and after conditioning at elevated temperature and relative humidity conditions. Moreover, scanning electron microscopy and ATR-IR spectroscopy were used to assess changes in surface topography and chemical composition of the fibres. The modification of melt-blown nonwovens with nitrogen, oxygen and air plasma did not result in a satisfactory improvement of the filtration efficiency. In case of argon plasma treatment, up to 82% increase of filtration efficiency of paraffin oil mist was observed in relation to untreated samples. This effect was stable after 12 months of storage in normal conditions and after thermal conditioning in (70 ± 3)°C for 24 h. The use of low-temperature plasma treatment was proven to be a promising improvement direction of filtering properties of nonwovens used for the protection of respiratory tract against harmful aerosols.

The considerations presented in the paper relate to one of the most intriguing phenomena, which is the development of oil whirls and oil whips in rotors with journal bearings. This effect is sometimes referred to as flutter, as its origin is in some relation to self-exciting vibrations of the system. Despite the fact that the flutter has been an object of investigation in numerous research centres all over the world, its nature has not been sufficiently recognized yet. The present paper delivers a description of particular phases of development of the hydrodynamic instability and proposes diagnostic determinants for this state. The object of investigations also included bearings with hybrid lubrication and siphon pockets in the oil gaps. The answer has been received to the question whether the self-exciting vibrations in rotating machines can be avoided, or reduced by means of additional oil supply having the form of siphon oil.

The paper presents the control concept for an experimental rig with closed-loop controlled pneumatic axis. The objective is the convenient execution of diverse control technologic experiments using free implementable control structures. Since two actuators can be mechanically linked to one another, one is force controlled to generate defined disturbances. Furthermore, a particular simulation model, which can be integrated in the controllers' user program, is pointed out including non-linear effects. Finally, selected experiments are discussed.