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• Design of laboratory measuring device. • Measurement pulling force burdens drifted by transport rollers. • Measurement of the active power of the electric motor. • Detection coefficients friction during the movement of the piece load against transport rollers. The paper presents an experimental measurement of a pulling force and determination of a friction coefficient during driven transport rollers' movement in a continuous transport system. To implement an experimental measurement, a laboratory machine was designed, enabling an experimental detection of a friction coefficient during movement in the contact surface of the transported load and the roller casings. The values of friction coefficient were determined for three material types: wood, plastic and rubber against the acrylic paint sprayed on a steel roller's casing. Experimental pulling force measurement with a tensometric load sensor was realized for three different angles of the roller conveyor's inclination. The results made it possible to determine a mean value of friction coefficient during movement between the contact surfaces of the three materials and the coating of driven rollers casings. The results can be implemented to digitize and monitor operation of electric motor machines. [ABSTRACT FROM AUTHOR]

• Measurement proposal to identify failure condition. • Measuring device design. • Measurement of pressing force magnitude in various rollers arrangement. • Experimental determination of force acting on pressure roller. Sandwich conveyors are among continuous transport systems used to transport bulk materials over short distances. The principle of their operation deploys the one of classic belt conveyors. However, in contrast to them, they use two parallel conveyor belts, between which the bulk material is transported. The conveyor belts are pressed against transported material by pressure rollers. As a result of mutual interaction, forces emerge which make transport of bulk material possible at angles that conventional belt conveyors cannot handle. The magnitude and effect of these forces are most pronounced at the points of conveyor belt's contact with pressure rollers. However, in case of insufficient pressure, the transport process fails, and the conveyor is unable to perform its function. Through experimental measurements, it was found that the pressing force magnitude is about 20.8% smaller compared to the opposite arrangement and a roller spacing of 330 mm, and by 13.4% with a roller spacing of 660 mm. The aim of the paper is to design a measurement system and identify the magnitude of forces, using experimental measurements, based on which regression models can be determined and used in failure analysis. The paper presents results that can be applied in online monitoring of this type of transport for the needs of failure analysis, prediction, and operational indicator's assessment. Thus, preconditions are created to include such a type of transport system among the ones meeting Industry 4.0 criteria in the field of failure analysis. [ABSTRACT FROM AUTHOR]

Contact connections in electrical machines and apparatus are important elements in the whole power supply network and a high level of reliability is expected there. Contact resistance is a fundamental criterion in the design of an electrical contact or contact system. The contact resistance should be as low as possible to minimize losses due to the current passage and the related heating of the contact connection. The value of the contact resistance depends on the material used, the value of the applied force, the type of contact, and, last but not least, the quality of the surface and chemical layers. In this paper, an initial diagnosis of the contact material is performed based on the determination of the sample's specific resistivity by the four-wire method and the evaluation of the measurement uncertainty. The work is followed by the design of a testing device that uses crossed bars to measure the change in contact resistance as a function of the magnitude of the applied force. An analysis of the sample mounting method is performed here using FEM simulations of the current field and shows the interaction between the holder and the sample in terms of current line transfer. The proposed system is then used for experimental measurements of the material-dependent coefficient KC for verification of existing or newly developed materials in electrical engineering, where the values of the KC coefficient are not known. Finally, the paper also deals with the measurement of fritting voltage for individual contact pairs having surface quality corresponding to brushing. [ABSTRACT FROM AUTHOR]