Scientific Journal of Gdynia Maritime University

The current issue of the Scientific Journal of Gdynia Maritime University features papers spanning diverse topics from the fields of technology and engineering. The papers present research results relevant to automation engineering, electronic and electrical engineering, mechanical engineering, as well as production management.

The paper “Effect of Voltage Fluctuations on Induction Motor Currents” focuses on voltage interference, one of the power quality disturbances found in electrical power systems. Cyclic voltage fluctuations are related to each other by the presence of subharmonics and interharmonics, which are components with frequencies lower than the fundamental frequency or not an integral multiple of the fundamental frequency. Preliminary research is presented related to a four-pole squirrel-cage induction motor with a rated power of 4 kW under voltage fluctuations with a frequency greater than that of the supply voltage. It was found that for the tested motor using symmetrical rectangular modulation with a frequency in the range of 60 to 90 Hz, the current interharmonics corresponding to the subsequent harmonics of the modulating function were significantly smaller than the current subharmonics and interharmonics corresponding to the first harmonic of the modulating function. For the modulation of interest in this work, the frequency of the torque pulse components, corresponding to the individual current subharmonics and interharmonics, was higher than the natural frequency of the rigid-body torsional vibration. Consequently, there was virtually no risk of rigid-body torsional vibration.

Power system lines are used not only for the transmission of electrical power, but also to carry a communication signal, known as ‘mains communication voltage’. Considering electrical power quality, mains voltage should be considered as interharmonics – frequency components that are not multiples of the total fundamental frequency. These components have a detrimental effect on various energy consumers, including rotating machinery. The paper “Effect of Mains Communication Voltage on Induction Motor” is an investigation into the effect of interharmonic frequency components of an electric current on electromagnetic torque pulsation for a four-pole squirrel cage induction motor with a rated power of 3 kW. The results show that, for the interharmonic frequency range corresponding to the mains communication voltage, the moment of inertia of the driven unit has a relatively small or even negligible effect on the current interharmonics and torque pulsations of the motor. The authors suppose that it is probably due to the strong damping of speed fluctuations by the motor's moment of inertia for the interharmonic frequency range considered.

The paper “Application of the Vivaldi Antenna in a Linear Antenna Array for Radar Systems” presents a novel design for a broadband TSA antenna with an expanding aperture to be the primary radiating element in a multi-component antenna design. The proposed TSA antenna has a bandwidth of 0.87 [GHz] (2.35 to 3.22 GHz) at SWR < 2 and 0.55 [GHz] (2.50 to 3.05 GHz) at SWR < 1.3. Based on the tests carried out, the author’s concluded that the input resistance is stable over the entire operating range and close to 50 Ω. The design of the TSA antenna supplied via a half-wave loop was proven to be a far superior solution to the model of the same antenna supplied via a half-wave dipole, as evidenced by the results acquired from the SWR and radiation pattern measurements.

3D printing, also known as additive printing or additive manufacturing, has become part of today’s manufacturing technologies, enabling the rapid fabrication of three-dimensional items from a variety of materials, and thus facilitating rapid prototyping and personalisation of products. In “Effect of Temperature and Printing Angle in FDM Additive Printing on the Strength Properties of PET-G”, the authors undertook to evaluate the effects of selected 3D printing parameters on the strength properties of glycol-modified polyethylene terephthalate. The highest tensile strength was achieved by the specimens printed at an angle of 90^o and 230^oC. The temperature and printing angle were found to have no significant effect on strain.

The paper “Analyzing the Implementation Process for the Kaizen Method on the Example of ZSP „LUBIANA” S.A.” describes how Kaizen was implemented between 2018 and 2022 at ZSP „LUBIANA” S.A. The outcome of the process completed at ZSP „LUBIANA” demonstrated major significant benefits from improvement of the production process and better commitment of the company’s personnel. The procedures discussed in the paper included aspects related to monitoring and evaluating the effectiveness of the solutions applied, which is an important part of maintenance and continuous development of the site’s Lean Management System.

Robert Starosta