International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This paper describes the design and practical implementation of AC/DC/DC converter in mode of arc welding. An analysis of the operation of AC/DC/DC converter and its input/output characteristics are determined with computer simulations. The practical part is con- sisted of AC/DC/DC converter prototype for arc welding with output power of 3 kW and switching frequency of 64 kHz. The operation of AC/DC/DC converter is validated with experimental measurements.

This paper presents performances of two different types of PV cells under various temperature clime of Stip, R. Macedonia.
Stip with geographical position 41 .742N, 22.1 94E has 2260 sun hours yearly with average temperature 25 °C during spring.
The types of cells examined in this study are: crystalline silicone (c-Si) and polycrystalline silicon (p-Si). The calculations are made for various operating conditions and a comparation of I-V and P-V characteristics are represented here. Also, the efficiency and fill factor for photovoltaic (PV) cells is calculated based on simulation results.

We are witnessing the rapid growth of the energy prices and there are expectations that they will continue to grow in the future. Consequently, there is a constant need of energy efficiency improvements that could be achieved by decreasing of energy losses, smart and efficient energy utilization and conservation of energy resources.

The water supply systems are large energy consumers. So, the investments in the increasing of their energy efficiency will not only have an economic dimension, but also they could have large positive effect on the environment protection. In this paper, an analysis of the degree of efficient usage of the energy and the appropriate techno-economic analysis of the energy consumption for a real water supply system is presented. Few methods for increasing the energy efficiency of water supply pump stations and an analysis of the potential benefits of this method are proposed and discussed too.