Tag Archives: load

1155–1164 V. Osadčuks, A. Pecka and A. Galiņš
Usage of grid support inverter on long distribution grid lines
Abstract |

Usage of grid support inverter on long distribution grid lines

V. Osadčuks*, A. Pecka and A. Galiņš

Latvia University of Life Sciences and Technologies, Faculty of Engineering, Institute of Energetics, Čakstes blvd. 5, LV-3001 Jelgava, Latvia
*Correspondence: vtl@tvnet.lv

Abstract:

The paper focuses on the evaluation of new possibilities to improve voltage quality in remote branches of 230 V grid. Decrease of power electronic costs may potentially make battery-backed inverters a viable alternative to the costly reconstruction of 230 V distribution grid connections, which are of poor quality or cannot match changing load requirements, extending power transmission lines or adding boost transformers. The object of the current study is a household-type consumer with 20 A single-phase connection to distribution line with a distance of 2 km to a 20 kV transformer station. The calculated resistance of the power line is 2.8 ohms. The load profile was captured during 5 days in summer and 10 days in winter and was used to calculate the capacity of the grid support equipment. Measurements indicated, that in the worst case 2% of time the voltage was below 10% of nominal and 8% of time – below 5% of it. This is outside of the regulatory limits of EU and national regulations. The experimental setup for a voltage quality improvement system was based on an OutBack Power Radian series grid inverter with 7 kW output power. Battery consisting of 12 V 120 Ah VRLA accumulators wired in 48 V system was used. The inverter was configured to work in grid support mode using battery power when the consumer’s active load increased above 1.2 kW. Results showed improvement in voltage quality over the full consumer load range. The total efficiency of the grid support system was 89%. The use of DC bus and batteries allows easy incorporation of renewable energy sources, thus giving the opportunity to scale power and battery capacity of the system. An Additional benefit of using a battery-backed inverter in grid support mode is that consumer can temporarily use more power that is allowed by grid due to its capacity constraints.

Key words:

, , ,




1708-1719 H. Kalkis, Z. Roja and S. Babris
Faults and the physical workload in sawing and packing-related woodworking processes when considering potential ergonomic solutions
Abstract |
Full text PDF (526 KB)

Faults and the physical workload in sawing and packing-related woodworking processes when considering potential ergonomic solutions

H. Kalkis¹²*, Z. Roja³ and S. Babris⁴

¹Riga Stradiņš University, Faculty of European Studies, Dzirciema street 16, LV-1007 Riga, Latvia
²University of Latvia, Faculty of Business Management and Economics, Aspazijas blvd 5, LV-1050 Riga, Latvia
³University of Latvia, Ergonomic Research Centre, Jelgavas street 1, LV-1004 Riga, Latvia
⁴BA School of Business and Finance, K. Valdemara 161, LV-1013 Riga, Latvia
*Correspondence: henrijs.kalkis@gmail.com

Abstract:

The forest sector is a high-risk economic sector in Latvia, one in which manual work, awkward postures, the tightening up of individual muscle groups, and work monotony still exists. The aim of this study was to analyse the physical workload and fault modes, and their effects on the sawing and packing processes in woodworking when considering potential ergonomic solutions. Results show that packing operators and saw operators alike are exposed to severe loads, and these results coincide with survey results in which employees in these professions complain about the physical load and mention lower back pain. Fault modes and their effects on the sawing and packing processes were analysed using Failure Mode and Effects Analysis, and the main errors which were revealed in packing operations were related to machinery and lifting equipment, as well as to ergonomics and errors involving the human factor. The risk priority was calculated in terms of a figure. Financial indices were compared before and after any potential improvement in the sawing and packing processes. Analysis proves that investments in the improvement of ergonomics in relation to the automation of the production process saves human resources and is economically favourable when it comes to ensuring the sustainable development of the business in question.

Key words:

, , , ,




349-356 V. Bulgakov, V. Bandura, M. Arak and J. Olt
Intensification of rapeseed drying process through the use of infrared emitters
Abstract |
Full text PDF (635 KB)

Intensification of rapeseed drying process through the use of infrared emitters

V. Bulgakov¹, V. Bandura², M. Arak³ and J. Olt³*

¹National University of Life and Environmental Sciences of Ukraine, 15, Heroyiv Oborony street, UA03041 Kyiv, Ukraine
²Vinnytsia National Agrarian University of Ukraine, Soniachna street 3, UA21008 Vinnytsia, Ukraine
³Estonian University of Life Sciences, Kreutzwaldi 56, EE51014 Tartu, Estonia; *Correspondence: jyri.olt@emu.ee

Abstract:

The theoretical basis of the agricultural material drying techniques has been formed in the world for two and a half centuries. Nevertheless, despite the multitude of studies well presented in the literature, the industry still lacks universally recognized methods of design calculation for the majority of drying problems. Presumably, this is due to the fact that the dehydration of foodstuffs is one of the most energy-intensive and complicated work processes. In the process of thermal treatment during the drying, the physical state of the water in the treated item changes, the properties of the item itself are altered.
Recently, the drying of foodstuffs by means of infrared (IR) radiation has been gaining ever wider acceptance. At the same time, the technologies for dehydrating foodstuffs and materials are now far ahead of the theory of drying. Not only the classical literature on the drying problems, but even special studies on the subject cannot provide any specific recommendations for the design of installations with the electro-magnetic principle of energy input. Whereas that is exactly the type of installations that are now actively making headway, while offering serious challenges in their modelling. For that reason, experimenting has until now been the only reliable way of their studying. Despite the available extensive scientific literature on the drying, including works on IR units, the practical issues of engineering IR driers have not been tackled. All the existing studies consider solely particular cases. This study discusses the process of drying the fixed bed of rapeseeds with the use of the electromagnetic infrared emitter. The energy intensity of the process and the optimum thickness of the product bed are determined. The aim of the paper is to examine the effect that the operating condition parameters (energy input intensity, temperature, grain bed thickness) have on the drying kinetics and the energy characteristics of the process. The methods of research are based on the thermophysical analysis of the material’s structure. The experimental studies were carried out with the use of monitoring and measuring equipment, up-to-date methods and instruments, including solutions developed by the authors. The analytical treatment was performed with the use of the software packages: MathCAD, Excel. The sample testing and examination took place in the laboratory and the methods were in compliance with the applicable standards. A comprehensive experimental investigation of the effect that the operating parameters (specific load and power) have on the rape seed IR-drying kinetics had been accomplished.

Key words:

, , , ,