Showing papers by "Lauri Kutt published in 2008"
17 Oct 2008
TL;DR: In this article, the effects of active and reactive power consumption and losses depending on voltage level variations around the normal (rated) voltage level are focused on load response to the voltage change, while motor-type and mixed residential load is observed.
Abstract: This paper is focused on the effects of active and reactive power consumption and losses depending on voltage level variations around the normal (rated) voltage level. Supply voltage variations from rated voltage affect both power consumption and losses in the network. Focus is put on load response to the voltage change, while motor-type and mixed residential load is observed. Relations between voltage variation and load power consumption are suggested. Comparisons based on literature as well as classical theory and on-site measurements are presented.
10 citations
17 Oct 2008
TL;DR: In this article, a simple reactive power compensator solution for the spot-welding machines is described. But the focus is also put on the transformer saturation and current transients that can emerge from deployment of such reactive power compensation methods.
Abstract: High-power industrial spot-welding machines make use of transformers that have very high reactive power consumption. Simple reactive power compensation schemes cannot be used however, because of the cyclic nature of the spot welding transformer operating. This paper describes the development of a simple reactive power compensator solution for the spot-welding machines. Focus is also put on the transformer saturation and current transients that can emerge from deployment of such reactive power compensation methods.
6 citations
17 Nov 2008
TL;DR: It is found that the current waveform can be made sinusoidal if the instant power passing through the converter is proportional to the squared instant value of the mains voltage and/or the output voltage and current of the converter are in inverse proportion.
Abstract: The distortion of an AC-DC converter current could be corrected by use of a fast-controlled impedance-matching transformer on a basis of a non-conducting converter with alternating of parallel and series resonance. The basics of the converter performance and operation are described. Changes in the converter input impedance can be eliminated by means of the varying transformation ratio. It is found that the current waveform can be made sinusoidal if the instant power passing through the converter is proportional to the squared instant value of the mains voltage and/or the output voltage and current of the converter are in inverse proportion.
17 Oct 2008
TL;DR: In this article, an investigation conducted almost 10 years ago revealed that one of the causes for transformer breakdown was ferroresonance effects and a new specification for the voltage transformers was issued by Estonian Power Company.
Abstract: An investigation conducted almost 10 years ago revealed that one of the causes for transformer breakdown was ferroresonance effects. As a result a new specification for the voltage transformers was issued by Estonian Power Company. Now the first of transformers with improved characteristics have been in service for years, any further breakdowns have been experienced. This paper looks at the improvements to the specifications that leaded to the improvement of the voltage transformers reliability.
30 Sep 2008
TL;DR: In this article, a fast-controlled impedance-matching transformer on a basis of a non-conducting converter is proposed to correct the distortion of a waveform shape of AC/DC converter current.
Abstract: In principle, a distortion of a waveform shape of AC/DC converter current could be corrected by use of a fast-controlled impedance-matching transformer. Changes in the converter input impedance can be eliminated by means of the varying transformation ratio of this transformer. The paper considers a practical performance of the fast-controlled impedance-matching transformer on a basis of a non-conducting converter. It is found that the shape of current waveform can be made sinusoidal if the instant power passing through a converter is proportional to the squared instant value of the supply voltage and/or the output voltage and the output current of the converter are in inverse proportion. A non-conducting converter with alternating of parallel and series resonance meeting requirements is considered. The converter topology, an operating principle and output voltage control are described. The basics of the converter calculation and the converter current waveform modeled on computer are presented.