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Experimental study of current damages in bearings.

Edvall M., Fyhrman M., Lindsten G., Blennow J., Thiringer T.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

2007

Vol. 46, nr 19

141-146

Failures of bearings in electric motors related to electrical damages started to increase after the introduction of the fast switching pulse width modulated IGBT inverter on the market in the mid 1990s. The aim of this work was to investigate how the damages occur. Shaft voltage, mechanical load, speed, lubricant and discharge energy were some of the parameters considered. The threshold voltage level was found to be mostly dependent on the oil film thickness which in return depends on speed and load. Shaft voltage proved to be the dominant factor in creating damages on the bearing surface. The film is capable of holding a higher voltage before breakdown under high frequency voltages as compared to slowly increasing voltages. Speed and load did not seem to affect the discharge energy but affect the pattern of the damages. Damages were also observed on the bearing lubricated with low impedance grease to the same extent as with conventional grease.

Grid integration of wind turbines

Thiringer T., Petersson A.

Przegląd Elektrotechniczny

2004

R. 80, nr 5

470-475

In this overview paper, the three most common wind turbine systems are described and their interaction with the grid is discussed. The three main systems are: the traditional stall-regulated fixed-speed system, the full-power converter variable-speed system and finally the doubly-fed induction generator (DFIG) variable-speed system. The power quality and the response to grid disturbances are presented. Variable-speed turbines have a better impact compared to fixed-speed turbines. The response to grid disturbances is also generally better for variable-speed turbines, however, large voltage dips cause a very large short-term impact from the DFIG system.

W tym przeglądowym artykule opisano trzy najpopularniejsze systemy turbin wiatrowych oraz ich oddziaływanie na sieć. Omówiono system prędkości generatora indukcyjnego, system sprzęgnięty z siecią poprzez przekształtnik energoelektroniczny oraz system z generatorem indukcyjnym pierścieniowym dwustronnie zasilanym. Zagadnienia jakości energii oraz reakcja na zakłócenia występujące w sieci zostały również zilustrowane.