Zugl.: Jena, Univ., Habil.-Schr., 2007

<p>This thesis describes a method of measuring axial magnetic leakage flux in an operational hydropower generator. Axial magnetic leakage flux is the magnetic flux at the ends of a rotating generator, which goes through the stator parallel to the rotor axis. This flux can cause circulating currents in the stator iron, giving rise to losses, and can in the worst case overheat a generator, causing it to melt down. To measure the axial flux, and how it affects the generator temperature, a measurement system was constructed on behalf of Vattenfall. The system consists of search coil sensors and a signal-processing unit with amplifiers and active filtering.  To confirm the behaviour of the axial leakage flux and the functionality of the measurement system, a test installation was made. The result from the measurement shows how the leakage flux increases when the generator runs in underexcited operation.</p>

This thesis describes a method of measuring axial magnetic leakage flux in an operational hydropower generator. Axial magnetic leakage flux is the magnetic flux at the ends of a rotating generator, which goes through the stator parallel to the rotor axis. This flux can cause circulating currents in the stator iron, giving rise to losses, and can in the worst case overheat a generator, causing it to melt down. To measure the axial flux, and how it affects the generator temperature, a measurement system was constructed on behalf of Vattenfall. The system consists of search coil sensors and a signal-processing unit with amplifiers and active filtering.  To confirm the behaviour of the axial leakage flux and the functionality of the measurement system, a test installation was made. The result from the measurement shows how the leakage flux increases when the generator runs in underexcited operation.

This report tested the possibility of using induction as a mean for transferring data and power so that it can be implemented as a communication medium between a terminal and measuring head mounted in a measuring frame. This would eliminate the need for the cable bunches that are used today. For testing, signal generators were used to generate FSK-signals and were transferred with the help of inductors to the oscilloscope for signal detection, this to see how the coils used in the tests behaved. Simulations of a PLL were performed to see how good it could handle FSK-demodulation. With the help of a PLL IC and the simulations a working FSK-demodulator could be assembled. This showed that the simulations and reality is in good agreement. The final results shows that it’s possible to transfer FSK-modulated data in either direction but that the desired effect isn’t possible to transfer because of the existing coupling factor that exist in the coils core used in the test. / I denna rapport testas möjligheterna att använda elektromagnetisk induktion för att överföra data och elektrisk effekt för kommunikation media mellan terminal och mäthuvudet i en mätram som används vid framställning av papper. Detta skulle kunna eliminera behovet av de besvärliga kabelbuntar som används idag. I testerna används signalgeneratorer för att generera en FSK-modulerad signal som representerar den data som överförs via spolar. Efter detektering studeras signalen på ett oscilloskop för att se hur de spolar som användes i testerna beter sig. Även simuleringar av en PLL utfördes för att se hur bra den kunde hantera FSK-demodulering. Med hjälp av kunskaper från simuleringar och en PLL IC-krets kunde en fungerande FSK-demodulator byggas ihop. Det visade att simuleringarna och verkligheten stämmer bra överens. De slutgiltiga resultaten visar att det är möjligt att skicka FSK-modulerad data i båda riktningar utan komplikationer. Den önskade effektöverföringen visar sig dock inte vara möjlig på grund av den mycket låga kopplingsfaktorn mellan spolarna som användes i testet.

Hohenheim, Univ., Diss., 2005.

Universiẗat, Diss., 1999--Kaiserslautern.

Universiẗat, Diss., 1999--Hannover.

Universiẗat, Diss., 1998--Kaiserslautern.

Stuttgart, Univ., Diss., 2007.

Techn. Universiẗat, Diss., 2005--Berlin.