Modeling and Measurements of the response of asynchronous machines exposed to voltage dips

Examensarbete för masterexamen

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Type: Examensarbete för masterexamen
Master Thesis
Title: Modeling and Measurements of the response of asynchronous machines exposed to voltage dips
Authors: Andersson, Johan
Abstract: Asynchronous machines (induction machines) are widely used in the industry. A high trustiness is required since an interruption of the operation due to a voltage dip can result in both economical losses and safety problems. An example is the security system in a nuclear power plant that includes a high number of asynchronous machines which are driving important pumps and fans. It is therefore of high interest to know how these machines respond to irregular voltages. This master thesis deals with the dynamical response of asynchronous machines exposed to voltage dips. This is done by simulations in Simulink using the fifth order Park model. To verify the results, simulations of a 4 kW machine has been compared with measurements on a laboratory set-up. Both simulations and measurements are based on disturbance profiles compiled by OKG, the owner of Oskarshamn nuclear power plant. The results from the simulations agree well with the measurements. It is shown that the speed of the machine is decreased when it is exposed to a decreased voltage. When the voltage recovers the machine draws a higher current from the source due to the magnetization and the acceleration. The magnitude of the current depends on the duration of the dip and on the magnitude of the remaining voltage. Lightly loaded machines are less affected by voltage dips, under- and over-voltages. This is something that is taken into account by OKG when dimensioning. The aim is to load the machine to a level where the stator current is at rated level when the voltage level is at 85 percent of rated. It means that the machines simulated in this project withstand most of the Disturbance Profiles.
Keywords: Elkraftteknik;Electric power engineering
Issue Date: 2010
Publisher: Chalmers tekniska högskola / Institutionen för energi och miljö
Chalmers University of Technology / Department of Energy and Environment
Collection:Examensarbeten för masterexamen // Master Theses

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