Hi all,
i have not wrote on this site for a while but nw have the following problem that i have pondered over for a while!
I am currently a service engineer on varable speed 3.6 MW wind turbines and know that they use a asynchronous generator to convert the winds Kinetic energy into electrical energy, then convert the output varying AC supply from the asynchronous generator to DC then from DC back to the grid frequency of 50Hz AC using high power thyristors.
My question is with the start up of the asynchronous generator.
The below document i have been reading states;
"Grid Connection Required
On the page about the permanent magnet synchronous generator we showed that it could run as a generator without connection to the public grid.
An asynchronous generator is different, because it requires the stator to be magnetised from the grid before it works.
You can run an asynchronous generator in a stand alone system, however, if it is provided with capacitors which supply the necessary magnetisation current. It also requires that there be some remanence in the rotor iron, i.e. some leftover magnetism when you start the turbine. Otherwise you will need a battery and power electronics, or a small diesel generator to start the system). now im not sure what it means when it says you need to provide capacitors to supply the necassary magnatism?are these capacitors to create a phase shift to allow the stator to induce current in to the rotor?
also when the above states there will need to be a remanence left over in the stator to start the turbine......is this to charge the capacitors?
any help would be much appreciated.
PS the document i copied the above info is a really good one and can be found here.
http://www.talentfactory.dk/en/tour/wtrb/control2.htm
