I am looking for information on negative field current capability in static excitation systems. I am also looking of r information on how one can model this effect in any programming language.



Thanks

 

The maximum value of reactive power that a synchronous machine can take from network is determined by the direct axis reactance. Q= - V*V/Xd.

If synchronous machine has to handle more reactive power caused by capacitance of un-loaded transmission lines, negative field current is required to be supplied to the field winding of machine. However, since synchronizing torque starts to decrease after certain value of negative field current, negative excitation can not be increased after certain value i.e. Q= -V*V/Xq

Negative field current is possible in static excitation systems. A anti-parallel thyristor converter can be connected with main thyristor bridge to have four quadrant operation. Few utilities have installed this anti-parallel converter to meet additional requirement of reactive power absorption.

Rgds,

Pankaj Mishra

 

I have attempted to locate more information with regards to this negative field current. I have not been successful in locating adequate information to allow me to understand what this is, and how it is used and for what reasons.

I am looking for:

1) a drawing showing the excitation bridge with and without the components that illustrates with and without the negative field current components.

2) As well, I wish to see the vector drawings showing the Vt. Ef, (I x Xd), with and without the negative field current components. Would the author be able to provide some information on this or where I may go to find this information?

Thanks Len Y.

<b>Moderator's Note:</b> Since this is a post from 2004, can anyone help this poster? It not likely that Mr. Mishra will see this question.