Replacing a reverse acting AVR with forward acting AVR 1

[BK32]

Hi all,

We currently have a requirement to investigate replacing our existing Jeumont Schneider reverse acting AVRs.

The existing alternator is an indirectly self excited machine. The stator part of the generator excitation system comprises a differential compound winding arrangement (a shunt field and a differential series field winding). The shunt field is the main field winding and is fed from a normal compound excitation circuit. The differential winding is excited by the AVR.

If I wanted to just feed the shunt winding with the compounding circuit plus a forward acting AVR. What else would need to be looked at?

Alternatively, instead of it being a differential compound wound machine, could I get a forward acting AVR and wire up the series field winding for a cumulative effect? What are the specific things I need to look at to achieve this?

 

[waross]

Do you have the instruction manual?
Link
I have seen saturable reactor or transformer regulators with series boost with and without an AVR.
Basically, the constant voltage transformer or saturable transformer supplies the field and the no load voltage of the generator is determined by the output voltage or current of the saturable transformer.
If the generator voltage is less than the desired generator voltage, the machine may be operated with no AVR or with a forward acting AVR.
If the generator voltage is more than the desired generator voltage, the machine may be operated with a reverse acting AVR.
There may be a rheostat in the circuit to reduce and adjust the voltage applied to the brushless exciter, and as a result, the generator output voltage.
A series boost may be added, and if the machine is to be operated without an AVR, a series boost must be added. The output of a current transformer monitoring the load current of the generator is dropped across a resistor and the resulting voltage is added to the output of the saturable transformer to set the generator output voltage and to compensate for the internal impedance of the generator.
Adjusting the value of the resistance across the CT output will determine the amount of compensation and influence whether the system will run with a forward acting AVR, no AVR or a reverse acting AVR.
To change from a reverse acting AVR to a forward acting AVR, the output of both the saturable transformer and the series boost CT must be trimmed to a little less than 100%.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[BK32]

Thanks waross,

Is there any benefit in connecting the AVR to the series winding over connecting it to the shunt (compound) winding? Will the response of the excitation system benefit in any way?

I imagine that connecting the AVR up to the shunt winding as the series boost will require the AVR to provide the current compensation wholly. Whereas, if it was decided to leave the existing current compensation circuit as it is, and leave the AVR acting on the differential or cumulative series winding that it would then just be used to perform fine control wrt current compensation.

Hence, if the AVR only has to perform fine control is it more likely to respond more quickly than if it is performing the full series boost? Is this beneficial?