generator exitation problem

I do not understand 'coils' and how they relate to the AVR. The AVR should have a current rating. If the new AVR can produce as much field current as the old AVR it will produce the same stability and voltage to sustain a load of the same kW rating as before. So check old AVR amp rating and new one.

Seems like you had an AVR that was capable of sensing both load and voltage(i.e. input), or one that had additional functions apart from voltage sensing at the inputs. You need to give more details on what AVR you had AND the new replacement to get any meaningful assistance. Most manufacturers give possible connection drawings to help you properly instal and configure. Please note that, if your new AVR lacks the load sensing functionability, it may be for a lower rating generator. More details, thanks.

Are yo saying that your generator has two separate field inputs (excitation fields), or do you mean one coil is the PMG (permanent magnet generator) and the other coil is the field?

Usually 'self-excited' means the generator has a PMG that creates the necessary voltage the field needs (via the AVR) for the generator to generate power. By using only one coil are you saying that the AVR no longer uses the PMG as it's power source?

If those 2 coils were both exciter coils then useof only one will reduce the strength of the exciter field and reduce thereby the output of the generator.

j.

In generators with decreasing the number of exciting parallel current path for constant At/coil providing in air gap, we must increase the excitation wire cross section, or increase the number of generator pole, or increase the number of slots per rotor pole.

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send the drawing of exciter/generator.