Modeling excitation systems for brushless synchronous machines

[JPetersen]

Hi,

Wonder if one of you guys have been facing similar "problems":

I am modeling automatic voltage regulators and excitation systems for smaller synchronous machines. Size is typical 3-10MW, and the machines are 10-15 years old.

One of my main problems is how to derive the parameters for the exciter, ie. those describing the amplification and saturation effects. The path is the one going from the output of the AVR though the brushless exciter and rotating rectifier to the main field excitation terminals of the synchronous machine. I intend to use the IEEE frame AC5 for the brushless/rotating excitation system. I have no problem in modeling the AVR.

The only thing available for me is typically a routine test report. The IEEE model parameters Ke and Se are not directly available in the routine test. The routine test report however often include the no load/short circuit-characteristics, but these are unfortunately showing the exciter machine current VS the main machine terminal voltage. This means that the saturation effects for both exctiter machine and main machine is combined in one diagram. The IEEE AC5 model requires me to separate the saturation effect of both exciter machine and main machine.

I don't know if a type test report would be of any help.

Because the machines are 10-15 years old, I am not succesful in involving the manufactures....

Someone facing or even solved same issues??

Kind Regards
Petersen

 

[motorspert]

Petersen, its difficult to guess this data without help from the manufacturer - but as someone who used to fill these in, I can tell you all the saturation is in the machine, the exciter is normally designed to achieve a boost of say 1.6x volts so is almost linear at operating conditions. Assume the exciter is linear and work out saturation for the main machine and use that. the exciter timeconstant will be around 0.25s. Use these and see how sensitive the model is.