Synchronous generator variable speed and constant excitation

[Vanguard]

TL;DR

will an electrically excited synchronous generator act as permanent magnet generator if provided with the similar excitation current at any speed?

The question is regarding an electrically excited synchronous generator.
Consider that this generator is not connected to the grid and thus not locked with the grid frequency.
This generator is spinning at variable speed and gets constant and similar excitation current
meaning that the excitation current does not change with the speed.
Will this in fact mean that this generator is acting as a permanent magnet generator?

 

[Baluncore]

Summary:: will an electrically excited synchronous generator act as permanent magnet generator if provided with the similar excitation current at any speed?

The question is regarding an electrically excited synchronous generator.
Consider that this generator is not connected to the grid and thus not locked with the grid frequency.
This generator is spinning at variable speed and gets constant and similar excitation current
meaning that the excitation current does not change with the speed.
Will this in fact mean that this generator is acting as a permanent magnet generator?

Welcome to PF.
The synchronous generator frequency is always proportional to the RPM.
The output voltage is proportional to the product of RPM and field strength.

If you replace the field with permanent magnets, then the voltage and the frequency will still be proportional to the RPM. So a fixed field current is the same as a permanent magnet field.

 

[Vanguard]

thank you.
I'm wondering if this kind of application makes sense over a PMSG.
would it be possible to use this kind of installation with a regenerative converter like in wind turbines
that usually use an induction machine or a PMSG.
Also, how would you determine what is the optimal excitation current?
intuitively, I would use the current that produces the rated voltage at rated speed (e.g 11kV@1500RPM)

 

[anorlunda]

Often, there is a feedback loop that compares terminal voltage with a set point, and manipulates excitation to hold that voltage constant.