I am running some simulations on synchronous machine. It is based on
q-d transformation that it breaks down to q and d transformer model.
Saturation is also implemented into the model. I expected to see
distortion on my stator current due to saturation. (It happens to
transformer) However, it is not happening on the stator current. It did
not get distorted. I talked to my professor. He gave me an answer that
is becasue of the magnatic path now is rotating and that's the reason
the current is distorted. However, I do not understand why. I wonder if
there is anyone out here can answer me this question.
First of all, the synchronous machine d-q model is not a transformer
model -it is, in fact a DC model of conditions as seen from the stator. You
do have direct and quadrature axis mmfs and direct and quadrature axis
fluxes are affected by saturation (and damping windings or their
equivalents). This is, for steady state, a DC situation, unlike that of a
transformer. The effect of saturation, as seen from the AC or stator side is
one of a change in the internal voltage generated by the field current with
respect to the unsaturated situation. In other words, stator mmf as seen
from the rotor boosts or bucks the (DC) direct and/or quadrature mmf and the
amount of boost or buck depends on saturation. This will not cause a
distortion in the stator current as it appears as if it is a change in
field current (or a change in reactances)
If there are DC components in the stator currents, these will be seen as
fundamental frequency components of the mmf as seen in the rotor but then
damper winding currents (including eddy currents) will come into play as in
a transformer. These will be reflected back as second harmonics in the
stator and these can, in theory, be distorted by saturation but will one
notice this distortion?
Does your model deal with this?
Note that the usual saturation model for a synchronous machine is as
expressed by Krause "Analysis of Electrical Machines" McGraw Hill, 1986,
The one thing that you can hold a a dogma is that: "the more you know about
synchronous machines, the more you are aware of your ignorance"
Don Kelly email@example.com
remove the X to answer
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.