The saturation characteristic of transformers is needed for EMT-type studies. However, usually, only RMS V-I pairs are available. Because under saturation condition the current is not sinusoidal, and the transformer core operation point is in the non-linear region, the conversion of this characteristic to instantaneous flux linkage - current pairs must be done with special considerations and methods. How is this conversion done?
Irms=0.707Imax Same for flux for linear region of B-H curve, would, not applicable in saturation. And the flux wave gets flat top, generating third harmonics in secondary voltage wave.
well that itself is the problem. I have rms values of voltage and magnetizing current; not the instantaneous pairs. It is also well known that for the parts in which the transformer enters saturation, the current waveform is non-sinusoidal. Hence we cannot just multiply the rms value by (2^0.5).
V-l modeling could help refer my paper," Laboratory methods to generate inrush current patterns for power transformers"....
To convert the V-I curve to Flux-current caracteristic, you can see my paper :''
Modified method for transformer magnetizing characteristic computation and point‐on‐wave control switching for inrush current mitigation''
This can be easily performed by the use of "L nonlinear data function" tool in EMTP-RV software environment.
excuse me, How can I convert the B-H curve of a transformer to Flux- Current?
Masood Moosavi to convert B-H curve to phi-i, you require knwoledge about the topology of the transformer core and its windings, equating the ampere-turns (N.i= ∫H.dl).
Behzad Behdani Thank you
Unfortunately, I am simulating an old transformer that I have no information about the size of its core
Do you think there is a way I can roughly convert the B _H curve to a flux-current curve?
Thanks in advance for your reply
Masood Moosavi You're welcome. If you have access to the transformer you can perform tests on it. You can apply voltage to the transformer and measure its no-load current up to the saturation region and achieve its core characteristic this way. However, you should make sure that you have enough reactive power available. Alternatively, you can turn into finite-element analyses with tools such as Maxwell, Comsol, ..., and simulate a core with the same topology and material as your desired transformer and acquire its characteristic through simulation.
Behzad Behdani
thanks a lot
Unfortunately, this is an old power transformer that is running in a sub-station, and I can not do the tests you mentioned.
may I have your email?
Thank you very much again
Masood Moosavi You may also use methodologies such as “Estimation of transformer saturation characteristics from inrush current waveforms” by S. G. Abdulsalam et al. if you have the transformer's recorded inrush current available.
You can send message here in the researchgate to me, I'll respond.
Behzad Behdani, the method you suggested is amazing. Thank you very much.
I think I can provide some data of the inrush current and estimate the characteristic of the transformer saturation core with this method.
another question. You mentioned above that the "L nonlinear data function" can convert the voltage-current characteristic to a flux-current. I try it sometimes but I can't get an output. How to get output from the "L nonlinear data function"?