Hello:
When calculating b4 for the Sepic, why is the resistance that C2 sees equal to R? It looks to me like R is in parallel to the series combination of the primary and secondary windings of the transformer. Why are the series windings not considered a short circuit therefore giving Req= 0?
Thanks
I'm wondering in general how the DC Transformer is to be treated..how's everyone else looking at it?
ReplyDeleteIn general, I believe that we need to see it as an ideal transformer, i.e. the impedance looking into the primary depends on the impedance seen on the secondary terminals and the turns ratio (and vice versa). Similarly, one should use the turns ratio and voltage or current on one side to relate to those values on the other side.
ReplyDeleteIn other words, the representation of a transformer implies mutual inductance between the primary and secondary, thus, those windings can't simply be viewed as a short circuit... unless the "other" side of the transformer is shorted out.
Specifically for the case of B4, the two windings in series will divide the Vtest voltage according to the turns ratio. If current was to flow through the windings, i1 and i2 would also have to be related by the turns ratio. Given that the ratio is not 1 and there is no other leg at the common node to "tap" current, i.e. Iprimary = Isecondary, the only value of current to satisfy that power on the primary is equivalent to power on the secondary is a current of zero. Also, primary and secondary currents are aligned with the dots, i.e. both "into" or "out of", implying that a straight series configuration could not have the possibility of any amount of current flow without disrupting the power balance of the transformer (even with a turns ratio of 1). With a finite voltage on each winding and zero current, the impedance would appear to be infinite.
I hope that explanation is wholly correct and makes sense.
Would others please review, verify, correct, or improve, as needed, as I would like to avoid misleading anyone if I have a misunderstanding myself?
DC transformer is an ideal transformer. The definition can be found textbook Fig.3.2 and Fig.3.3, pages 40-41, and in many other locations throughout the textbook.
ReplyDeleteFrom what I can tell based on the discussions on pages 40-41, (for finding the b's) we can pull R and C2 to the left through the ideal transformer..giving L1 || (D'/D)^2*C2 || (D'/D)^2*R || (C1 + L2)???...this seems to work for some but not all instances in solving for the b's...although there is an error in the solution, I'd doubt there are several errors which my method concludes. Thoughts? This may be a very simple something I'm just not seeing at the moment.
ReplyDelete