Flyback "transformer" is NOT COUPLED INDUCTORS

I am very happy to read such a good post ??. . Thank you Prof Cuk.?

So Alexander, what you are saying is because the devices look identical physically when NOT connected in a circuit, then they must obviously be the same animal and behave the same, when placed into any arbitrary circuit! This is not true, as the device's behavior is changed by the circuit configuration it is placed in, and the various elements making up the device are separated out (distilled as it where), and reconfigured according to the dictates of the circuit. To wit: the device takes on a new citizenship commensurate with its new home - you cannot ignore circuit configuration and its influence on the magnetic device's behavior. Lenz's law clarified the beauty of Faraday's transformer by noting that any o/p current is always met with an equal and opposite primary current, such that their magnetomotiveforces or MMF (Ampere-Turns IN) on the core cancel each other out, and this is why an o/p load 1000 times larger than what is needed to completely saturate and collapse the magnetic core, is allowed to pass through the transformer, having ZERO impact on core flux (limited only by size of copper wire). Now for this to work both windings must be operational at the same time, so that there is a real time primary reflected load current that will balance the o/p load current, and thereby leave the core totally unaffected. This clarification that Lenz put forward describes the primary functionality of the transformer, where a tiny magnetization current is out of phase with both the in-phase pri and sec winding voltages. Yet pri and sec load currents which are 180 degrees out of phase with each other with pri current out of phase with pri voltage, also manages to be out of phase with magnetization current itself at the same time. So an ac transformer requires that coils are coupled in real time (Lenz's law - 2 coils operational at the same time), and it is not enough to be simply wound on the same magnetic core. It is not just coupling to the core that matters, but also a real time coupling between the coils themselves as well. What does all this really mean in practice? It means if one coil is open circuit while the other is not, then YOU DO NOT HAVE AN AC TRANSFORMER OPERATING AT ALL. It also means the ac transformer is not an energy storage device, as it's core energy is minuscule compared to the o/p load energy that is 1000x greater. In other words, the fake fly-back transformer (i.e. chimera-Xformer) consists of two inductors, and the two coils are NOT OPERATIONAL AT THE SAME TIME (due to circuit operation), and ipso facto there is no transformer here, as Lenz's law is not operational in the sense of a binding of the 2 coils together. So what is happening here? First i/p coil is used to charge magnetic device's energy storage byway of its air-gap (absent in Faraday's gap less Xformer), while at the same time o/p coil is NOT OPERATIONAL. Only one coil is operational in the ON-time sub cycle period. Then in the OFF-period i/p coil is no longer operational (switch is off), and energy is now transfered from the core's air-gap energy storage to the o/p coil's circuit (i.e. square wave voltages on the coils have reversed). There is no simultaneous cooperation between the two coils. If the two coils are not simultaneously operational during either the ON or OFF periods, then the coils not being coupled in real time, it is not and does does not constitute an ac TRANSFORMER. This is why a different symbol should be used to convey this difference in behavior. So how does a flyback magnetic device where coils are never simultaneously operating at the same moment in time, manage to be classified as a transformer, which by definition requires continuous operation between the coils? Let alone the difference that one stores magnetic energy to process a 2-step energy transfer, while the other stores no significant energy at all! You need to explain this before a claim is made that a fly-back device is a transformer, and what is given above proves this claim cannot be made. Topology people! That is what decides how a magnetic device will behave in any given circuit, and there are 3 elements of behavior of a magnetic device that are juggled together depending on circuit operation. It is possible for a magnetic device to be configured as an inductor, and then later reconfigured in a different mode to be a real transformer, but that is not the case with the fake fly-back chimera-transformer. And if truth be told it is not even a good inductor device. Dr. Cuk with nearly half a century of experience behind him should know what he is talking about. It is surprising to see professionals in this field who do not understand the basics of this field, and who would be better advised to learn from that knowledge base rather than debating for debating's sake. Trust me the inventors knows better. It really is time this subject matter should be put to rest. To appreciate the new topologies this subject matter should be mastered first. OK, end of rant! This response took a life of its own.

Manoj, your Professor Ramnarayanan Venkataramanan (his full name) has indeed taught you very well! He was one of more than dozen of my PhD students who ended up becoming Professors of Power Electronics worldwide. We called him in our Power Electronics Group Ram for short. I understand that he had a very successful career at IIT Bombay now Mumbai in India and retired a few years back. Please give him my highest compliments for teaching you kids properly and setting you well for a successful career in this exciting field. Out of 36 PhD students I supervised over 24 years of research and teaching at Caltech, others ended up in research institutions and in industry worldwide and in either design or management position. Dr. Slobodan ?uk (former professor at Caltech)

Agreed Mr. Cuk, my Prof. V Ramanarayanan @ IISc taught us its not a transformer and not a coupled inductor, this is what we have been taught.