Winding Techniques for Switch mode Transformers - Page 1
Forum section: electronics / beginners

author: khatus
author_rank: Regular Contributor
timestamp: August 22, 2019, 11:05:00 pm
content: Hello guys i want to know the Winding Techniques for Switch mode Transformers.I have watched few video in you tube but can not understand how to implement the phase opposition in real hardware(i.e in transformers).

author: Jwillis
author_rank: Super Contributor
timestamp: August 23, 2019, 01:18:11 am
content: The winding techniques or methods are the same for any transformer.The only difference is with increasing frequency the fewer the windings and the smaller the core can be.This all has to be calculated based on the parameters you require . Size , voltage, current and the material of the core.This determines at what frequency you can operate the transformer.The direction of your secondary in relation to the primary makes no difference provide that all secondary windings are in the same direction to each other.

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 23, 2019, 10:18:19 am
content: Quote from: khatus on August 22, 2019, 11:05:00 pmThe dot is traditionally interpreted as the start of the winding, simple as that. See, for example, this explanation:https://www.electricaltechnology.org/2013/12/transformer-phasing-the-dot-notation-and-dot-convention.htmlThat said, the image you linked to shows a flyback converter, in which the transformer operates a bit differently. In all transformers, when the dot end of the primary is positive so will the dot end on all of the secondaries (and when the dot end is negative, etc...). Apply that rule to the flyback and you'll see that when the primary switch turns on current flows into the non-dot end of that winding which means the dot end will be negative, and the secondary dot end will also go negative but the series diode prevents current from flowing at that time. When the primary switch turns off the polarity of all windings will flip and now the dot ends are positive so current can flow out of the secondary. This means energy was stored in the core by the primary when the switch turned on, and transferred out of the core by the secondary and diode when the switch turned off. In a conventional transformer the goal is to store as little energy as possible in the core, but in a flyback transformer the goal is the opposite, but this radical difference in goals typically only requires adding an air gap to the core of the flyback transformer.Hopefully that explanation isn't too deep in the weeds...

author: khatus
author_rank: Regular Contributor
timestamp: August 23, 2019, 12:25:54 pm
content: I want to know about how to implement in real hardware.How to wind a transformer that its primary and secondary are in phase opposition?I have watched a video about it but since the owner of the video is an Indonesian i can not understand his words?https://youtu.be/-OUaMWKzDcc?t=34How to implement interleaved winding in flyback transformer(i.e on bare frame we place half of the primary winding and then secondary winding entirely and over it the second half of the primary)

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 23, 2019, 07:42:13 pm
content: Quote from: khatus on August 23, 2019, 12:25:54 pmAnd I already answered you in sufficient detail - along with the links and pics that are also in this thread - for you to get on with winding a transformer yourself.Wind all windings in the same direction and treat the start as the dot end. For a flyback transformer, connect the start of the primary to the positive power rail and the end to the switch, and connect the end of the secondary to the anode of the output diode and the start to output ground (assuming a positive output voltage). If you want to interleave the primary and secondary then first wind half of the primary, then the entire secondary, then the other half of the primary, and join the end of the first primary to the start of the second.

author: soldar
author_rank: Super Contributor
timestamp: August 24, 2019, 10:38:48 pm
content: Quote from: khatus on August 23, 2019, 12:25:54 pmYou cannotwinda transformer so that primary and secondary are in opposition. You canconnecta transformer so windings are in phase or in opposition. I mean, a turn is a turn. If you turn the other way and you connect it the other way then nothing has changed.

author: Jwillis
author_rank: Super Contributor
timestamp: August 25, 2019, 03:32:17 am
content: Quote from: khatus on August 22, 2019, 11:05:00 pmIn the video he was winding a custom transformer for his SMPS.The secondary he used bundles of wire on the winding to pass more current instead of a single larger gauge wire. Phase opposition is a bad thing and I don't understand why anyone would purposely do it. The only way to get phase Opposition is with either two primary winding's opposing each other or to secondaries winding's opposing each other .But all that does is cancel out the opposing phases and your left with the difference. You simply can't oppose the primary with the secondary because it simply inverts the AC cycle. Nothing more. If your looking to lag current then simple using a choke in series will do that .If you want to lead current then use a capacitor in series.I don,t understand your goals or am I missing something.

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 25, 2019, 10:58:19 am
content: Quote from: Jwillis on August 25, 2019, 03:32:17 amThe primary and secondary don't conduct at the same time in a flyback transformer. Energy is stored in the core by the primary when the switch turns on, and is released from the core through the secondary (and diode) when the switch turns off.

author: soldar
author_rank: Super Contributor
timestamp: August 25, 2019, 11:40:41 am
content: Like in many threads people come in and spout whatever is on their mind or they answer questions that were not asked and the thread becomes a mess of people posting things that are true but irrelevant, things that are mistaken and also irrelevant. Can we please read the question again?Quote from: khatus on August 22, 2019, 11:05:00 pmThe answer is that you do not "implement the phase opposition in real hardware" because it makes no sense. You wind the transformer and it is how you connect the windings later which determines whether they are in phase or in opposition.Really. It is very simple.This is like asking how to make nails such that the point end is pointed towards the wood and the head is towards the hammer. The answer is that you don't do that. You make the nails and when you use them you make sure they are pointed in the right direction and flip them around if necessary.