Behaviours of a transformer questions.

[nwman]

Hello all,

I asked this question in a different thread and category but I think it would be more suited for this category. I'm working with a few ideas of other people and I'm a novice when it comes to electrical physics and magnetism. How ever I do know a little and have seen a few good ideas that I am working on improving. So on to my questions:

First of all I have a question about how the core size of a transformer effects the transformer. For example if you had a transformer that looked like the one below. Where the core inside the primary coil A is smaller (say 1/2) then the core inside the secondary coil B. Lets also say A and B coils have the same number of turns. How would this effect the power transfer through the transformer?


Also, at what saturation level does a transformer work at? Is it below, at, or above the core's saturation point.

Thanks

Tim

[valveman]

Core size is irrelevent.  The size of the core is determined by what size of wire your using in the transformer and number of windings.  i.e. use the smallest core size that will do the job.

However shape of the core can be important.  It depends on how you want the magnetic field to interract.  Look up toroid transformers.

Saturation of the core is dependant on a few factors.  Material used for the core and frequency of operation.  For instance, most transformers used in powersupplies use  metal that is layered in slices to help reduce the effects of eddy currents.  High frequency cores are made of many matereials.  These are usually powered down, mixed and formed using an epoxy in the form desired.

Saturation of a transformer is not a good thing.  This means that the transformer cannot keep-up with the rate of changing magnetic field.  This will cause the transformer to overheat and eventually fail.

Robert

[nwman]

Thanks for the input and more is always welcomed. I think this answers most of my questions. I'm in the process of having a modified transformer made and I'm just trying to think through what I might see when its finished and how to test it. More questions probably will fallow.

Tim

[gyulasun]

Hi Tim,

If you have not seen this link it is worth reading,  an interesting pondering on some of your questions.

http://amasci.com/elect/mcoils.html       Its Fig.11 and downwards is especially interesting. For the iron core that can be curved / bended,  insulated iron wires (garden wires) that are led close parallel to each other i.e. bunched could be used   

A useful (text book) info on magnetic core characteristics that includes saturation is here:

http://focus.ti.com/lit/ml/slup124/slup124.pdf

Also the first page here shows nicely the saturation on a core's B-H curve:

http://www.powerit.vt.edu/AA/chapters/pdffiles/c4pdf.pdf


rgds,  Gyula

[nwman]

Thanks Gyula,

Those are great resources. A little over my head in some cases but that's what I need.

Tim