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Quick Transformer Question

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JohnS_AZ:
Toroidal power transformers ... How (electrically) do they differ from regular old iron laminate core transformers?

I'm looking at this one ...

http://www.allelectronics.com/make-a-store/item/TTX-128/12VCT-8A-TOROIDAL-TRANSFORMER/1.html

TechGuy:

--- Quote from: JohnS_AZ on October 01, 2010, 05:23:12 pm ---Toroidal power transformers ... How (electrically) do they differ from regular old iron laminate core transformers?

I'm looking at this one ...

http://www.allelectronics.com/make-a-store/item/TTX-128/12VCT-8A-TOROIDAL-TRANSFORMER/1.html

--- End quote ---

Rule #1: There is no such thing as a "Quick Transformer question"

Electrically there is no significant difference. EMI is different as toroidal cores usually emit more EMI than E-Core transformers. They leak a lot of magnetation energy from the donut hole. Toriod cores may have better efficiency and better magnetic coupling between the primary and secondary(s), depending on how they are wound. Toriod have superior thermal dissapation than E-Cores. as the provide more exposed surface area for the windings.

60/50 hz transformers use laminated plates whether they are toriod or e-core. Some high efficiency 60/50hz transformers will use tape wound foil instead of plates to reduce eddy current losses

A e-core transformer is a a pair of toriod cores, that are joined in the center. The difference is that all of the winding is in a limit area instead of all around like in a toroid.

Personally I prefer ecore transformers over toriods they are easier to mount and much easier to wind (when I make my own custom transformers). I do use toroid power inductors in non-isolated DC-DC converters, as they are better than rod core inductors, and have good thermal disspation. The only time I would buy a toriod 60hz transformer, is if I couldn't find a compatiable e-core transformer that meet the output voltage and power requirements.

Zero999:

--- Quote from: TechGuy on October 01, 2010, 06:10:32 pm ---Electrically there is no significant difference. EMI is different as toroidal cores usually emit more EMI than E-Core transformers. They leak a lot of magnetation energy from the donut hole. Toriod cores may have better efficiency and better magnetic coupling between the primary and secondary(s), depending on how they are wound. Toriod have superior thermal dissapation than E-Cores. as the provide more exposed surface area for the windings.
--- End quote ---
Are you sure they're more leaky?

Surely if the coupling then there should be less leakage?

I prefer toroidal transformers because of the reasons you describe. I agree they're harder to wind though so the only sane option is to but one ready made. As far as mounting is concerned:I find it easier than E core transformers. Some have a resin filled hole with a screw thread insert which makes it easy to fix it to either the case or PCB for smaller units which can also be PCB mounted by threading thick wire through the and soldering it to the PCB but make sure there's not electrical contact between either ends of the wire.

Rhythmtech:
Your question is kind of a generalized design question.  If the question were contextualized in terms of application and maybe which two transformers you were looking at, it would be easier to give a good answer. If one were always better than the other in every application out there it wouldn't make much sense to keep both designs around right? Conversely if the stand iron core is 1/10th the cost and would do your application just well as the toroidal then why pay more or vise versa... Picking out components is a lot more fun than just "which is best."

KTP:

--- Quote from: TechGuy on October 01, 2010, 06:10:32 pm ---
60/50 hz transformers use laminated plates whether they are toriod or e-core. Some high efficiency 60/50hz transformers will use tape wound foil instead of plates to reduce eddy current losses

A e-core transformer is a a pair of toriod cores, that are joined in the center. The difference is that all of the winding is in a limit area instead of all around like in a toroid.

Personally I prefer ecore transformers over toriods they are easier to mount and much easier to wind (when I make my own custom transformers). I do use toroid power inductors in non-isolated DC-DC converters, as they are better than rod core inductors, and have good thermal disspation. The only time I would buy a toriod 60hz transformer, is if I couldn't find a compatiable e-core transformer that meet the output voltage and power requirements.


--- End quote ---

hmmm, so why did they go with a toroid 60hz transformer in a medical laser unit I scrapped for optics parts?  It says primary 100-120V 50/60hz 2549VA (really? not 2550?) secondary 206V 2400VA.  I was going to throw it away, but now I am curious what the core looks like...

Unless somebody wants it?  It is about 20 pounds...

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