[Vintage Sounds]

I noticed every dry-type distribution transformer out there seems to be the EI type. My question is, why aren't some of these transformers toroidal style? Toroids have mostly replaced EI transformers in electronic gear.

I'm not a transformer expert but from what I've read about them, they are smaller, lighter, require fewer turns of copper, have fewer losses and radiate less EMI. The only drawback appears to be higher inrush current because there's no air gap in the core. Also it looks like larger sizes are harder to accomplish.

Something like this, but built into a cabinet.

http://www.powertronix.com/3_phase.php

I even found a company that makes toroidal control transformers.

Is it cost, or convention?

 

[8V71]

Maybe the labor involved in threading the entire length of wire each time through the hole of a large kva transformer?

 

[CADPoint]

To answer directly, I don't know.

What I do know, that about five years ago that a new company came out
with higher grade copper and generally better metal properties all around; thus
creating what your seeing as a sudo new line of products.

 

[micromind]

I'd say inrush current. A basic transformer has an initial inrush so high that it very nearly trips a breakers instantaneous trip unit.

I'm pretty sure that the majority of breakers would see the inrush of a toroidal transformer as a fault and trip.

 

[uconduit]

I think it has a lot to do with the frequencies. Most toroidal transformers in electronics are part of smps's and the frequency is like 44khz or something. But I admit I don't remember exactly why.

 

[oliquir]

cost!!! a toroidal electronics xfmr cost 2-3 times the cost of a normal xfmr. ive used double wound variac (isolated variac) made with toroidal xfmr from india for a custom project (i know not UL listed), i dont know how the made them, but surge current is not very high and efficiency is very high
http://www.radioelectricindia.com/