We are installing some Altronix power supplies for surveillance cameras. They have toroidal power transformers in them - each about 5 or 6 inches across (125 - 150 mm). They look pretty nifty, but all of us are wondering "why a toroidal transformer?"

What advantages do these have over the E-core power transformers?

 

I'm no expert, but I believe they have less stray magnetic fields and are smaller for the same rating EI tranny.

Oh, hey, lookie here!

 

Toroidal transformers are more efficient than isolated core (normal EI core) ones. This happens to be since the secondary winding covers the primary winding completely, and without being far from the core either. Thus, the magnetic field is shielded (completely absorved) by the secondary.

 

They are easier to mount, as well. The ones I use have an epoxy fill in the center with a hole left open. It's just right for a 10-24 tap. besidee that, the transformer is more compact that an E core equivalent, so mounting options are greater.

 

what about eddy currents ,are there any laminations?
else they may heat up easily.

 

what about eddy currents ,are there any laminations?
else they may heat up easily.

I think, torroidal transformers are wound on ferite torroid core. Ferrite doesn't conduct, so there are no eddy currents.

 

...else they may heat up easily.

Actually they will heat up less easily than conventional ones since they dissipate the heat better.

 

if so much goes for the toroidal ones and against the conventional ones i wonder why i havent heard big companies using these designs for power transmission.
maintenance of a generator transformer and others as well is a big problem and their replacement sometimes takes months to transport etc.


can toroidal ones be three phase?

 

Ah.Power transmision requires very good insulation, I.E. from 11Kv down to 240 volts for your domestic supply.....There is difficulty fitting such large amonts of insulation on a toriod, so transformers for this application are usualy built using seperate bobbins, and are then immersed in oil.I think you will also find that only high frequency toriodals are wound on ferite cores.....One disadvantage with toroidals is the larger surge at switch-on, but other than that, yes they are more efficient and produce less stray magnetic field, and of course if you are dealing with equipment built in 1U rack cases, they fit !!!.....One thing to look out for if you are using them in narrow (metal) enclosures, is that you DO NOT mount them using the bottom and top bolts together as this is in effect a shorted turn....Daniel.

 

...One thing to look out for if you are using them in narrow (metal) enclosures, is that you DO NOT mount them using the bottom and top bolts together as this is in effect a shorted turn....Daniel.

A very good explanation, but I do not quite understand the last sentence. Short turn? Please explain me.

 

The bolt through the center connected to the top and bottom of the case then forms an electric path.

The bolt becomes in effect a wire wound from the center around the outside and shorted together.

And it's best in many cases to use non-metallic hold down hardware.

 

We use them at work in controller boxes primarily because of their thinner profile. We call them 'pancake trannies'.

 

The bolt through the center connected to the top and bottom of the case then forms an electric path.

The bolt becomes in effect a wire wound from the center around the outside and shorted together.

And it's best in many cases to use non-metallic hold down hardware.

It is like a third coil, right? Or is it more an isolation fault caused by ruptures in the isolation made by a too tight bolt?

 

It would in effect be another single loop winding on the transformer that is shorted. YMMV on what effect that has on it.

Your Mileage May Vary = Colloquialism meaning my answer cannot be or is not precise.

A related effect on standard transformers is having a coil or coiled wire near them. Depending on what the coiled wire goes to you can have exceptional amounts of fun trying figure out WTF is going on. In my case some other 'teak knee shun' had spliced a 'gob' of wire into the video circuit of a TV and taped the excess to one of the switching transformers.

It is like a third coil, right? Or is it more an isolation fault caused by ruptures in the isolation made by a too tight bolt?

 

It would in effect be another single loop winding on the coil that is shorted. YMMV on what effect that has on it.

YMMV? I don't understand. I'm not familiar with suck anagrams.

 

YMMV-your mileage may var-you may get different result due to different random factors.try some googling.

 

An related effect on standard transformers is having a coil or coiled wire near them. Depending on what the coil coiled wire goes to you can have exceptional amounts of fun trying figure out WTF is going on. In my case some other 'teak knee shun' had spliced a 'gob' of wire into the video circuit of a TV and taped the excess to one of the switching transformers.

I routed my output cables from the corners of the boxes opposite the transformers. Service loops are in the fingerduct between boxes. I'm told the aiming & focusing crew reported no problems with our installation.

 

I'm really not sure what frequency the power supply was running at anymore. It was the video drive in a projection television to the green tube and it cause the most bizarre interference pattern. Why it got hacked and replaced is anyones guess.

Cutting the 'gob' of wire out and splicing in better quality wire, using a better splice and heat shrink tubing then routing the results per specification fixed it. I was trying to avoid the delay in acquiring and the expense to the customer of a replacement harness.

Since my company was Sony authorized and I suspected I could get a deal for the customer I contacted our rep and told them about it. He sent a form and the needed part and we were able to refund our customer their money and do a complete repair and Sony reimbursed us. I'd only charged the customer the service call. Sony paid us three times that.

Ah, memories. I no longer do that type of work.