Are toroidal transformers best?

This is what Onkyo says.........
<QUOTE>
Toroidal Power Transformer

For the most state-of-the-art power delivery available-the custom-built toroidal transformer employed in the TX-DS989 is formed from a single strip of silicon steel, tightly wound in the form of a clock spring and wrapped in copper wire to form a silent, highly stable power supply virtually free of mechanical hum. The use of primary and secondary wiring around the entire core prevents air gaps, reducing magnetic flux, and making this very powerful, high-end unit 40% more efficient than conventional transformers.

High-Grade Isolated EI Transformers

Designed for efficient operation, even under high temperatures, these large transformers provide plenty of power reserves for today's multichannel digital sources.
</QUOTE>

It seems to me that they are saying what everyone else is saying ...... Toroidal Transformers are the best most efficient, lowest noise transformers .........

[Edited by AudioFreak on 11-13-2001 at 04:04 AM]
 

cp642

Member
2001-08-17 6:00 pm
An article that i've come across states that a properly designed and wound EI core transformer beats an off the shelf toroid anytime, but at a cost.

My personal experience with EI core transformer has been somehow dissapointing so if you should ask me I'll opt for a toroid instead......
 
this maybe true, but if you are going to get a custom EI core transformer of course the stats will be better ..... if u compare a custom EI core transformer with a custom toroidal transformer then things start to even up again but with the greater efficiency of toroids and less stray flux .......

personally i use custom built toroidal transformers .....
 

cp642

Member
2001-08-17 6:00 pm
just a thought............

" I keep saying "theoretically" as whether and to what
extent this will be true greatly depends on both
transformer materials and equally to its winding. If wound properly, so that a secondary ends on the spot where
it begins, if good quality rings are used and if good quality wire is used, then it will display all of its benefits to a considerable degree. In practice, unfortunately, I have seen far too many toroidal transformers which were poorly made, despite bold manufacturer claims.

Actually, you can check up on this rather easily. Using all necessary safety precautions, connect the transformer
to the mains, then connect your multi meter across the secondary and measure its quiescent current
consumption (the current it uses up with no load). Remember that by default, larger capacity transformer will use
more current than a smaller one, and in all cases, you are in the milliampere range, below 30."
------------------------------------------------------------

I was wondering how true this is......testing the quiescent current of a transformer??? For the full story check out http://www.tnt-audio.com/clinica/ssps2_e.html
 
I've seen arguments pro and con for both EI and toroids. I wouldn't get too hung up on the point, myself. About the only reason I can see for really getting worked up is that toroids are somewhat less prone to interference. Even then, it's not that difficult to shield a transformer or, better still, arrange a remote power supply. Fringe benefits include getting any RF spray from the rectifier out of the way and more freedom to configure the circuit mechanically in a manner that suits you.

Grey
 

rlg_200

Member
2006-09-04 2:08 am
EI or laminated transformer is mostly use in power distribution, The advantage of this transformer is easy to mount and easy to wind. but if you consider the power efficiency EI is not efficient. toroid is more efficient than EI it is especially used in audio and computer electronics. beacause of high efficiency and free for magnetic interference.
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi cp642,
Actually, you can check up on this rather easily. Using all necessary safety precautions, connect the transformer
to the mains, then connect your multi meter across the secondary and measure its quiescent current
consumption (the current it uses up with no load). Remember that by default, larger capacity transformer will use
more current than a smaller one, and in all cases, you are in the milliampere range, below 30."
And it's new meter time! I read this as you hanging a meter set to mA across the secondary. Poof!

What you meant was, measure the primary current with all secondaries unconnected. This, of course, should only ever be done by a qualified technician as you are directly on the mains now.

-Chris
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi walker,
Unless you need the low form factor, or are running off 400 Hz avionics power, an EI core is best in the real world. They are less expensive to buy and the air gaps can help with common power line issues. Core saturation is a bigger problem with toroids. Not to mention the have poorer high frequency response, and that is what you want. You do not want to pass the high frequency hash too!

-Chris
 
This is a very old post that I put out to see if there was anything new under the sun. It appears not.
The task of the power transformer is to provide a low imedance voltage conversion, not to filter noise. Much of the information that has been published by manufacturers is marketing hype
wanting to convince buyers that cheaper transformers, (EI core) are better than torriodal transformers. If you buy this marketing hype they can sell a cheaper product at a greater price.
If you have noise problems filter it or better still isiolate it.
The core saturation argument makes no sense to me. If you get a power spike I'd rather have the core saturate to keep the sike out of the secondary rather than attempt to pass it on. The EI core will still EFFECTIVELY saturate as the leakage flux increases during a voltage spike.
Using a multimeter to read the magnetising current in the primary will not tell you how reactive the current is and therefore is of little use either.
Both transformers work well, but the torriodal has better supply regulation and lower stray flux. As I see it still the best choice.
Regards Walker
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi walker,
I can see this popped up again. Amazing.

I disagree completely with you with regard to the frequency response and saturation aspects, but that's okay. It is your opinion however, it's only fact to you. There are pros and cons to each type.

Using a multimeter to read the magnetising current in the primary will not tell you how reactive the current is and therefore is of little use either.
That tells you what the magnetizing current and eddy losses are to the best of my knowledge.

A toroid has poorer heat transfer than an EI core. So you can use the chassis more efficiently to cool an EI core that is exposed.

So, on my planet, an EI core rules unless I need something flat. ;)

-Chris
 
Frequency response

One post made reference to the frequency response of the Transformer.
Now all things being equal there are differences in the frequency responses of the transformers, however things are not equal here.

EI cores and toroide cores are not commonly made out of the same core material

EI and toroid winding depths are very different due to the construction process.

EI and torroids have different core coverage percentages.

All this means that we are comparing apples and oranges.
Sure they are both fruit, but they are very different.


Brian
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Hi Brian,
We are comparing the performance of the finished, average product. It is not an apples to oranges comparison.

You are correct about core material, but if you can compare a Ford Mustang to a Chev Camero or Corvette, you can compare the performance of two different constructions of power transformers.

-Chris
 
walker said:
The core saturation argument makes no sense to me. If you get a power spike I'd rather have the core saturate to keep the sike out of the secondary rather than attempt to pass it on. The EI core will still EFFECTIVELY saturate as the leakage flux increases during a voltage spike.

The problem with saturation referred to is one of small DC component present in the AC network. This will more readily and asymetrically saturate a toroid or R-core transformer than any other type because they don't have an airgap. At that point one may get unexpectedly high levels of stray flux and hum from a transformer type that should be immune to it.
 

rdf

Member
2004-06-21 8:04 am
big smoke
ilimzn said:


The problem with saturation referred to is one of small DC component present in the AC network. This will more readily and asymetrically saturate a toroid or R-core transformer than any other type because they don't have an airgap.

My brother in Ottawa has this problem with torroids connected to the local utility. Enough DC is present to make them buzz constantly.
Like most of these "which is best"-type questions the correct answer seems to me: "best for what?"
 
anatech said:
"C" cores anyone? They seem to offer advantages of both types.

Yes, I like them very much :) but they are still larger than a comparable toroid. I have recently had some toroids custom made and had extensive talks with the manufacturer - and learned that there are indeed gapped torroids! In fact, you could think of this as 'round C-core' transformers - the core is glued together and the windings wound the same as a regular toroid. There are also C-cores that can be wound that way assuming the cores are fixed together.