Is there any difference in using a large Torroid Transformer instead of an Old-Fashioned Square Metal Cased as long as Voltages and Amperages are the same.????

 

Yes, it is likely smaller and costs more. Not sure if efficiency, leakage etc is better.

 

A toroidal transformer has a smaller magnetic field radiating outward to interfere with other circuits. That is why they are preferred in precision audio gear.

Second paragraph:

https://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers

ak

 

IOW, they are much more efficient, less turns/volt etc.

 

Is there any difference in using a large Torroid Transformer instead of an Old-Fashioned Square Metal Cased as long as Voltages and Amperages are the same.????

Yes!!!!

 

Maybe. It depends on the application.
Toroids have more magnetising inductance and less leakage inductance, and lower core losses but that is most likely due to their cores being made out of thinner grain-orientated steel laminations.
Bobbin transformers have more mass, which means that they will withstand overloads for longer without overheating.
Suitability for audio is much more debatable:
True - toroids radiate less magnetic field
But their lower output impedance (lower winding resisitance and lower leakage inductance) create much larger pulse currents in a standard rectifier-capacitor circuit, which can also lead to hum in the audio circuits.

 

If the materials are different and I suspect it is likely that they will be, then you should expect differences in performance. Your question would be more precise if the two geometries were made of the same material. I must confess that I have never seen an iron toroid, nor a laminated square ferrite.

ETA: Apparently they make toroids from laminated iron, iron powder, and ferrite. I guess it would be possible to compare the two geometries with identical materials.

 

ETA: Apparently they make toroids from laminated iron, iron powder, and ferrite. I guess it would be possible to compare the two geometries with identical materials.

For 50hz/60hz, thin silicone steel sheet rolled into a coil is used as the core.
One precaution is that any centre retaining bolt is not affixed to the top & bottom outer case, if fitted, IOW, short-circuit turn.

 

One thing is certain which is that with a torroid transformer there is more chance for he winding to be damaged accidentally, if adequate protection is not provided. And certainly mounting one safely takes more effort and materials. YES, they can be mounted with "just one bolt", BUT there also needs to be adequate insulation provided to avoid accidental connection to the mounting surface. AND, if the assembly with a toroid using a one bolt mount is dropped, there is a greater chance of serious damage. So there is always a trade-off.

 

All the ones I have purchased have supplied the correct mounting HW, if this is followed as supplied , then all should be well.

 

Thank you so much for your inciteful replies, people!!

 

All the ones I have purchased have supplied the correct mounting HW, if this is followed as supplied , then all should be well.

I have not purchased one, and so I am not familiar with whatever hardware those may come with. I HAVE SERVICED AND REPAIRED equipment that utilized toroid transformers,and observed that inadequate retaining strength has lead to serious damage from rough handling.
Your results may differ.

 

Is there any difference in using a large Torroid Transformer instead of an Old-Fashioned Square Metal Cased as long as Voltages and Amperages are the same.????

Hi,

Yes, to start, one is round and the other is square. That's quite a difference

There are quite a few differences, some favor the toroid and some favor the regular steel laminations.
1. A toroid is harder to wind. You can get a machine to wind one, but it's expensive. Laminations are easier in this regard.
2. A toroid is hard to gap. You really need precision machining to get it right. Many of these designs are done by the manufacturer that makes the toroid so you don't have to do it. The down side is that you have to know exactly what you need before you order.
3. You can get distributed gap toroids, you can't get that with laminations, but then laminations are easier, much easier, to gap and you can change the way you make the stack (butt stack, interleave 1x1, 2x2, 3x3, whatever).
4. Once you have a toroid design and you get it made, it's not easy to use in another application because it is usually a custom thing made for one product. Laminations are very flexible in this regard, you can stack more or less, make the gap larger or smaller, etc.
5. Laminations have to be bolted together or welded, toroids do not. It's almost mandatory that laminations have to be vacuum varnished but sometimes toroids only need external high temperature tape. The frequency will be a factor here too though.

On the comical side:
6. You can throw laminations like frisbees, you can't do that with a toroid. This may sound funny, but I once lived next to a defunct machine shop that made steel laminations for transformers, and they discarded a lot of them into an open field. As kids would be kids, we found boxes and boxes of them and had some fun seeing how far we could throw them. As I recall there must have been 100 boxes of them each box maybe 18x12x8 or something, so there were a LOT of laminations just sitting around getting rusty in the open field in the cardboard boxes. Must have been worth a fortune, but most of them were already rusty as they had been sitting there for a long time (maybe two years). It was loads of fun though

There are many other types of cores though too. We have the "Pot Core", the "C core", etc. They are easier to wind also because they come in two halves. You can gap them the same way as with laminations too. You can get Pot Cores with a gap inside while the outside has no gap, which helps to keep the field inside the construction better and outside fields outside of the construction.

 

I am referring to those that modify the mounting so that the centre bolt touches, or is attached to both top and bottom of any metallic enclosure, This then results in a Shorted-Turn condition and produces heat, I have seen in done in a couple of forums.

 

4. Once you have a toroid design and you get it made, it's not easy to use in another application because it is usually a custom thing made for one product. Laminations are very flexible in this regard, you can stack more or less, make the gap larger or smaller, etc.
5. Laminations have to be bolted together or welded, toroids do not. It's almost mandatory that laminations have to be vacuum varnished but sometimes toroids only need external high temperature tape. The frequency will be a factor here too though.

The Mains toroid's I have used, have always been made my coiling of the thin metallic core, IOW they are one continuous piece??

 

I am referring to those that modify the mounting so that the centre bolt touches, or is attached to both top and bottom of any metallic enclosure, This then results in a Shorted-Turn condition and produces heat, I have seen in done in a couple of forums.

We used to use nylon hardware because even when the bolt was through the core and not touching anything else, eddy currents would heat it up and that led to inefficiencies.

 

The Mains toroid's I have used, have always been made my coiling of the thin metallic core, IOW they are one continuous piece??

Oh that's interesting. The ones I used were always molded with some kind of magnetically active material.

Some of the C cores I worked with were made with layers of thin material, but they were somehow held together to make one solid piece.
I remember they were machined perfectly on the faces, and they retained a magnetic attraction even when the current was removed. I energized one with a current one time and then it was somewhat hard to get the two halves apart even when I turned off the current.

 

For a given number of turns, toroids have a shorter mean turn length.
Shorter wires have lower resistance thus for two transformers of identical ratings, the toroid may have improved load regulation.
By the same token, because there is less wire resistance, turnon inrush current tends to be larger.

 

For a given number of turns, toroids have a shorter mean turn length.
Shorter wires have lower resistance thus for two transformers of identical ratings, the toroid may have improved load regulation.
By the same token, because there is less wire resistance, turnon inrush current tends to be larger.

Hi,

Yeah that's another difference.
For a toroid with small diameter 'd' and area A and a square with same area A (needed for equal cross sections), the square wire length for one turn would be d/4 times more than the wire length for the toroid. That's 13 percent more wire for the square shape core.

We could also look at window area vs magnetic path length.

 

√π same area A (needed for equal cross sections), the square wire length for one turn would be d/4 times more than the wire length for the toroid. That's 25 percent more wire for the square shape core.

We could also look at window area vs magnetic path length.

There’s also o-cores which are much closer to the mathematical toroid, which has a circular cross section.
A square cross sectional toroid has a CSA of D and a turn length of 4D.
A “real” torioid would require a diameter of 2D/√π or 1.13D for the same CSA, but would have a turn length 2√πD =3.54D, a saving of 12%