Will this transformer melt on testing?

[umery2k75]

high frequency wire melting transformer





This is a line frequency induction heating device. The picture you see here, is the primary of the transformer. The secondary side of the transformer is not wire.It's a ball bearing.

This device works on a very simple principle.In the primary side there are large number of turns, the primary side is the cylinder.At the secondary side only ONE TURN is there. The turn is itself a bearing.The square hole in the cylinder is for the iron core that fits into it, to increase the permeability of transformer.
So, a scheme of transformer that has higher primary turn and lesser secondary turns leads to low voltage and high current, which means I^2.R losses, that means secondary will starts to heat up.Here the I^2.R losses is what we want, for the bearing(secondary 1 turn winding) to heat up.

The power is control by a TRIAC, by variying phase angle, the power being delieverd to the transfomer is varied and thereby temperature of the bearing can be altered.The mechanism of this device is simple. I saw in that device there was a Sticker that means, people who has heart device installed in there body, must stay away from this device. I think they must stay away for atleast 10m as I remember. On the other hand, this is a line frequency transformer, so how come this is harmful to people that have artifical clocks fitted in their body that sends signal to their heart to work.The heart device makes the heart work, according to signals.This is a line frequency tranformer working at 50Hz, the only difference is that the secondary is made of 1 turn and the turn is bearing. So, I don't know why it's harmful to such patients. Secondly, I asked somebody that I want to plug in the primary side of the transformer(White Cylinder) only to see anything, I observe. He said to me, the winding of the transformer would quickly melt.
Now if you look at the bottom picture.



I had done such experiment, when I was a kid.Rereing to the first figure. I used to do this by using the Solder Iron Wire. When I power on, the wire burst open from the middle with a blue flash. On those days, circuit breakers were not common and we used to have fuses that were of cement and their wires were made by us.They were reusable fuses.

If you see second picture, such type of circuits with a nail are often given in text books to encourage students and to let them know about the magnetic property that comes into it. I think all such typical example uses the DC power of 9V and it evidently get's it Nort pole and South pole and this whole things begins to react like a magent. I don't know as what would be the behaviour if DC source is removed and AC source is given in.Will nail still be able to attract magnets? If yes, so why don't transformers attract objects like magnets?

If you see the 3rd picture, it's a typical picture for showing about the operation of transformer.If you see the primary is shorted and secondary is shorted. There must pass a huge amount of current when the transformer is in operation, but all such things don't happen, because primary/secondary might have some impedances.Suppose, this transformer is of 220-12V. I can hook up a 12V bulb and energize it, the bulb begins to glow.Primary and secondary is not getting short and no large amount of current is flowing in primary/secondary.If primary is not getting short, so how come when I energize the primary coild with 50hz 220V will get melt, accroding to some one?

 

[FvM]

how to melt a nail with a transformer

Some points are rather unclear in your considerations. Your talking of a line frequency induction heating device. Actually, you won't achieve a considerably induction heating effect at mains frequency without a closed magnetic path. Would be different with a medium frequency (at least several kHz) heating device, as used with an induction cooker.

Also the other examples need some clarification, e.g. the last one:

If you see the primary is shorted and secondary is shorted. There must pass a huge amount of current when the transformer is in operation.

Transformer short circuit current is common problem in electrical engineering. But what do you mean with both windings shorted? When the primary is shorted, no voltage is feed to the transformer - you get no current flow at all.

 

[umery2k75]

can u remove the core from a transformer?

There is a closed path, if you see in the picture.This is how it looks like, when bearing is install in the machine for heating it up.

The heating occurs at line frequency 50/60Hz only and not in Khz. The heating temperature to attain is also some times low. Like maybe bearing would be heating at 130'C and then removed from the device and put it in the shaft or whatever, when the bearing cooils down. It will make a tight grip.I have seen induction heating occurs at 10-50Khz frequency, but this is a line frequency induction heating.

Transformer short circuit current is common problem in electrical engineering. But what do you mean with both windings shorted? When the primary is shorted, no voltage is feed to the transformer - you get no current flow at all.

In normal condition, while the bearing is being heated. We see secondary is of 1 turn, shorted and heavy current would flow through it.



Suppose if I take primary winding, as you can see in the first above picture, what would happen if I apply 220V across it's winding. A person told me, the winding would burnt up. I don't understand why it would burn up. Actually in an industry there were 2 similar machines of this type, that were faulty and were just lying useless in the store room, this machine works, but it's seven segment display panel just don't work, so that's why this unit was discarded. I brought it at home just to do some operation.I have to return this unit too.I want to apply the 220V at it's primary to see, why it's considered dangerous to people with heart devices install in them.I'm thinking of taking this primary side to a some good hospital to know, why a line frequency transformer could be dangerous. A person said, primary would melt. If I add the iron core and secondary too, as in the above picture, then primary will not melt. How would transformer come to know if it has secondary winding or not.

Take this transformer as an example, when I plug it in the primary of the transformer, I will get 12V output at the secondary. Why doesn't primary get's melt? I know there's impedance that's resisting current to flow at higher rate. Suppose if I make a transformer and calculate the proper turns for secondary step down voltage.How will I know that short circuit would not flow in primary and I have proper inductance at the primary side that would limit the current. What is the limiting factor in the transformer, that limits how much current should pass throught it, what do I do, when designing a transformer.

This is the manual of the device

 

[umery2k75]

melt line testing

If yes, so why don't transformers attract objects like magnets?

I have asked the same question to a senior person. He explained me the reason, why transformer don't react like magnets. He said, because magnetic flux is locked inside the loop(iron core). He said, for example. If you take EI type of core. Your primary winding would be at E core and secondary at I core. If you energize the primary side by giving the AC. The secondary side will get induced AC voltage. Now if you remove the core I from EI core, then this transformer will become a magnet. He said, as long as I is attach, magnetism is being converted into voltage, as you remove the I core. The E core will become the magent instantly. More over he added, by using this technique he had done few test and had checked whether the primary winding is healthy or not. He said, often transformer rewinder says in the maintenance shop that, your primary side is burnt up. It need replacement. So he said, I double checked the primary side, by removing the secondary side. If the transformer is working good like a magnet, then this means transformer is good and healthy.

 

[FvM]

installing primary of transformer to secondary

O.K. it uses a core. Couldn't be guessed from the pictures shown before. As I said, some points are rather unclear in your post.

As a common point, you apparently miss some basic understanding of transformer operation, particularly the role of the core. That's the same with the "magnet and transformer" question.

My view on this basic AC magnetics and transformer stuff is ruled by the knowledge of some simple equations, that allow to predict the behaviour of each of your "experiments". Also intuitive insights without much calculations are possible. Most engineers and other professionals in this field have it. The second years experimental physics lecture is a place, where natural science and engineering students can get some of these insights, energy engineering labs are another for electrical engineering students.

P.S.: I overlooked a sentence in your first post.

The square hole in the cylinder is for the iron core that fits into it, to increase the permeability of transformer.

It clarifies, that a core is used, but the explaination is missing the point, anyway. The primary purpose of the core isn't increasing the permeability, it's flux linking of primary and secondary.