Once upon a time in Romania

In this hobby we talk a lot about the importance of power in audio systems, from power cables to power conditioning, power cables, power regenerators, power sources, transformers, etc.

I’ve even seen transformers with the core made out of pure silver cables with some extreme prices on them. Sometimes I think of doing a little DIY, but I lack the time and experience in this domain.

Thinking about this while talking to my father one day, I’ve managed to drive the subject in a very fruitful conversation from which I’ve heard a great story from my father’s childhood, a story that showed the great educational system Romania had in that period.

The story is about how he manufactured a transformer in the eighth grade. I always loved to apply theory in practice, as I think it is the best and most fun way to learn, something we rarely do nowadays, but they did it right in the past.

I actually went to the same high school as my father, the oldest one in my birth-town, as it was opened in 1883.

Liceu

 

And a more recent picture:

 

Spiru Haret

 

I loved the story so much that I asked him to write it down so  I could share it here even if it may be a little off topic.

SCHOOL MADE – ELECTRIC TRANSFORMER

 

It was a time, when the children in the primary, gymnasium and even in the high school had lessons on tailoring and cooking for girls; carpentry, mechanics,locksmiths, electrical and electronics for boys.

We were trained for basics skills in these activities, in order to learn how to do easy things like sewing a button, cooking something light or cookies, repairing the lock of the door or dismantling a mechanism like a laundry machine, changing the iron resistance, repairing the lightning or electric cables or device.

Besides that, we went even further to a level where we learned how to manufacture a mechanic, electric or electronic device.

I remember that it was in the eighth grade when we had in our curriculum the first electrical and electronic lessons…

One of the activities was to learn how to design and manufacture the electric transformer…

Maybe this might not interest you, but for us it was challenging, because the professor was giving each pupil the task of designing an electric transformer with individual and specific parameters, a transformer with utility for  the future lessons.

At that time it was impossible to find a transformer on the market or one that was already built by another pupil. There was no google, no internet, no e-commerce!

My transformer’s purpose  was  spot welding, therefore the transformer’s power should be as high as possible so it can be used in home electrical network i.e. 2.200 – 2.500 kW and low voltage and high amperage.

The spot welding is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current.Work-pieces are held together under pressure exerted by electrodes. Typically the sheets are in the 0.5 to 3 mm thickness range. The process uses two shaped copper alloy electrodes to concentrate welding current into a small “spot” and to simultaneously clamp the sheets together. Forcing a large current through the spot will melt the metal and form the weld. The attractive feature of spot welding is that a lot of energy can be delivered to the spot in a very short time (approximately 10–100 milliseconds) that permits the welding to occur without excessive heating of the remainder of the sheet.

The amount of heat (energy) delivered to the spot is determined by the resistance between the electrodes and the magnitude and duration of the current. The amount of energy is chosen to match the sheet’s material properties, its thickness, and type of electrodes. Applying too little energy will not melt the metal or will make a poor weld. Applying too much energy will melt too much metal, eject molten material, and make a hole rather than a weld. Another feature of spot welding is that the energy delivered to the spot can be controlled to produce reliable welds.

We needed to find copper wire at the specific diameters, to find the materials for the transformer’s magnetic core, to manufacture the wiring house.

So, after the theoretical presentation of the basic electrical transformer and the calculations of main parameters, starting from the destination of this device and in what application we will use it,  we calculated the level of voltage, intensity of each secondary output  and then the transformer’s power.

And then… of course, now everybody can find on the web thousands of software to calculate in very details the electric transformer and even to purchase it, but 35 – 40 years ago, were just books, professors… and a lot of imagination!

Well, after all these calculations were ready and verified by the professor, we started the manufacturing!

Well, let’s find the wiring housing – copper wires, glue, etc. from the store. The professor gave general explanations on how to design and manufacture the transformer’s winding housing. I remember that everyone repeated at least two times this exercise until we got something that was accepted to be the transformer’s winding housing.

But what about the transformers core sheets ? Where could I get something like that?

OK, let’s use the imagination! I was living in Tulcea, city on Danube River close to Danube Delta. One of the main activities in 70’s and 80’s was fishing on Danube and in it’s Delta. Other activities came attached to fishing, like fish food industry with all its necessary chains like can manufacturing, vegetables lands, industrial fish cooking systems and canning, storing and delivery.

This was before the ocean fish industry began to take over. So, in the in 90’s Romania counted more than 60 sea fishing ships and 11 fish collecting ships. Now we are importing fish canned from everywhere!

But, coming back to my transformer I needed to find something to be used as transformer’s core sheets.

Well, I remember that we used to go in the can factory to take some long and narrow metal sheets (tin plate – which was used in the manufacturing of the cans) the remaining part from the can’s forming press, material we used  to manufacture swords and shieldsJ for children’s games!

can factory tulcea

Can I use these sheets for transformer core?  Why not?

can factory tulcea 1

The tin plate has 0.3-0.5 mm thickness and has a protective paint on both sides that was good for cutting the electrical currents generated by the magnetic field inside the transformer’s core that keeps down the temperature of the core at normal values.

The next steps were to select the required dimension and to find the right amount of sheets and to cut them at required dimensions. For the welding transformer at that power, you can imagine that the cross section of the magnetic core is quite big; therefore I used the tin plate of 50mm wide and the 150mm length that made a very heavy transformer.

The professor has approved the idea, with only one tip – to increase by 10% the core surface, in order to compensate the magnetic quality of the metal (normal I shall use ferromagnetic sheets design for transformer’s core). Other few kilos to be added to the transformer.

It had more than 15 kilos and after I put the welding equipment above, more than 25 kilos. I was difficult to handle it, but …!

The wiring I made using thick copper wire of 3mm for the primary coil and 5mm aluminium for secondary coil, purchased from one discount shop for materials – I was lucky because they were quite cheap and I was afforded to spend some money.

Because the wires I used were thick it was quite easy to bobbin, having no problems with coil arrangements, with coils counting etc. but difficult to handle the wiring housing with copper and aluminium coils, aligning the wires and counting then – few hundreds for primary and few tens for secondary.

The ones who had to manufacture low power transformers with thin copper threads had to wire thousands of coils for the primary and a few hundreds for the secondary.

After manufacturing the housing and wiring the primary and secondary, we had to assemble the core, sheet by sheet, in one specific way, in order to respect the dimensions of the core and to avoid any gaps between the tins.

The testing consisted in connecting the transforms to the electrical network and … measuring the secondary parameters – voltage and then amperage.

How many transformers did we burn? Not even one!

It is true that we had some transformers that overheated or some that were not functioning due to the bad wiring of the fine cupper thread – this was the bad news for us because we need to rewire the whole transformer again and … again …

My transformer was working very good, but was noisy due to its size, therefore I had to tight the magnetic core with some bolts!

At the end, all of us made a good job and got good grades and a tremendous experience in using theory, life experience and handy craft practice!

Hmm…that is a very cool hobby to have as an eighth grader and I must say that they learned some very interesting stuff back then at that age. I wonder what activities have the eighth graders these days and what do they learn at school? Actually I have an idea about what they learn and it is not nearly as fun and practical.