Tony's latest traffo DIY build

..................may i ask you in using series bulb test to a newly made traffo, what would be the necessary wattage of the bulb?
is it ok to apply series bulb test after winding the primary coil only?................

you use the series lamp tester on a completed traffo for EI...
wattage of lamp is not so much a big deal, i use 100 watts in mine...
the primary only test is OK.
you can use the bulb resistance to limit the current so that a too few turns primary does not get damaged.
You can measure the voltage across the primary and measure the voltage drop across an in series 10r resistor to determine the current. From that you know the Henries and what to expect for that particular Vprimary.

I use a low value bulb wattage for transformer alone. Typically 25W or 40W. Often this value does not even flicker. The transformer just turns ON.

Once that is complete you can progress to using a Variac to check Iprimary for the full range of Vprimary and then plot Vprimary vs Iprimary and see the "S" shaped curve and decide if the highest Vac is getting too close to saturation.
This can all be completed before you wind on the secondaries.
 
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is it ok to apply series bulb test after winding the primary coil only?................

only if you put the iron cores first and then you test,
after that you will need to take the cores out again and wind
the secondary winding...
i am not sure you want to do this....
nor do i understand why you would want to use a lamp tester on the primary coils only, when a dmm can test for dc resistance...
you can do the test with primary only windings on a toroid
because you have the cores as coil formers...
it is different with an EI...
with a lamp tester, the bulb is dim and the degree of dimming is directly proportional to the magnetizing current,
more current and the bulb glows more, and vice versa....
a fully lit bulb indicates shorts in the secondary or primary...
 
the primary only test is OK.
you can use the bulb resistance to limit the current so that a too few turns primary does not get damaged.
You can measure the voltage across the primary and measure the voltage drop across an in series 10r resistor to determine the current. From that you know the Henries and what to expect for that particular Vprimary.

I use a low value bulb wattage for transformer alone. Typically 25W or 40W. Often this value does not even flicker. The transformer just turns ON.

Once that is complete you can progress to using a Variac to check Iprimary for the full range of Vprimary and then plot Vprimary vs Iprimary and see the "S" shaped curve and decide if the highest Vac is getting too close to saturation.
This can all be completed before you wind on the secondaries.

thank you for your reply sir,
now i can appreciated how sophisticated the technical data was in making traffo since i learned mostly only from google about this thing.
mine is very conventional i used to wind traffos that after the primary turns i used 50watt lamp that whenever this lamp will no longer lit up, to ME means there's enough turns that core can handle, some call it solenoid.
that is the time i wound the secondary equal to the primary i.e. if my primary was #17 @220v mains. then i will use #13 @45-045AC as secondary. my usual EI cores used CL 1.5"/2" will stack to 4"-6"

i was not particular with your terms but now i will use it as a guide for learning more about this traffo.

thank you so much
regards
sam
 
only if you put the iron cores first and then you test,
after that you will need to take the cores out again and wind
the secondary winding...
i am not sure you want to do this....

yes sir i do that not as fit/fix as final because i cannot rely sometimes the type of core available in the area.
my experience 1.2-2.2 turns/volt i have used several formula but non of them work all the time so i counter check with bulb.

thnks
sam
 
H50 is the cheapest and widely available core that can be purchased new....
otherwise, when using surplus cores from torn down equipment,
you will more or less know about its quality by its thickness, noss are almost always 0.5mm, better quality steel are 0.35mm thick...

when i am not sure of quality of steel, i assume it as H50...
 
here are some of my work
 

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I think, in general stacking laminations to extended heights like these may not be too desirable, due to increased winding lenghts.

Best regards!

agreed, and the next bigger core is selected, the ideal is a square, but rectangles with a ratio of 1:3 is usually my limit....

but when you come from a country where resources are limited, then this will do....

i tell local guys that for as long as you know the consequences of one's choices, then you can do it in any geometry you like....
 
A ratio of 1:3 seems quite a lot to me. Here in Germany, maybe in continental Europe also, standardized cores, i.e. those with pre-fabricated bobbins, are/were stacked to not more than 1:1.5.

Best regards!
for good use of the iron the core should be roughly square.
1:0.7 to 1:1.5 would be a good range that gives acceptable use of the iron core.
1:1, or very close, gives best use and also allows the optimum window for copper.
As the ratio is stacked longer, the copper window remains the same but the iron limited VA is going up and the copper length is going up. These two effects increase the transformer regulation and lead to a big sag in voltage as the load current is increased.
It would be better to select a wider/bigger EI for improved transformer performance and probably end up lighter and cheaper and lower regulation due to less iron and less copper length for the new bigger VA.
 
As the ratio is stacked longer, the copper window remains the same but the iron limited VA is going up and the copper length is going up. These two effects increase the transformer regulation and lead to a big sag in voltage as the load current is increased.

Did you really want to say this? I think transformer regulation is decreased this way, leading to an increased sag.

Best regards!
 
Vout at zero load current and Vout at rated load current give the transformer regulation.
Regulation = ((Voutzerocurrent/Vout@ratedloadcurrent)-1)*100
Transformer regulation is a measure of how much the voltage increases as the load goes to zero amperes.

If you have a bigger core area allowing a higher VA, then you have an increased rated current.
But if arriving at that increased current you have used the same window area requiring the same copper turns and the same copper area, then the copper resistance will have gone up due to the increased length of every turn. The increased resistance at the higher VA and higher current will give a higher sag in voltage (or a bigger difference between Voutzero current and Vout@rated current).
i.e. regulation has gone up.
 
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Wouldn't have expected that increased regulation means worse regulation...

Best regards!
A 4% regualtion transformer has the unloaded Vout @ 104% of the rated Vout
whereas a 7% regulation transformer has the unloaded Vout @ 107% of the rated Vout.

i.e. off load the 7% regulation transformer has a higher voltage.

Where this can become really troublesome is when running some component at near it's maximum voltage rating and the mains voltage increases to maximum allowed. A small transformer with a high regulation can break the component due to the very higher off load voltage.
Very small EI transformers can get regulation up around 30% !