0.35mm are already good in my book, better than 0.5mm ones...
if i am am unsure of steel quality, i treat them as lowest quality steel, H50.....
this way you are safe from saturation issues under heavy loading...
if i am am unsure of steel quality, i treat them as lowest quality steel, H50.....
this way you are safe from saturation issues under heavy loading...
IF you want to measure in a somewhat indirect but very practical way, and you have a Variac, wind a primary nominally suitable for, say, 120V , insert laminations under test, apply, say, 20% less so 100VAC and measure idle current.
No secondaries needed and obviously no load.
Then start rising voltage in 5% or 10% steps, your choice, always monitoring current.
At a certain point iron will approach saturation and current will start to rise way more than voltage applied increase.
Repeat with the other lamination.
You will have 2 useful results:
1) how much does your lamination really stand, and in more precise way than crude "feeling overheating".
2) whether they are basically the same or not (so far it looks they are different):
I didn´t suggest it before, because you were talking recycling 2 old transformers, and for "experiments" , no critical use; but now you are talking hundreds of kg , hundreds of Euros, long travels, ... situation changes 🙂
Note: why do I suggest a "useless" 120V primary?
Because living in Europe, available Variacs for you will probably reach 250/260V tops and you might still be far from saturation point; with a "test" 120V wprimary you will *definitely* reach saturation point and beyond 😉
No secondaries needed and obviously no load.
Then start rising voltage in 5% or 10% steps, your choice, always monitoring current.
At a certain point iron will approach saturation and current will start to rise way more than voltage applied increase.
Repeat with the other lamination.
You will have 2 useful results:
1) how much does your lamination really stand, and in more precise way than crude "feeling overheating".
2) whether they are basically the same or not (so far it looks they are different):
I didn´t suggest it before, because you were talking recycling 2 old transformers, and for "experiments" , no critical use; but now you are talking hundreds of kg , hundreds of Euros, long travels, ... situation changes 🙂
Note: why do I suggest a "useless" 120V primary?
Because living in Europe, available Variacs for you will probably reach 250/260V tops and you might still be far from saturation point; with a "test" 120V wprimary you will *definitely* reach saturation point and beyond 😉
Your suggestion JMFahey is quite intelligent and easy to understand. I will test this way🙂.
Sure - things changes as I get more input but 100's of kilos is a bit of an exaggeration 😉.
Regards
Sure - things changes as I get more input but 100's of kilos is a bit of an exaggeration 😉.
Regards
You could test the two types of laminations.
Wind up a primary coil to fit the lam core.
Insert one set of lams and plot the Ipri vs Vpri curve.
Then swap to the other lams and plot the curve.
Compare curves.
This is what JMF is suggesting.
I have plotted a number of smaller and larger 230Vac transformers and all can be seen to start saturating before 255Vac. Some get to very high Ipri by the time I get to 260Vac.
All show the typical "S" curve expected with iron cored transformers.
It was based on these experiments that I suggested some years ago that adding 20 Turns to the primary of a toroid makes a big difference to the idling currents.
Wind up a primary coil to fit the lam core.
Insert one set of lams and plot the Ipri vs Vpri curve.
Then swap to the other lams and plot the curve.
Compare curves.
This is what JMF is suggesting.
I have plotted a number of smaller and larger 230Vac transformers and all can be seen to start saturating before 255Vac. Some get to very high Ipri by the time I get to 260Vac.
All show the typical "S" curve expected with iron cored transformers.
It was based on these experiments that I suggested some years ago that adding 20 Turns to the primary of a toroid makes a big difference to the idling currents.
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Good idea.
It will also help reduce the dreaded "Toroidal Transformer turn on current peak" which sometimes demands adding an NTC thermistor in series, or needlessly increasing fuse rating just to avoid the so called "nuisance blowing" ... while ading a few extra turns is the most direct solution. 🙂
It will also help reduce the dreaded "Toroidal Transformer turn on current peak" which sometimes demands adding an NTC thermistor in series, or needlessly increasing fuse rating just to avoid the so called "nuisance blowing" ... while ading a few extra turns is the most direct solution. 🙂
Sadly, in my humble experience lots of toroid manufacturers seem to wind their products very close to the edge, in order to maximize profit. You'll have to specify, and sometimes to insist heavily, if you don't want them to do so.
Best regards!
Best regards!
11th is Tuesday, i.e in the middle of the week. Cologne is about 350 km from here. I'm living in Southern Germany. If you may want to rearrange your trip to commit at a weekend and to pay my fuel costs (about € 50), we might meet there at a location yet to specify.
Best regards!
Sorry Kay. It was a long shot - no need to jump into the car 🙂. I didn't know where you live so I just proposed one place where we will stay over the night. I don't expect I can persuade my wife to spend days in Cologne waiting for some metal pieces 😉.
I'm out as they will be to expensive 🙁.
Regards
I'm out as they will be to expensive 🙁.
Regards
All ok here, Turbon 😉!
I'll buy all the sheets, magnet wire in different diameters, isolation materials, bobbins - and last, but not least, a winding machine 😀.
Surely I'll find usage for most of the laminations, as I'll yet need about 250 pc. of EI96s and abt. 350 pc. of the EI120s for the 2 x 2 transformers for both my two Philips EL6425 amplifiers.
Best regards!
I'll buy all the sheets, magnet wire in different diameters, isolation materials, bobbins - and last, but not least, a winding machine 😀.
Surely I'll find usage for most of the laminations, as I'll yet need about 250 pc. of EI96s and abt. 350 pc. of the EI120s for the 2 x 2 transformers for both my two Philips EL6425 amplifiers.
Best regards!
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