post4 lists useful information that will help to safely and non destructively determine if 4Aac is a reasonable value for rated output current..........If you have other ways then voice them and help this guy out.
Weighing it doesn't help much unless you know 1) The material and 2) The flux density used by that manufacturer.
As I keep saying.
Try giving a load.
Try about 0.5A at a time and see how it gets on, both in heat and voltage.
If the voltage starts to drop (more than say 10%) and/or it starts to get warmer than expected, then you have reached a sensible (max) load for that transformer.
If you want to be really delicate you can load it 100mA at a time but that is being overcautious.
The thickness of the Primary winding might be a "red herring" it is the thickness of the secondary winding that really determines the (max) output current.
0.5mm = 25SWG which is about 310mA. 250V x 0.31A = 80VA which is well outside what we are looking at. Obviously different manufacturers use different tables for maximum current but this is the norm. that I was taught in Colledge.
Try giving a load.
Try about 0.5A at a time and see how it gets on, both in heat and voltage.
If the voltage starts to drop (more than say 10%) and/or it starts to get warmer than expected, then you have reached a sensible (max) load for that transformer.
If you want to be really delicate you can load it 100mA at a time but that is being overcautious.
The thickness of the Primary winding might be a "red herring" it is the thickness of the secondary winding that really determines the (max) output current.
0.5mm = 25SWG which is about 310mA. 250V x 0.31A = 80VA which is well outside what we are looking at. Obviously different manufacturers use different tables for maximum current but this is the norm. that I was taught in Colledge.
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As I keep saying.
Try giving a load.
Try about 0.5A at a time and see how it gets on, both in heat and voltage.
If the voltage starts to drop (more than say 10%) and/or it starts to get warmer than expected, then you have reached a sensible (max) load for that transformer.
If you want to be really delicate you can load it 100mA at a time but that is being overcautious.
Thank you KatieandDad.
I really appreciate your help
it is the thickness of the primary winding that determines the maximum input current.it is the thickness of the secondary winding that really determines the (max) output current.
Both limiting values must not be exceeded for continuous operation.
It's your assumptions that are questionable.
0.5mm diameter gives ~0.2sqmm
At 3.1A/sqmm I would suggest that maximum primary current could be around 600mAac
For a 230Vac transformer that would predict a maximum input power of ~140VA and using 94% efficiency gives a maximum output power of ~132VA.
That to me is not meaningless.
Now apply the other data I suggested to see how they tally in predictions.
0.5mm diameter gives ~0.2sqmm
At 3.1A/sqmm I would suggest that maximum primary current could be around 600mAac
For a 230Vac transformer that would predict a maximum input power of ~140VA and using 94% efficiency gives a maximum output power of ~132VA.
That to me is not meaningless.
Now apply the other data I suggested to see how they tally in predictions.
Originally Posted by KatieandDad
it is the thickness of the secondary winding that really determines the (max) output current.
it is the thickness of the primary winding that determines the maximum input current.
Both limiting values must not be exceeded for continuous operation.
both primary and secondary resistance have an effect...but the thing that limits how much power can be drawn out from secondary terminals is temperature and insulation qualities of the traffo, how hot are you willing to go? how high will the temperature be before insulation of wires and bobbins start to burn out or melt?
Hi guys
Sorry for late response and thanks for help
The trafo is -thank god- still alive and it's an E-I ,secondary wire diameter is about 0.5 mm, primary (couldn't see it)
Any Way , Trafo manufacturers in my country don't give a damn about amperage
Thanks
0.5mm is american ga#24, i would normally use that wire for 0.5 to 0.8 amps in my traffos....gainclones have huge psrr's that the dc resistance of your traffo hardly matters....
so the 4amp spec quoted to you is a joke.....
if you want to use it for a gain clone, you can, the voltage will sag big anyway...your unloaded rails will be +/-40 volts......
for an lm3886:
Supply Voltage |V+|+|V−|
(No Signal) 94V
Supply Voltage |V+|+|V−|
(Input Signal) 84V
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