That transformer is just .5 amp and if you asking for high current...that is bad!!!
Sorry, it is not .5 amp, it is 2.5amp...I getting old!
Sorry, it is not .5 amp, it is 2.5amp...I getting old!
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No, not at all a useless test. This constant power is what I need for my class A amplifier power supply.
Or, are you saying class A amplifiers are not 'good music amplifiers' ? 😀
And without any load it does not heat at all. So I do not suspect any shorted turns.
INDEL web page gives the same specifications of 50VA 2*12V 2*2.05A.
Maybe, just maybe, they put (accidentally or purposely) too thin wire and the heat is due to resistive losses ? 🙂
INDEL web page gives the same specifications of 50VA 2*12V 2*2.05A.
Maybe, just maybe, they put (accidentally or purposely) too thin wire and the heat is due to resistive losses ? 🙂
Yes exactly, camera shows only the radiated surface temperature. Because it's wrapped in multilayer plastic insulation tape (with poorish thermal resistance) the core temperature can be very high 😱
Actually, one can see from the IR image the hottest spots are on the inner edge where the tape is tightest with minimum of air between the layers and having highest thermal conductivity.
well, someone said that trafo could be dangerous to use now
wire insulation could have thousands of small cracks now
wire insulation could have thousands of small cracks now
Hi,
what is the resistor value you are using for the test? If you are doing the test with both winding in series then you need a resistor of 24/2.05 = 11.7 ohms and if it is in parallel then you need a resistor value of 12/4.10 = 2. 92 ohms.
what is the resistor value you are using for the test? If you are doing the test with both winding in series then you need a resistor of 24/2.05 = 11.7 ohms and if it is in parallel then you need a resistor value of 12/4.10 = 2. 92 ohms.
You'd probably also need to look at both primary and secondary transformer currents and check that the recharge current peaks in the primary do not freak out from saturation, hence 50Wrms with high crest factor causing higher losses than "the same" 50Wac (resistive sine power). And that's without losses of diodes and caps so its even more...
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You won't get 50W of continuous DC power from a 50VA transformer; 20W maybe. Could you clarify your test procedure? Where exactly are you measuring the RMS current: secondary AC or resistive load DC?Elias said:
According to the manufacturer, the transformer insulation is rated at 130 degrees C.
From their website: temperature class Ta 40B (ambient temp. 40ºC, insulation class B 130ºC)
From their website: temperature class Ta 40B (ambient temp. 40ºC, insulation class B 130ºC)
Elias, you are making a couple of fundamental mistakes...
Firstly, the transformer load is always measured and rated at the secondary, not after rectification. Someone mentioned crest factor - in order to drive approx 2A DC with 30mF smoothing your transformer true RMS output will be around 5A and peak current could be twice that, depending on the secondary DC resistance and other losses.
So you are overloading your transformer by 250%. Thats why its hot.
Secondly, a good way to be comfortable with your transformer load rating is to assume an output voltage regulation of 5% and never load it more than this. That is, a conservative no-load to full-load difference of 5%, measured at the secondary. This assures long safe life irrespective of the quality of manufacture or of the copper used.
John
Firstly, the transformer load is always measured and rated at the secondary, not after rectification. Someone mentioned crest factor - in order to drive approx 2A DC with 30mF smoothing your transformer true RMS output will be around 5A and peak current could be twice that, depending on the secondary DC resistance and other losses.
So you are overloading your transformer by 250%. Thats why its hot.
Secondly, a good way to be comfortable with your transformer load rating is to assume an output voltage regulation of 5% and never load it more than this. That is, a conservative no-load to full-load difference of 5%, measured at the secondary. This assures long safe life irrespective of the quality of manufacture or of the copper used.
John
Agree with previous. Cap bank derate VA rating about 40%. By rule o f thumb.
Limiting on transformers is power loss due to current through windings, I^2* R loss.
You are drawing currents equivalent to a 100W purely resistive load due to the crest factor of current peaks (capacitive load)
Limiting on transformers is power loss due to current through windings, I^2* R loss.
You are drawing currents equivalent to a 100W purely resistive load due to the crest factor of current peaks (capacitive load)
That could be it. But then the loss is not primarly due to winding resistance but from the core, since the crest factor affects on the core losses but not on the winding losses ?
I need a bigger transformer 😱
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I can't believe he's using it for a Class A amp.
Even the small Hiranga at 10W/Ch recommends a 160VA transformer as minimum and 250VA as better.
Might be OK for a 2W/Ch Headphone Amp.
Even the small Hiranga at 10W/Ch recommends a 160VA transformer as minimum and 250VA as better.
Might be OK for a 2W/Ch Headphone Amp.
You definitely need to get it down to warm. Inside an amplifier chassis you are generally cooking everything, caps and active devices primarily. If you can keep the inside of the case below say 45 degrees (80 max), then your project will live a lot longer.
Yes I made a fundamental mistake. I was trying to save some money by 'optimising' the transformer size. It was a bad idea
😀Loss will be mainly winding resistance, as you are overloading it. The charging pulses for the capacitor will have an RMS value much bigger than their average value.
When you told us in post 1 that you were loading the transformer with a resistor we assumed an AC load because we assumed you knew what you were doing and had correctly described it. In fact you are loading the transformer with a capacitor input rectifier which completely changes the situation. You sent us off down completely the wrong path so you can ignore most of what we said until we realised what you are actually doing.
When you told us in post 1 that you were loading the transformer with a resistor we assumed an AC load because we assumed you knew what you were doing and had correctly described it. In fact you are loading the transformer with a capacitor input rectifier which completely changes the situation. You sent us off down completely the wrong path so you can ignore most of what we said until we realised what you are actually doing.
Imagen in a class A amp (space heater) using this kind of transformer...I would put my stove away and cook right on top of amp😛
And that too ! What to do, I don't feel good to use potentially hasardous component ?
Save it for the New Year for some laboratory fire works 😛
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