that is 1680 watts of loading, you need a traffo that has a 2800VA primary capacity...
in which case, yung need a core of 2 inch center leg stacked to 5 inches..
or if using a 2 1/4 center leg cores, stack is 4.25 inches...
look for Rey Luis in Caloocan, he can make one for you...
or you can reach me, 02-738-5635....
Wow! Big numbers! But why? For high power why not ClassD? If ClassD, then massive undersizing is allowed. For example my first big amp operated at +/-65 V, bridged, tested with 6 pcs of Eminence Omega Pro paralelled. (The 7th triggered the overcurrent protection.) The transformer was a toroid, weighted about 6 kg, was dead quiet, and got only hand-warm at soft clipping drive. Music power was about 4 kW.
2.8 kVA is enough to actually destroy a not very well built house in an efficient system.
2.8 kVA is enough to actually destroy a not very well built house in an efficient system.
well come to think of it, at such high power class D is really it....
or better yet, think pmpo where psu requirements are not that stringent....
in the philippines, we are a dumping ground of many junked electronics equipment
coming from developed countries....
so what to do with all of these surplus cores? make EI traffos....
or better yet, think pmpo where psu requirements are not that stringent....
in the philippines, we are a dumping ground of many junked electronics equipment
coming from developed countries....
so what to do with all of these surplus cores? make EI traffos....
I mean ClassD amplifier + small transformer.
PMPO in practice is a marketing bluff, some company specify a value that never comes out from the amplifier (5 times the real PMPO). In my amp real PMPO was 90A*125V=11kW, but it could drive the speakers at least as much as an ideally sized 2.7 kW (RMS) amplifier. (Rail voltage never went under 2*45V.)
The point is: a relatively small transformer can produce high power for short time, and if amplifier doesn't convert the majority to heat, then you can achieve much more sound pressure. Bass speakers have a hugh reactance in the used freq range, and a ClassAB convert reactive power to heat, while ClassD recirculates it.
PMPO in practice is a marketing bluff, some company specify a value that never comes out from the amplifier (5 times the real PMPO). In my amp real PMPO was 90A*125V=11kW, but it could drive the speakers at least as much as an ideally sized 2.7 kW (RMS) amplifier. (Rail voltage never went under 2*45V.)
The point is: a relatively small transformer can produce high power for short time, and if amplifier doesn't convert the majority to heat, then you can achieve much more sound pressure. Bass speakers have a hugh reactance in the used freq range, and a ClassAB convert reactive power to heat, while ClassD recirculates it.
What power output do you expect from your amplifier at what impedance, and what kind of amplifier is it? Probably 2*400 W at 4 ohm can be achieved with the first trafo mentioned.
I always start with measuring primary resistance. As a very fast and rough approximation P=0.05*V*V/R gives the maximal DC power output achievable in amplifier useage. For big trafos this is much higher than the rated power, for small ones this is lower or equal. But undistorted music is an unbelievably dinamic signal, peak to RMS current is always higher than 3 (sometimes over 30), so trafo will not be overloaded.
With ClassD amp the load ratio can be calculated from not current but apparent peak to effective power ratio, which is more than ~12 for any undistorted music signal and a typical woofer.
(This is why ClassD is not only a little more efficient as theoretical 100%/78% shows, but about 4 times more efficient at full music drive.)
Watts (peak) might be closer to your 5% rule. Then an additional power factor correction might bring things back to reality . most ppl want to know the approx. VA of their transformer.
seems sensible and simpler to bundle these addition 2 factors into your 0.05 correction term, given 95% of audio amps are using sinewaves and high capacitive loads and let the other 5% go to ***.
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What do you mean?
Because manufacturer wants to specify this (thermal considerations). But amplifiers don't care the temperature of the trafo.
Plus you can measure VA rating yery difficult, while a resistance measurement can be done in a minute, anywhere.
What 2 factors, and how? Can you tell values?
Do you mean 0.1%? Do you usally listen to sinewave? I don't. And I don't have electrostatic speaker either.
Please consider real music, and typical dynamic speaskers!
Typically leakage inductance is negligible, secondary resistance transformed to primary equals to primary resistance. With these in mind the simulation shows this:
Oh, maybe you referred to power line input as "sinewave"and puffer capacitor after rectifier as "load"? Sorry, it was not clear.
Hello sir,
I'm a student of UST and wanted to ask if do you know any other supplier of EI core of 2.5inch to 3inch center leg, in Raon? Or somewhere near?
I read from this forum post ( http://www.diyaudio.com/forums/powe...ansformer-philippines-base-3.html#post4504995 ) that you suggested Golden Mars but when we got there, their largest was 2inches only. Can you suggest any other sources of EI core? Thank you.
Finally made my own transformer
Hello everybody
After lot of handwork I build My transformer below its details
EI core size 32*46 mm = 216VA maximum
Line voltage is 230V/0.63A = 144Va
Output is 48V*3A = 144Va
turn per voltage 3.06
primary turn 703 with 24 SWG Dimeter mm 0.559
secondary turn 146 with 18 SWG Dimeter mm 1.22
Its working great i tested output with load its 45AC.
transformer is cool and no any humming sound. Now how to test current of transformer secondary because load required at list 100w.
Hello everybody
After lot of handwork I build My transformer below its details
EI core size 32*46 mm = 216VA maximum
Line voltage is 230V/0.63A = 144Va
Output is 48V*3A = 144Va
turn per voltage 3.06
primary turn 703 with 24 SWG Dimeter mm 0.559
secondary turn 146 with 18 SWG Dimeter mm 1.22
Its working great i tested output with load its 45AC.
transformer is cool and no any humming sound. Now how to test current of transformer secondary because load required at list 100w.
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look around in raon, in evangelista street, there are sellers there selling
these type of core...
measure the open circuit output voltage and the input voltage.
Apply you resistive load to BOTH windings.
At the same input voltage, measure your loaded output voltage. If possible include a low value reference resistor in series with your heavy load so that you can check the actual sinewave current flowing during the test.
Regulation = (Vopen-Vloaded)/Vloaded
If you had 48Vac when open and 45Vac when loaded with 24r0, then you have regulation = {48-45}/45 = 6.67%, when output current is 45/24 = 1.875Aac and your total output is {45+45V}*1.875A = 169W
But I think your core is too small to achieve this. I'd guess that your VA is somewhere between 100VA and 150VA and your regulation will be 7% to 10%.
Transformer regulaton is the amout the transformer voltage rises when the load is disconnected.
Starting with 45Vac and rising by 6.67% gives 45*(1+0.0667) = 48Vac
You need some high power resistors.
If the rated output voltage is 22Vac and you want 1.3A to pass, then you must attach a bank of high power resistors to that 22Vac winding AND attach a similar resistor to all other secondary windings.
The resistor bank needs to be 22V/1.3A = 16.9ohms, when it is hot. (if you expect a different current then use that value in your calculations.
You can't easily check the actual current when the resistor bank changes resistance value.
So I suggest you add a low value resistor try R'=0r1, that you know the value of very accurately, say <1%.
Add this in series with your resistor bank. Measure the voltage across the whole R+R'
So for your R=16r9 and R'=0r1 you have a measured secondary voltage of 22.08Vac and the Vr'=129.8mVac
The actual current is 129.8mVac/0r1 = 1.298Aac
the voltage is 22.08Vac.
The output power is 22.08*1.298 = 28.66W
The power dissipation in R is 1.298A²*16r9= 28.47W, it will get hot quickly.
The power dissipation in R' is 1.298A²*0r1= 168mW, use at least a 2W bank of 1% metal film resistors which have a tempco <=100ppm/C.
If the rated output voltage is 22Vac and you want 1.3A to pass, then you must attach a bank of high power resistors to that 22Vac winding AND attach a similar resistor to all other secondary windings.
The resistor bank needs to be 22V/1.3A = 16.9ohms, when it is hot. (if you expect a different current then use that value in your calculations.
You can't easily check the actual current when the resistor bank changes resistance value.
So I suggest you add a low value resistor try R'=0r1, that you know the value of very accurately, say <1%.
Add this in series with your resistor bank. Measure the voltage across the whole R+R'
So for your R=16r9 and R'=0r1 you have a measured secondary voltage of 22.08Vac and the Vr'=129.8mVac
The actual current is 129.8mVac/0r1 = 1.298Aac
the voltage is 22.08Vac.
The output power is 22.08*1.298 = 28.66W
The power dissipation in R is 1.298A²*16r9= 28.47W, it will get hot quickly.
The power dissipation in R' is 1.298A²*0r1= 168mW, use at least a 2W bank of 1% metal film resistors which have a tempco <=100ppm/C.
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Thanks AndrewT
I will try your suggestion. Can I use following Metal wire for output round few turn on ceramic this metal wire is Nickel Chrome Alloy use for heater
